<%BANNER%>

Reproduction of Eastern Bluebirds (Sialia sialis) in Relation to Farmland Management and Food Resources in North-Central...

Permanent Link: http://ufdc.ufl.edu/UFE0022316/00001

Material Information

Title: Reproduction of Eastern Bluebirds (Sialia sialis) in Relation to Farmland Management and Food Resources in North-Central Florida
Physical Description: 1 online resource (87 p.)
Language: english
Creator: Deluca, John
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: avian, biology, bird, bluebird, conservation, conventional, eastern, farms, land, management, natural, nestling, open, organic, pest, reproductive, sialia, success
Wildlife Ecology and Conservation -- Dissertations, Academic -- UF
Genre: Wildlife Ecology and Conservation thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Conservation ornithologists cannot responsibly promote farmlands as avian habitat without first evaluating the effects of farmlands on avian populations. In 2007, we examined the effects of land management (reduced-impact farms e.g., organic, conventional farms, and natural control areas) on the reproductive success and breeding behavior of the Eastern Bluebird (Sialia sialis). Farmland bluebirds began breeding earlier and produced more clutches and eggs than bluebirds in natural areas, but they produced the same number of fledglings over the breeding season. Differences in reproductive parameters between reduced-impact and conventional farms were minor. In 2008, we explored the mechanistic hypothesis that land management influences arthropod prey availability, which in turn influences bluebird reproductive success and breeding behavior. Prey was more bountiful but more unstable on farms over the course of the breeding season; prey biomass during the early breeding season was inversely correlated with first-egg-date; and higher variation in prey biomass inversely correlated with hatchling production during first broods. In comparison to natural areas, farmlands (especially reduced-impact) appeared to provide suboptimal but not necessarily poor habitat for breeding bluebirds. Future research should incorporate survivorship, mortality, and the effects of predation and human disturbance.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by John Deluca.
Thesis: Thesis (M.S.)--University of Florida, 2008.
Local: Adviser: Sieving, Kathryn E.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022316:00001

Permanent Link: http://ufdc.ufl.edu/UFE0022316/00001

Material Information

Title: Reproduction of Eastern Bluebirds (Sialia sialis) in Relation to Farmland Management and Food Resources in North-Central Florida
Physical Description: 1 online resource (87 p.)
Language: english
Creator: Deluca, John
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: avian, biology, bird, bluebird, conservation, conventional, eastern, farms, land, management, natural, nestling, open, organic, pest, reproductive, sialia, success
Wildlife Ecology and Conservation -- Dissertations, Academic -- UF
Genre: Wildlife Ecology and Conservation thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Conservation ornithologists cannot responsibly promote farmlands as avian habitat without first evaluating the effects of farmlands on avian populations. In 2007, we examined the effects of land management (reduced-impact farms e.g., organic, conventional farms, and natural control areas) on the reproductive success and breeding behavior of the Eastern Bluebird (Sialia sialis). Farmland bluebirds began breeding earlier and produced more clutches and eggs than bluebirds in natural areas, but they produced the same number of fledglings over the breeding season. Differences in reproductive parameters between reduced-impact and conventional farms were minor. In 2008, we explored the mechanistic hypothesis that land management influences arthropod prey availability, which in turn influences bluebird reproductive success and breeding behavior. Prey was more bountiful but more unstable on farms over the course of the breeding season; prey biomass during the early breeding season was inversely correlated with first-egg-date; and higher variation in prey biomass inversely correlated with hatchling production during first broods. In comparison to natural areas, farmlands (especially reduced-impact) appeared to provide suboptimal but not necessarily poor habitat for breeding bluebirds. Future research should incorporate survivorship, mortality, and the effects of predation and human disturbance.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by John Deluca.
Thesis: Thesis (M.S.)--University of Florida, 2008.
Local: Adviser: Sieving, Kathryn E.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022316:00001


This item has the following downloads:


Full Text

PAGE 1

REPRODUCTION OF EASTERN BLUEBIRDS ( SIALIA SIALIAS ) IN RELATION TO FARMLAND MANAGEMENT AND FOOD RESOURCES IN NORTH-CENTRAL FLORIDA By JOHN J. DELUCA A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2008 1

PAGE 2

2008 John J. DeLuca 2

PAGE 3

To my parents, Joe and Linda DeLuca 3

PAGE 4

ACKNOWLEDGMENTS The USDA Southern Region Sustainable Agricu ltural Research and Education (SSARE) graduate student grants program funded this re search, in part, with a dditional funding from the Department of Wildlife Ecology and Conservation. K.E. Sieving helped enormously with the design, implementation, and presentation of this research. P.C. Frederick and S.K. Robinson provided insight into resear ch design and valuable comments on ear lier drafts of this manuscript. M.C. Christman and R.J. Fletcher provided much-a ppreciated statistical a dvice. J. Altman, A. Arner, K. Church, C. Lord, S. Hicks, I. Star k, and J. Teagarden contributed significantly as volunteer field technicians. 4

PAGE 5

TABLE OF CONTENTS page ACKNOWLEDGMENTS ............................................................................................................... 4 LIST OF TABLES ...........................................................................................................................7 LIST OF FIGURES .........................................................................................................................8 ABSTRACT ...................................................................................................................... ...............9 CHAPTER 1 GENERAL INTRODUCTION ..............................................................................................10 2 EFFECT OF LAND MANAGEMENT ON THE REPRODUCTIVE SUCCESS OF A SONGBIRD OF OPEN LANDS ............................................................................................13 Introduction .................................................................................................................. ...........13 Farmland as Wildlife Habitat ..........................................................................................13 Farm Management and Avian Reproductive Success .....................................................14 Research Design ..............................................................................................................15 Methods ..................................................................................................................................17 Study Species ...................................................................................................................17 Study Sites and Nest-Box Placement ..............................................................................18 Data Collection ................................................................................................................19 Statistical Analysis .......................................................................................................... 20 Results .....................................................................................................................................21 Season-Level Reproductive Success and Breeding Behavior .........................................21 Clutch-Level Reproductive Success and Breeding Behavior ..........................................22 Nestling-Quality Indicators .............................................................................................22 Discussion .................................................................................................................... ...........23 Farmland Bluebirds Begin Nesting Earlier .....................................................................23 Farmland Bluebirds Reproduce Less Efficiently ............................................................23 Bluebird Reproductive Behavi or and Offspring Quality .................................................25 Differences between Reduced-Impact and Conventional Farms ....................................28 Farms as Suitable Habitat for Eastern Bluebirds .............................................................28 Future Research and Management Recommendations ....................................................31 3 REDUCED-IMPACT FARMING, PREY BIOMASS, AND THE REPRODUCTIVE SUCCESS OF EASTERN BLUEBIRDS ( SIALIA SIALIS ) ...................................................40 Introduction .................................................................................................................. ...........40 Wildlife-Friendly Farming ..............................................................................................40 Effects of Food Resource s on Avian Reproduction ........................................................41 Avian Reproduction on Wildlife-friendly Farmlands .....................................................42 Research Design ..............................................................................................................43 5

PAGE 6

Methods ..................................................................................................................................44 Study Species, Study Sites, and Nest-Box Placement .....................................................44 Prey Surveys ....................................................................................................................45 Prey Indices .....................................................................................................................47 Monitoring Bluebird Reproduction .................................................................................48 Statistical Analysis .......................................................................................................... 49 Results .....................................................................................................................................50 Prey Availability ..............................................................................................................50 Land Management and Bluebird Reproduction ..............................................................50 Discussion .................................................................................................................... ...........50 Prey Availability as a Mechanis m for Earlier First-Egg-Dates .......................................50 Prey Biomass Instability and Hatchling Production ........................................................51 First-egg-date and Season-l evel Clutch Production ........................................................53 Indications for Lower Reproductive Success on Farms ..................................................54 4 ARE WILDLIFE-FRIENDLY FARMS REALLY WILDLIFE-FRIENDLY? ..................65 APPENDIX A EFFECTS OF LAND MANAGEMENT ON THE REPRODUCTIVE SUCCESS OF A SONGBIRD OF OPEN LANDS ............................................................................................70 B REDUCED-IMPACT FARMING, PREY BIOMASS, AND THE REPRODUCTIVE SUCCESS OF EASTERN BLUEBIRDS ( SIALIA SIALIS ) ...................................................77 LITERATURE CITED ..................................................................................................................80 BIOGRAPHICAL SKETCH .........................................................................................................87 6

PAGE 7

LIST OF TABLES Table page 2-1 List of terms and definitions ............................................................................................. .33 2-2 Description of st atistical models ........................................................................................3 4 2-3 Results ................................................................................................................... .............35 2-4 Effect of land management and clutch order on hatching success ....................................36 3-1 Results ................................................................................................................... .............57 A-1 Raw data for pairs that laid a fourth clutch ........................................................................70 A-2 Site-level descriptive statisti cs, presented clutch by clutch ...............................................71 A-3 Rainfall patterns in North-central Florida ..........................................................................76 B-1 Site-level descriptive statistics ......................................................................................... ..78 B-2 Chapter 3 definitions ..........................................................................................................79 7

PAGE 8

LIST OF FIGURES Figure page 2-1 Effect of land management on fi rst-egg-day and interbrood lapse ....................................37 2-2 Effect of first-egg-day on season-level production of egg .................................................37 2-3 Effect of land management on bluebird reproductive success.. .........................................38 2-4 Effect of land management a nd brood-order on incubation period ...................................39 2-5 Effect of brood order on nestling body condition index. ...................................................39 3-1 Design logic for Chapter 3 ................................................................................................ .60 3-2 Effect of land manageme nt and pre-breeding GW prey biomass on first-egg-day ...........60 3-3 Effect of first-clutch WB prey instability (CV) and land management on first clutch hatchling production. .........................................................................................................61 3-4 Effect of land management on long-term prey biomass, long-term prey instability (CV), and first-clutch WB prey instability ........................................................................62 3-5 Effect of land management on firstegg-day, clutch production, and hatchling production, compared by year ............................................................................................63 3-6 Effect of first-egg-da y on clutch production ......................................................................64 8

PAGE 9

9 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science REPRODUCTION OF EASTERN BLUEBIRDS (SIALIA SIALIAS) IN RELATION TO FARMLAND MANAGEMENT AND FOOD RESOURCES IN NORTH-CENTRAL FLORIDA By John J. DeLuca December 2008 Chair: Kathryn E. Sieving Major: Wildlife Ecology and Conservation Conservation ornithologists ca nnot responsibly promote farmla nds as avian habitat without first evaluating the effects of farmlands on avia n populations. In 2007, we examined the effects of land management (reduced-impact farms [e.g ., organic], conventiona l farms, and natural control areas) on the reproductive success and br eeding behavior of the Eastern Bluebird ( Sialia sialis ). Farmland bluebirds began breeding earlier and produced more clutches and eggs than bluebirds in natural areas, but they produced the same number of fledglings over the breeding season. Differences in reproductive parameters between reduced-impact and conventional farms were minor. In 2008, we explored the mechanis tic hypothesis that land ma nagement influences arthropod prey availability, which in turn infl uences bluebird reproductive success and breeding behavior. Prey was more bountiful but more uns table on farms over the course of the breeding season; prey biomass during the early breeding season was inversely correlated with first-eggdate; and higher variation in prey biomass inversely correlated with hatchling production during first broods. In comparison to natural areas, farm lands (especially reduced-impact) appeared to provide suboptimal but not necessarily poor habitat for breeding bluebirds. Future research should incorporate survivorship, mortality, and the effects of pr edation and human disturbance.

PAGE 10

CHAPTER 1 GENERAL INTRODUCTION Promoting farmlands as bird habitat may at first seem attractive to both conservation planners and farmers (Jacobson et al. 2001; Green et al. 2005; Fisc her et al. 2008). However, we cannot responsibly encourage habitat management to increase birdlife on farmlands without first evaluating the suitability of farm land habitats in terms of bird population viability and health. Nevertheless, a variety of motivations exist to increase birdlife on farm s: Government and consumers are pushing for biodiversity-friendly food-production on farmlands (Grankvist and Beal 2001; Wild Farm Alliance 2005); farmers ofte n appreciate and foster non-pest birdlife on their lands (Jacobson et al. 2003); and as agricultural conversion of natural habitat continues to escalate, conservation planning processes increasi ngly identify farmlands as necessary to provide sufficient habitat for the protec tion of viable wildlife populations and communities (Tilman et al. 2001; Fischer et al. 2008). However, ecologi sts have only recently begun to understand how farmland management (e.g., organic and sustai nable farming [i.e., reduced-impact] vs. conventional farming techniques) influences th e composition, sustainability, and health of nonpest bird communities that use farmlands (H ole et al. 2005; Jones and Sieving 2006). For example, researchers have yet to compare av ian reproductive success among conventional farms, reduced-impact farms, and natural open lands. Ho wever, such comparisons are needed to gauge the quality of farmlands as habitat for sustaining healthy bird communities. Work presented here addresses this goal and provides insights rega rding the potential for avian conservation on farmlands. Chapter 2 presents a comparative analysis of the effects of land management on the reproductive success and breeding behavior of Eastern Bluebirds ( Sialia sialis ). Reduced-impact farms and conventional farms served as treatment groups and natural areas se rved as a control. 10

PAGE 11

We compared measures of reproductive su ccess and breeding beha vior among these landmanagement types, including: clutch, egg, hatchling, and fledgling production; nestling body condition and growth status; and first-egg-date, incubation period, and interbrood lapse. We did not detect major differences between bluebird reproduction on reduced-impact and conventional farms. However, farmland bluebirds (in general) began breeding ear lier and produced more clutches and eggs than bluebirds in natural areas, but they produced the same number of fledglings over the breeding season. In Chapter 3, we addressed the potentia l for food as a mechanism underlying these patterns. We assessed whether arthropod prey resources for bluebirds varied between farms and natural control areas, and whether prey resource differences between land management types were correlated with reproductiv e success and breeding behavior. We sampled arthropod prey using two distinct transect methods, and we used the data to calculate prey biomass and biomassstability indices. Dependent vari ables included clutch production, first-clutch egg and hatchling production, and first-egg-date. The amount of prey available in the early breeding season inversely correlated with first-egg-date. Prey resources were greater in amount but more unstable on farms. Prey instabil ity inversely correlated with fi rst-clutch hatchling production, and farmland bluebirds produced fewer first-clutch ha tchlings than those in natural control areas. In comparison to natural areas, farmlands (especially reduced-impact) appeared to provide suboptimal but not necessarily poor ha bitat for breeding bluebirds. In Chapter 4, we address if wildlife-friendl y farms are really wildlife-friendly. We recommend that future research focus on the effects of farm management on survivorship, mortality, and habitat preference in additi on to reproductive success, thereby allowing researchers to assess whether farms serve as habita t sources, sinks, or even ecological traps. We 11

PAGE 12

12 also recommend studying differences in predati on among farms and natural areas, as well as the effects of human disturbance on farmland wildlife. Finally, we suggest that future research occur over a larger spatial scale with a focus on open-land species of conservation concern.

PAGE 13

CHAPTER 2 EFFECT OF LAND MANAGEMENT ON THE REPRODUCTIVE SUCCESS OF A SONGBIRD OF OPEN LANDS Introduction Farmland as Wildlife Habitat Agricultural lands can be managed for both food and biodiversity production, and there is increasing pressure on many farmers to do so. The U.S. Department of Agriculture has released guidelines that require attention to biodiversity protection on organic farms (Wild Farm Alliance 2005). Moreover, increasingly healthand envi ronmentally-conscious consumers are creating market demands for produce branded with biodiversity-friendly certifications (e.g., Smithsoniancertified bird-friendly coffee; Grankvist and Beal 2001). Farmers themselves also show interest in increasing biodiversity on their lands. A survey of family farmers in North-central Florida indicated that most of them thi nk that birds could help control in sect pests and that they would like to attract such bi rds to their farms ( n=26 organic farms, 50 conventional; Jacobson et al. 2003). Finally, as global agricultur al expansion is projected to replace upward of one billion hectares of natural habitat duri ng the next fifty year s, conservationists are increasingly eyeing farmlands as critical habitat to augment insuffi ciently small protected areas (Tilman et al. 2001, Fischer et al. 2008). The argument is that if ag riculture can provide some use to many species and suitable habitat for a few, then it could serve as an ecologi cal buffer around natural areas to boost their biodiversity-holding capacity (P hillips 2002). Natural habitats and landscape mosaics that are fragmented by agri culture, however, often do not sustain healthy ecological communities. For example, various studies from different biomes document high rates of nest failure for many interior-forest oblig ate birds in fragments surrounded by agriculture (Ford et al. 2001, Rodewald and Yahner 2001 a and b, Albrecht 2004, Knutson et al. 2004, Peak et al. 2004, Tewksbury et al. 2006). Fragments suffer higher rates of 13

PAGE 14

exotic species invasion and nest predation (Rodewald and Yahner 2001 b Tewksbury et al. 2006) and generally diminished species richness and evenness of native communities (Rodewald and Yahner 2001 b). Though farmlands may create population sinks or ecological traps for forestrequiring species (e.g., Wood Thrush [Hylocichla mustelina ], Fauth 2001, Zuria et al. 2007), current thinking is that they may provide suitable habitat for species that can tolerate, or that prefer, lands where native ecosystems have been cleared for human land uses involving natural resource production (e.g., for food or fiber). Indeed, a central fo cus in conservation research is to characterize the potent ial values of wildlife-friendly fa rms (Green et al. 2005, Fischer 2008) and farming landscapes more gene rally as biodiversity buffers (D aily et al. 2001, Sekercioglu et al. 2007). Farm Management and Av ian Reproductive Success Avian reproductive success typi cally appears to be higher on organic and other reducedimpact farms than on conventional farms (see Table 2-1 for definitions, Patnode and White 1991, Hatchwell et al. 1996, Wilson et al. 1997, Bishop et al. 2000 a and b, Brickle et al. 2000, Mayne et al. 2004 and 2005, Bouvier et al. 2005, Britschgi et al. 2006, Hart et al. 2006 but see Graham and Desgranges 1993). Such variation suggests that some conventional farming operations may not provide useful or productive habitats for native birds, because reproductive success is one of the strongest indicators of habitat quality (Hall et al. 1997). However, such variation also suggests that farm management techniques can be developed to improve both species richness and habitat quality for native species on agricultural lands. It is not enough to implement management tec hniques that simply increase wildlife use or species richness; suitable on-farm habitats must also provide cri tical resources that sustain or augment robust reproduction and population health (H all et al. 1997). Ecological traps can easily be created on farms if species are attracted to use on-farm habitats for foraging (e.g., Jones and 14

PAGE 15

Sieving 2006) or for reproduction (e.g., Mols an d Vissar 2002) but suffer greater mortality or depressed reproduction as a result (Schlaepfer et al. 2002). To offer greater understanding of how habitat quality for native birds can vary on farms, we focused this study on the cavitynesting Eastern Bluebird ( Sialia sialis ), an aesthetically popular sp ecies of open lands known to consume pest insects (Jones et al. 2005). We erected nest-boxes and compared reproductive success and nestling health among conventional a nd reduced-impact farms and natural control areas (see Table 2-1 for definitions). Our desi gn allowed assessment of bluebird reproductive success on farmlands under different management regimes against reproduction of birds breeding in supposedly high-quality, natural habitat. Detailed analysis of bluebird reproductive parameters allowed us to addresses potential negative aspects of farm land bird conservation efforts involving nest-box provisioning on farmlands. Research Design We tested the hypothesis that land mana gement affects Eastern Bluebird (Sialia sialis ) reproductive success, breeding behavior, and nest ling health in a comparative-observational study design. Reduced-impact farms and conventi onal farms represented treatment groups, and natural areas served as controls (Table 2-1). We placed approximately 100 nest boxes evenly across both farm treatments and 30 nest boxes in na tural control areas. Fo r nests established in these boxes, we monitored trad itional indicators of avian re productive success, including: production of clutches, eggs, hatchlings, and fledglings; hatching success; and nestling body condition and pre-fledging growth status (Clark and Martin 2007, Jakob et al. 1996). Since bluebirds lay multiple broods per breeding season (Gowaty and Plissner 1998), we monitored all nest attempts on study sites in 2007 so that we could account for expected declines in reproductive success measures that typically occu r over the course of multiple broods over the course of a full breeding season (Slagsvold 1984, Smith et al. 1987, Tinbergen 1987, Gustafsson 15

PAGE 16

et al. 1994, Richner et al. 1995, Deerenberg et al. 1997, Nilsson and Svensson 1996, Raberg et al. 1998). We also documented key breeding behaviors known to influence reproductive success, including first-egg-date, interbrood lapse, and incubation period (see Table 2-1, Blanco et al. 2003, Hepp et al. 2006, Moller 2007). A potential mechanism underlying differen ces in reproductive success and breeding behavior across treatments could be due to differences in food abundance, quality, and predictability, and/or the dire ct effects of pesticides. B ecause reduced-impact farms lack powerful, synthetic pesticides while also usi ng mixed-crop planting methods, they may promote the species richness and abundance of arthropods, providing greater protein-rich food resources necessary for breeding birds than conventional fa rmlands (Feber et al. 1997, OLeske et al. 1997, Jones et al. 2005, Britschgi et al 2006, Jones and Sieving 2006). The limited use or absence of pesticides on reduced-impact farms may also preven t negative, direct effect s of pesticides seen on some conventional-farms (e.g., Patnode and White 1991, Bishop et al. 2000 a and b, Mayne et al. 2004 and 2005, Bouvier et al. 2005). Though we do not test these mechanisms with measures of insects and pesticides in th is study, previous work supports the operating assumption that food resources and direct pesticide effects are likely mechanisms underlying differences in reproductive success and breeding behavior, and th at both factors vary predictably across our treatment and control sites (Patnode and Wh ite 1991, Korpimaki 1992, Phillips et al. 1996, Bishop et al. 2000 a and b, Valkama et al. 2002, Mayne et al 2004 and 2005, Bouvier et al. 2005, Davis et al. 2005, Lindstrom et al. 2005). We th erefore predicted that bluebirds on reducedimpact farms would produce more clutches, eggs, hatchlings, and fledglings than bluebirds on conventional farms, and that their nestlings would be in better body condition and more 16

PAGE 17

advanced development just prior to fledging, su ggesting a higher probabi lity for post-fledging survival (Blanco et al. 2003, Hepp et al. 2006, Jakob et al. 1996). To our knowledge, we are the first to compare the reproductive succe ss of open-land birds on reduced-impact and conventional farmlands to the same species breeding in natural habitats of comparable vegetative structure. Therefor e, predictions concerni ng reproductive success of bluebirds on farms versus our natural cont rol areas were not obvious, though it seemed reasonable to expect that reproduction on reduced-i mpact farms would be closer to natural areas than conventional farms. However, an important subsidy that farmers pr ovide is irrigation and fertilizer, and this may affect bluebird repr oductive success and behavi or. The late-winter planting season in Florida typically falls with in the dry season ( NOAA 2008); irrigation and fertilizer during this period artificially supports plant growth, which in turn could spur flushes of invertebrate prey on farms before natural areas Since early flushes of food resources are common proximate causes of nesting initiation in breeding birds (Martin 1987, Nooker et al. 2005, Pimentel and Nilsson 2007), we predicted th at bluebirds may start breeding earlier on farms than natural areas, and this could influe nce subsequent reproductive success measures (Elmberg et al. 2005, Nemeckova et al. 2008, Verhulst and Nilsson 2008). Methods Study Species The Eastern Bluebird is a ch arismatic, primarily insecti vorous, ground-gleaning, secondary cavity-nester of open lands. Females lay multiple broods and are the only parent that incubates, though males feed incubating females (Gowaty a nd Plissner 1998). Beca use of the species penchant for using nest-boxes, bluebird reproduction is commonly studied and monitored by ornithologists and lay birders alike. The speci es was once uncommon in North America, but its populations have grown considerably due to community-based conservation efforts involving 17

PAGE 18

nest-box provisioning. However, it remains threatened in parts of its range (Gowaty and Plissner 1998). It is a logical choice as a study-species because 1) it is one of the three most common species found foraging on farmlands in North-centra l Florida (Jones et al. 2005), 2) it specializes on arthropods throughout the enti re year (Gowaty and Plissner 1998), and 3) it takes readily to nest-boxes that can be strategically placed in different habitats for comparative analyses (Gowaty and Plissner 1998). Study Sites and Nest-Box Placement We conducted this research in North-central Florida (Alachua and Putnam Counties) during the entire breeding seas on of 2007 (February-August). We erected nest-boxes on six conventional farms, eight reduced-impact farms, and at four natural c ontrol areas within the Ordway-Swisher Biological Station property (> 3760 ha in area, s ee Table 2-1 for descriptions). Bluebird nest boxes have been provided and m onitored in this protected area since the mid 1990s with sustained high levels of nest box occupancy and reproductive success (KES, personal observation ). Most reduced-impact farms were USDA-certified organi c operations or were managed in line with organic standards (b ut without certification) Cropping systems used in this study and that are charac teristic of the region are describe d fully in Jacobson et al. (2003) and Jones et al. (2005). We asked growers about their use of synthetic pesticides before the beginning of field work. Three of eight reduced-i mpact farmers used synthetic pesticides (only one used insecticides), but they did so sparin gly, only on certain crops at certain times. All participating conventional farmers applied insectic ides and other pesticid es on the entirety of their crops in multiple applications (for beans, corn, strawberries, tobacco, and/or melons, depending on the farm; we did not ask farmers the ex act types or amounts of pesticides that they used). 18

PAGE 19

No nest-box was placed less than 70 m from its nearest neighbor. Nest-boxes on farms were placed within 5 m of the edges of farm-fields (barren, fall ow, or with active crop growth), and within at least 300 m of fiel ds with actively growing crops at some point in the season. Nest-boxes in all treatments were within 50 m of protective cover and pe rching substrates used by bluebirds (e.g., hedgerows, windbreaks, forest). In order to control for predation, we mounted nest-boxes on narrow, metal poles (approximately 1.5 m high). We greased the poles when birds laid eggs and maintained these grease barr iers throughout nesting (USDA Natural Resources Conservation Service 1999). If predators overcame this deterrence, then signs left in the grease or on the boxes allowed detection of predation events. We eliminated data from predated nests from statistical analys es as appropriate. Data Collection We monitored nest-boxes approximately ever y four days, when we recorded how many eggs and/or nestlings were in th e nest, and the estimated age of nestlings (using the criteria of Gowaty and Plissner 1998). We consider a bird's fi rst day of life as age, Day 1. We identified a pair's second or third clutch if it was laid wi thin the same box (typically the case) or if it was within 300 m of the pair's last nest-box and 13 weeks after the pair's last brood fledged. Confusion with neighboring pa irs within a site was easily prevented because pairs would normally re-nest in the same box and neighbors t ypically had non-concurrent nesting cycles. We calculated first-egg-date, incubation period, and interbrood lapse from these data (see Table 2-1 for definitions). Earlier first-egg-da tes should correlate with higher clutch production over the breeding season, as bluebirds will presumably have more time to lay more clutches. Shorter incubation periods correla te with higher nestling quality (Blanco et al. 2003, Hepp et al. 2006). Eggs should take less time to hatch wh en females spend more time on the nest, and females should spend more time on the nest when they are able to forage more efficiently, they 19

PAGE 20

are fed more often by their mates, and/or food res ources are better. Birds that take less time to re-nest may exhibit higher reproductive success, so interbrood lapse may serve as another indicator of the quality of breed ing habitat (Moller 2007). We only included pairs that fledged at least one nestling from their first clutch in the calculation of interbrood lapse. We uniquely identified nestli ngs by painting nail-polish on thei r claws during each visit. After approximately 6 days of age, we tagged them with unique color band-combinations. We recorded a nestlings weight (+ /1.0 g) and left-tarsus length (+/0.1 mm, measured from the distal end of the tarsus to the second scale, counting toward th e claws) at each visit. We recorded wing cord (+/0.5 cm) and the length of both tarsi at th e pre-fledging stage (i.e., at or above 14 days of age). We calculated nest ling Body Condition Index (BCI) and pre-fledging body-growth index (BGI) from these data (see Table 2-1). Both measures are standard indicators for nestling quality (Jakob et al. 1996, Navara et al. 2005). We classifi ed nestlings into six categories, as follows: 3 days < Category 1 < 5 days < Category 2 < 8 days < Category 3 < 10 days < Category 4 < 12 days < Category 5 < 14 days. Category 6 included nestlings at or above 14 days of age, and BGI analysis only included nestlings from this category. Statistical Analysis Analyses were conducted using general linear and ge neralized linear mixed models in SAS 9.1 (see Table 2-2 for model descriptions). Wh enever using a normal distribution, we first ensured that data met assumptions of normality using q-q plots and those of homoscedasticity using Levenes Test. We used Tukeys test for pairwise comparisons (al pha=0.05). We used the Kenward-Roger method for calculating degrees of freedom. All but one pair of bluebirds in the natural control failed to produ ce three clutches, and many birds in the farm treatments laid three. We therefore conducted two types of analyses for the clutch-level and nestling-level data (Tables 21 and 2-2). All-treatments analyses included 20

PAGE 21

all three treatments, with just clutches/broods 1 and 2, and Far ms-only analyses included only conventional and reduced-impact farms (i.e., we e liminated the only pair of natural control birds that laid a third clutch), with all three clutches/broods includ ed. Two pairs on conventional and reduced-impact farms laid a fourth clutch, but we could not analyze these da ta at the clutchor nestling-level (see Table A-1 for raw data). We could not nest bluebird pairs by site-ID in our models; covariance matrices necessary for analys is could not be calculated due to insufficient data at the site-level (e.g., seve ral sites only had 1-3 nesting pairs; Table A-2). However, if there is high between-site variation wi thin each treatment category, any land management differences that are observed should be very strong, making our analyses cons ervative in nature. Results Season-Level Reproductive Success and Breeding Behavior Twelve of twenty models produced signifi cant results (alpha=0.05; see Table 2-3 for detailed results of all models). First-egg-date was earlier and interbrood lapse shorter on farms, in general, than on natural control areas (Fig ure 2-1; Table 2-3). First-egg-date and land management were both related to season-level production of eggs. Earlier first-egg-dates corresponded with bluebirds that produced mo re eggs over the breedi ng season (Figure 2-2; Table 2-3), and both farm treatment s hosted birds that laid more eggs than in the natural control area (Figure 2-3; Table 2-3). A lthough not statistically significant, the pro duction of 3 clutches by many farmland bluebirds versus 2 by those on na tural sites appears to be a biologically significant difference in clutch production (Table 2-3), as th e production of third clutches requires a greater expenditure of time and ener gy for egg production and incubation. Many pairs of bluebirds went on to lay a third clutch on re duced-impact and conventional farms (Table 2-3). On the contrary, only one pair of bluebirds in the natural control area pr oduced a third clutch (and this was only its second brood). 21

PAGE 22

Clutch-Level Reproductive Success and Breeding Behavior As mentioned earlier, we ran tw o different types of clutch-l evel analyses, one with all treatments but just the first two clutches (All-t reatments analysis), and another with just farm treatments compared across the first three clutches (Farms-onl y analysis). All-treatments analyses that land management correlated with hatchling production and ha tching success, with bluebirds on conventional farms producing sign ificantly fewer hatchlings and exhibiting significantly lower hatching success than those in natural control areas (Figure 2-3; Tables 1-4 and 1-5). Bluebirds on reduced-impact farms inc ubated for significantly le ss time (Figure 2-4; Table 2-3) compared to bluebird s on natural control areas. Sec ond clutches, regardless of land management, took less time to incubate than first clutches (Figure 2-4; Table 2-3). Bluebirds on reduced-impact farms also produced fewer fledglings in their second clutch than in their first (Figure 2-3; Table 2-3). Farms-only analyses revealed the following pa tterns for birds nes ting on conventional and reduced impact farms. Clutch-order correlate d with hatchling and fledgling production, with bluebirds on both farm types producing significan tly fewer hatchlings and fledglings in their third clutch than their first (F igure 2-3; Table 2-3). Hatching success was also much lower in third than first clutches (Figure 2-3; Table 23). Farms-only results confirmed and extended the all-treatments results in regard to the correlation of clutch-ord er and incubation period; second and third clutches took significantly less time to inc ubate than first clutches (Figure 2-4; Table 23). Nestling-Quality Indicators The only significant nestling-level result ca me from Farms-only analysis of BCI. Nestlings from second and third broods exhibite d significantly lower body condition than those from first broods (Fi gure 2-5; Table 2-3). 22

PAGE 23

Discussion Farmland Bluebirds Begin Nesting Earlier Land management clearly affects the repr oductive success and breeding behavior of Eastern Bluebirds. Bluebirds in both farm treatme nts laid their eggs much earlier than those in natural control areas, confirming a central predic tion about the possibility that farm management (e.g., presence of irrigation, fertil izer, crop vegetation, and/or di fferent prey resources) could spur earlier breeding. Also, pairs that produced their first clutch earlier went on to produce more clutches over the breeding s eason, confirming a pattern we assumed would occur based on previous documentation of the reproductive advantage of early nesting (Figures 1-1 and 1-2; Table 2-3; Elmberg et al. 2005, Ne meckova et al. 2008, Verhulst and Nilsson 2008). It is likely that differences in prey availability during the months of February and March may have driven earlier first-egg-dates, though we did not test that mechanism in this study. These months corresponded to the dry season of our study regio n, when natural areas lacked green vegetation and moisture (NOAA 2008; JJD personal observation ). Most participatin g farmers grew crops year-round on our farmland study sites, except July to September, and most of them irrigated and fertilized their fields throughout the dry season (JJD personal observation ). The earlier presence of green vegetation due to fertilizer and wa ter on farms may have allowed arthropod prey populations to approach adequate levels to spark earlier breeding in Eastern Bluebirds on these lands (Martin 1987, Nooker et al. 2005, Pimentel a nd Nilsson 2007). However, despite an earlier start and a greater production of clutches and eg gs on farms, net fledgling production of farmland birds was no different than bi rds nesting on natural areas. Farmland Bluebirds Reproduce Less Efficiently First-egg-date and land management both aff ected clutch production (and consequently, total egg production; Figures 1-2 and 1-3; Table 2-3). Bluebird pairs in both farm treatments 23

PAGE 24

produced more eggs over the breeding season than bl uebirds in natural cont rol areas (Figure 2-3; Table 2-3). However, bluebirds in all land ma nagement groups ended up producing statistically similar numbers of hatchlings and fledglings at the season-level of analysis (Figure 2-3; Table 23). While our models did not detect a treatmen t-by-clutch-order interact ion in hatching success, we did detect significant declines in hatching success and fledgli ng production over the course of the 2007 breeding season on the two farmland treatments (Figures 1-3 and 1-5; Table 2-3). Given that over the entire breeding season of 2007, 24-30% of eggs on farms were produced in third and fourth clutches (versus only 4% of e ggs produced after the s econd clutch on natural control areas), a significant dec line in hatching success with clut ch order on farms explains how relatively greater seasonal clutch and egg production on farms did not result in greater fledging success on farms relative to natural areas (Table 24). Thus, on farmlands in our study, an early start on breeding did not result in greater seasonal production of young as has been observed in various avian taxa in natural habitats (Elmberg et al. 2005, Nemeckova et al. 2008, Verhulst and Nilsson 2008). The mechanism behind this relative reproductive inefficiency is likely to be linked to differences in availability or access to prey resources on farms in comparison to natural areas. As crops are sowed and harvested and the fa llowing of fields waxes and wanes, arthropod communities may cycle more dramatically on farm s than on natural sites (Nebel and Wright 1993). Alternatively, the day-to-day activity of farmers may induce reproductive inefficiency on farms. Perhaps the noise and/or movement of pe ople, tractors, and trucks near nest-sites disturb breeding bluebirds on farms, thereby decrea sing reproductive success (Yasue and Dearden 2006). 24

PAGE 25

Bluebird Reproductive Beh avior and Offspring Quality Bluebirds in both farm treatments exhibited a sh orter interbrood lapse than those in natural control areas (Figure 2-1; Table 2-3), and in all-treatments analyses we found that bluebirds on reduced-impact farms spent much less time incubati ng than those in natura l control areas (Figure 2-4; Table 2-3). Both shorter interbrood lapse and shorter incubation times have been linked to higher quality offspring, suggesti ng that the greater effort of bluebirds on farms may result in similar numbers of young, but young of higher quality (at least early in the breeding season; Blanco et al. 2003, Hepp et al. 2006, Moller 2007). To date, few studies have examined the eff ects of interbrood lapse on reproductive success, but Moller (2007) detected an inverse correlation between inte rbrood lapse and the strength of nestling immunity in first broods of Barn Swallows ( Hirundo rustica ), another cavity-nesting passerine of open lands. This fi nding suggests that first-brood ne stlings in both farm treatments may have had higher immunocompetency than their natural counterparts, re sulting in a survival advantage for the young birds (Moller 2007). Howe ver, extrapolation is not straightforward because 1) no causal link has been establishe d between interbrood lapse and immunocompetency (only correlation) and 2) in our study, various other factors coul d reasonably affect immunocompetency. For example, the use of ch emical pesticides on conventional farms may actually compromise nestling immunocompetenc y, neutralizing or overriding any potential effects of a shorter interbrood lapse (Patnode and White 1991, Bishop et al. 2000 a and b, Mayne et al. 2004 and 2005, Bouvier et al. 2005). Ho wever, while we cannot conclude anything without data on immunocompetency of bluebird young in our study, we can propose a hypothesis that farmland bluebird br eeding behavior (in this case ra pid re-nesting) may be able to offset lower reproductive efficiency over the season by increasing the quality of nestlings, especially those produced ear ly in the br eeding season. 25

PAGE 26

On the same theme, shorter incubation peri ods have been linked to the production of higher quality young; specifically, hatchlings wi th greater residual reserves and potentially increased survival (Blanco et al. 2003, Hepp et al 2006). All-treatments analysis revealed that bluebirds on reduced-impact farms exhibited shorter incubation periods than those in natural control areas. Since a) the data set in this analysis was dominat ed by nestlings from first broods, b) BCI values of first-brood nestlings were re latively high (Figure 2-4; Table 2-3), and c) incubation period has been shown to have an inverse relationship with nes tling quality (Blanco et al. 2003; Hepp et al. 2006), we th ink that bluebirds from first broods on reduced-impact farms may have been of higher quality than their counterparts in natural cont rol areas. If true, then this may offset, at least in part, th e negative fitness effects of re productive inefficiency on reducedimpact farms. We cannot find much support to extend such conclusions to second and third broods on farms. Bluebirds incubating second and third broods did so for less time than first broods (Figure 2-4; Table 2-3) However, unlike nestlings from first broods, body condition indices of secondand third-brood nestlings we re very low (Figure 2-5; Tabl e 2-3). This indicates that these nestlings were of poor quality (Jakob et al. 1996) and that their relati vely shorter incubation periods had more to do with environmental f actors (as opposed to somatic or parental care factors). Indeed, later clutches may have taken less time to incubate because of higher ambient temperatures that can speed development duri ng incubation (Hepp et al. 2006) but may also degrade embryo health (Londono et al. 2008). Despite breeding behavior that suggests that farmland bluebirds might have produced some higher quality offspring than bluebirds in natura l areas, we think it is highly unlikely overall. First, our statistical models did not detect a significant interaction between treatment and BCI, 26

PAGE 27

nor did clutch-order have an effect in all-treatments analys is broods 1 and 2 showed no difference in nestling body condition. Second, when we restricted clutch-l evel analyses to only farms (looking across all clutches), we found th at farmland nestlings from second and third broods exhibited much lower body condition than those from first broods (Figure 2-5). Altogether, this suggests that bluebirds in natu ral control areas produced high-quality nestlings in both of their broods, but farmland bluebirds only produced high-qual ity nestlings in their first broods. Since over half of all farmland offspri ng were produced in second and third broods (49 of 85 on conventional farms and 90 of 161 on reduced-impact farms), any immunocompetency or other survival advantages possibly conveyed to farmland fle dglings earlier in the breeding season via shorter incubation or in ter-brood periods are unlikely to outweigh the effects of such a high proportion of nestlings in re latively poor body condition. Finally, according to life-histor y theory, prior reproductive e ffort lowers a females body condition which, in turn, negatively affects the deve lopment of eggs and the survival of nestlings in future breeding attempts (Slagsvold 1984, Sm ith et al. 1987, Tinbergen 1987, Gustafsson et al. 1994, Richner et al. 1995, Deerenberg et al. 1997, Nilsson and Svensson 1996, Raberg et al. 1998). The declines in hatching success, hatc hling production, and ne stling BCI of farmland bluebirds in later clutches are all in line w ith basic predictions based on life-history theory (Figures 1-3 and 1-5; Table 2-3). But these dec lines were only evident or detectable in farmland birds because they laid so many clutches duri ng the 2007 season. These same declines in life history parameters would likely have been obser ved on natural areas had bluebirds nesting there not stopped after their second clutches. Due to th e necessity of nesting more times later in the season to boost overall offspring production on farmla nds, predictable late season declines in egg viability and offspring BCI weighed more heavily on season-level reproductive success 27

PAGE 28

measures. Bluebirds on farms worked harder for (a t best) the same, or very likely worse, results than bluebirds breeding on natural areas. This wa s especially true for bluebirds on conventional farms, given that clutch-level analyses revealed that these birds exhibi ted much poorer hatching success and produced many fewer hatchlings than blue birds in natural control areas, especially in their second clutch (Fig ure 2-3; Table 2-4). Differences between Reduced-Imp act and Conventional Farms Bluebird reproductive success or breeding behavior did not differ substantially between reduced-impact and conventional farms. Bluebi rds on conventional farms produced significantly fewer hatchlings than those in na tural control areas at the clutch -level of analysis, but such a difference was not detectable for bluebirds on reduced-impact farms (Tables 2-3 and 2-4). Bluebirds on reduced-impact farms took significantly less time to incubate their early clutches than bluebirds in natural control areas, but blue birds on conventional farms did not (Figure 2-4; Table 2-3), potentially indicati ng that first-brood nestlings on reduced-impact farms were of especially high quality (see above). However, we did not detect significant advantages of reduced-impact over conventional farms as avia n breeding habitat, in terms of nestling production or condition, whereas ot her studies have (Patnode and White 1991, Hatchwell et al. 1996, Wilson et al. 1997, Bishop et al. 2000 a and b, Brickle et al. 2000, Mayne et al. 2004 and 2005, Bouvier et al. 2005, Britsch gi et al. 2006, Hart et al. 2006 but see Graham and Desgranges 1993). Farms as Suitable Habitat for Eastern Bluebirds One season of data cannot fully address the que stion of whether farmlands in North-central Florida should be considered high quality habitat for breeding Eastern Bluebirds. High quality (or suitable) habitat has been defined in various ways (Hall et al. 1997), but the most essential elements include provision of critical needs (cov er, food, water, and resources for reproduction) 28

PAGE 29

sufficient to sustain viable populations (productiv ity exceeds mortality) over time (Van Dyke 2005). Only a full sample of annual variation in environmental and demographic parameters affecting health and productivity can indicate whether lifetime fitness of bluebirds nesting on farms is sufficient to sustain healthy populati ons. The magnitude and direction of annual variation in weather, food avai lability, and associated reproduc tive success varies greatly among years for a variety of bird species (Korpi maki 1992, Phillips et al 1996, McCleery et al. 1998, Rodl 1999, Valkama et al. 2002, Davis et al. 2005, Lindstrom et al. 2005). Rainfall in 2007 for North-central Florida was well below the normal range of rainfall values for the region (Table A3; FAWN 2008). Relative reproductive output on fa rms versus natural areas may vary in degree and direction along with rainfall variation (e.g., McCleery et al 1998). Based on this study, we therefore conclude that in one relatively dry year, reproductive output (number of offspring per pair) can be similar on farms and natural areas in this region (though fa rmland birds invested greater reproductive effort) and overall nestling quality may have been lower on farms. We excluded predation as a potential factor (see Methods), so the best explanation for differences between our treatments lies in food resources (Korpimaki 1992, Phillips et al. 1996, Valkama et al. 2002, Davis et al. 200 5, Lindstrom et al. 2005). In pa rticular, the ea rlier first-eggdates that we observed on farms were probably due to earlier prey av ailability (Martin 1987, Nooker et al. 2005, Pimentel and Nilsson 2007). I rrigation and fertilizer inputs causing earlyseason presence of green crop vegetation (in Februa ry-April) may instigate earlier and faster pest (prey) population growth on farms than natural areas ; the latter typically c ontinue to be exposed to dry season conditions until late May in th is region (NOAA 2008). Higher food availability during the early breeding season may also serv e as the mechanism behind shorter incubation 29

PAGE 30

periods and interbrood lapses that we observed on reduced-impact farms (e.g., Nooker et al. 2005). Farmland bluebird pairs may reproduce less e fficiently because prey populations may be more volatile on farms. Farm-f ields constantly change; farmers plant and harvest crops and leave certain fields fallow while they till others Such an unstable vegetative landscape may cause prey populations that rely on crops or fa llow fields to go through population explosions and crashes (Nebel 1993). In a companion study, we explore hypotheses that farming affects prey resources and, in turn, avian reproductive success (see Chapter 3). Lastly, assessing the suitability of farmland habitats requires a large spatial scale perspective. Our results suggest that if bluebirds were constr ained to breed on farmlands over their lifetimes, then th e higher effort associated with more broods per season would reduce lifetime fitness. Life history theory indicates that higher cu rrent reproductive effort should decrease future reproductive output and parent al survival (Slagsvold 1984, Smith et al. 1987, Tinbergen 1987, Gustafsson et al. 1994, Richner et al. 1995, Deerenberg et al. 1997, Nilsson and Svensson 1996, Raberg et al. 1998). Under this theo ry, we would expect that bluebirds in natural areas will exhibit greater future reproductive su ccess and survive longer because they produced the same number of fledglings with less effort (Figure 2-1; Table 2-3). However, we have no reason to suspect that bluebird populations are restricted to br eeding on farms in North-central Florida because 1) natal philopatry in this species is less than 15% (G owaty and Plissner 1998), 2) the landscape in the region maintains a hi gh proportion of area in unc ultivated and natural habitats, and 3) most farms are too small to support self-sustaining popu lations (Jones et al. 2005, Jones and Sieving 2006). Thus it is likely that in this re gion, bluebirds do not currently 30

PAGE 31

suffer population-level effects of reduced reproduc tive efficiency, such as we detected, over the long term. Future Research and Management Recommendations This study is among the first to compare East ern Bluebird reproducti on on natural versus human-managed lands (Mayne et al. 2004 and 2005, LeClerc et al 2005, Stanback and Seifert 2005, Kight and Swaddle 2007). Only in the compar ison of natural habitats to human-managed lands can we understand how land management affects native species. Many studies have documented occupancy and use of farmlands by birds (e.g., Daily et al 2001, Jones and Sieving 2006), foraging activity (e.g., Jones et al. 2005, Seke rcioglu et al. 2007) a nd reproductive success on farmland habitats (e.g., Sekercioglu et al. 2007 ). Others have shown how wild birds can improve agricultural productivity through consumption of insect pests (Greenberg et al. 2000, Mols and Visser 2002, Phillips 2002, Hooks et al 2003, Jones et al. 2005, Borkhataria et al. 2006). However, true integration of bird cons ervation with agricultur al production must go further than simply attracting more species to farmlands and promoting biodiversity for the purpose of promoting food producti on. We must document that farming systems can provide good quality habitat for wild birds. Future research addressing these issues should 1) occur at the largest scales practical, in order to capture populati on-level implications of land management; 2) occur over several years if possible; 3) assess food resource and mortality factors associated with land management regime s; and 4) compare, as we did, reproductive performance on farms against performance on naturally-occurring su itable habitats with long histories of occupancy and successful reproduction of the species in question. It is not enough to document wildlife use of human-dominated landscap es; fostering true integration of wildlife conservation in land management schemes requires documentation of population viability (Hall et al. 1997). 31

PAGE 32

32 That being said, farmland managers must increasingly provide habitat for displaced wildlife of open lands as agricultural conversion of natural habitats continues to rise (Tilman et al. 2001). Biodiversity conservation on agricultu ral lands is increasingly considered an important component of large-s cale conservation planning worldwid e (Green et al. 2005, Fischer et al. 2008). Farmlands are thought to provi de buffers around natural areas, softening the influences of more urbanized environments on natural ecosystem processes and wildlife populations by providing produc tive habitat for some species and at least marginal uses for other species that may depend on natural areas but ca n utilize more damaged ecosystems for some resources (Phillips 2002). In summary, our research s uggests that farmlands in general provide suboptimal but productive habitat for breeding bluebirds, at leas t in dry years (but see discussion of our studys limitations above). However, our re search is consistent with othe r findings that suggest that not all agricultural lands can provide buffers of equal value to wildlife (Hole et al. 2005). Eastern Bluebirds on conventional farms produced fewer hatc hlings than those on na tural control areas at the clutch-level of analysis (Tables 2-3 and 2-4), and they did not exhibit advantages over natural control areas in terms of incubation period (as was the case for those on reduced-impact farms; see above; Figure 2-4 and Table 2-3). Prior resear ch generally confirms that bird populations fare better on reduced-impact farms than on conv entional farms (Hole et al. 2005). We therefore recommend that reduced-impact farms receive pr iority over conventional farms in regard to conservation efforts geared toward the augmenta tion of avian biodiversity on farmlands or the incorporation of farmlands as bu ffer habitat for protected areas.

PAGE 33

Table 2-1. List of terms and definitions Term Definition Reduced-impact farms Non-orchard farms with a variety of different crops mixed row by row; Host a low ratio of crop to non-crop vegetation in the landscape; Lack powerful, synthetic pesticides Conventional farms Non-orchard monocultures (acres of field, and therefore several bluebird territories [Gowaty and Plis sner 1998] are planted with just one crop); Host a high ratio of crop to non-crop vegetation in the landscape; Frequently treated with insecticides and other pesticides Natural control areas Abandoned farm-fields/pastures with a mixture of native and non-native vegetation, within a matrix of long-leaf pine (Pinus palustris ) and mesic and hydric hardwood forest; An evolu tionarily historic habitat of the Eastern Bluebird (Gowaty and Plissner 1998) Clutch A set of eggs laid by a breeding pair of birds; Ea stern Bluebirds lay multiple clutches per breeding season Brood A clutch that produced at least one hatchling Hatchling A nestling hatched from an egg Fledgling A hatchling that presumably surv ived and left (i.e., fledged) its nest First-egg-date The date that the first egg of the first clutch of a pair was laid; Calculated under assumption that females lay one egg per day and that they do not lay eggs past 1100 hour s EST (Gowaty and Plissner 1998); An earlier first-egg-date may correla te with greater clutch production First-egg-day A translation of first-egg-date, for purposes of statistical analysis and presentation; Day 1 co rresponds to February 1st Incubation period The period between the time wh en the last egg of a clutch was laid and its eggs hatched (Gowaty and Plissner 1998); A shorter incubation periods may indicate higher quality of breeding habitat Interbrood lapse The period between the time th at the first clutch hatched and the first egg of the second clutch was laid ; A shorter interbrood lapse may indicate higher quality of breeding habitat BCI Nestling body-condition index; Calc ulated from the residual of the regression of ln(weight) on ln(tarsus length); Higher values correspond to nestlings with greater body condition BGI Nestling pre-fledging body-growth i ndex; calculated from the residual of the regression of ln(weight) on ln(wing cord) (Jakob et al. 1996); Higher values correspond to more developed nestlings that presumably have a better chance of survival Pair-ID Unique identification gi ven to a pair of bluebirds Brood-ID Unique identification given to one of potentially several broods of a pair of bluebirds 33

PAGE 34

Table 2-2. Description of statistical models Analysis Level Purpose Dependent Variables Fixed Effects Random and Repeated Effects Season-level Analyze reproductive success at the coarsest scale (i.e., over the entire breeding season) First-egg-date; Interbrood lapse; Total # clutches*, eggs*, hatchlings*, and fledglings* produced over the entire breeding season Land management (reducedimpact farms, conventional farms, natural control areas); first-egg-date also included in analyses of clutch and egg production None Clutch-level (All-treatments) Analyze clutch-byclutch reproductive success; Includes all treatment groups; Limited to first two clutches, as only one pair in the natural control group laid a third clutch # Eggs*, hatchlings*, and fledglings* produced; Hatching success*; Incubation period Land management (reducedimpact farms, conventional farms, natural control areas); clutch-order; landmanagement*clutch-order Pair-ID nested by Land Management Clutch-level (Farms-only) Analyze clutch-byclutch reproductive success; Includes clutches 1-3, but only but limited to reduced-impact and conventional farms Same as above Same as above, but land management groups restricted to reduced-impact farms and conventional farms Same as above Nestling-level (All-treatments) Analyze clutch-byclutch nestling BCI and BGI; Includes all treatment groups; Limited to first two clutches BCI and BGI of a randomly selected nestling from each brood; BGI recorded once at or above 14 days of age (pre-fledging stage); BCI measured several times throughout development Land management (reducedimpact farms, conventional farms, natural control areas); brood-order; landmanagement*brood-order; age-class, landmanagement*age-class also included in BCI analysis Pair-ID nested by Land Management for analyses of BCI and BGI; Nestling-ID nested by Pair-ID by Land Management also included for analysis of BCI Nestling-level (Farms-only) Analyze clutch-byclutch nestling BCI and BGI; Includes 1st-3rd clutches, but only but limited to reduced-impact and conventional farms Same as above Same as above, but land management groups restricted to reduced-impact farms and conventional farms Same as above Indicates a model that assumed a binomial, rath er than normal, distribution. Incubation period analyses replaced clutch-order with brood-order (definitions in Table 2). All-treatments analysis of incubation period did not include la nd-management*brood-order in the model, as the model would have been overparameterized. We did not analyze clutch-level fledging success because the dataset did not meet necessary convergence criteria. 34

PAGE 35

Table 2-3. Results Analysis Level Model ID Dependent Variable Independent Variable Num. DF Den. DF F Value pvalue Sig. posthoc results SL 1 First-eggday LM 2 43 5.90 0.0054 RIF,CF
PAGE 36

36 Table 2-3 Continued. Analysis Level Model ID Dependent Variable Independent Variable Num. DF Den. DF F Value pvalue Sig. posthoc results CL (FO) 15 Hatchlings LM*CO 2 81 0.81 0.4463 16 Hatching Success LM 1 26 1.66 0.2086 CO 2 81 3.32 0.0410 1<3 LM*CO 2 81 0.67 0.5159 17 Fledglings LM 1 27 2.91 0.0998 CO 2 76 5.65 0.0052 1<3 LM*CO 2 76 2.24 0.1130 18 Incubation Period LM 1 30 2.62 0.1163 BO 2 42 7.20 0.0020 2<1; 3<1 LM*BO 2 42 0.93 0.4036 NL (FO) 19 BCI LM 1 34.4 0.58 0.4512 BO 2 272 5.12 0.0066 2<1; 3<1 AC 5 263 0.96 0.4413 LM*BO 2 272 0.63 0.5351 LM*AC 5 263 0.82 0.5366 20 BGI LM 1 19.8 0.11 0.7487 BO 2 36 2.06 0.1426 LM*BO 2 36 0.30 0.7417 Only the details of significan t post-hoc comparisons are pres ented (alpha=0.05). SL=Seasonlevel, CL=clutch-level, NL=nestling-level; AT=All-treatments, FO=Farms-only; LM=land management; CO=clutch order; BO=brood-orde r; RIF=reduced-impact farm, CF=conventional farm, NC=natural control. Numbers in last column signify first, second, or third clutch or brood. Table 2-4. Effect of land management and clutch order on hatching success Land Management Clutch 1 Clutch 2 Clutch 3 Clutches 1 and 2 Total Control 0.78 0.93 0.86 0.86 Conventional 0.66 0.60 0.51 0.63 0.59 Reduced-Impact 0.80 0.66 0.64 0.73 0.70 Proportions represent number hatchlings divi ded by number of eggs produced per clutch.

PAGE 37

25 30 35 40 45 ControlConventionalReduced-Impact Land ManagementInterbrood Lapse (Days)50 55 60 65 70 75 ControlConventionalReduced-Impact Land ManagegmentFirst Egg Day Figure 2-1. Effect of land mana gement on first-egg-day and inte rbrood lapse. A first-egg-day value of corresponds to 1 February 2008. Farms, in general, hosted bluebirds that exhibited significantly lower first-egg-days and shorter interbrood lapses than natural control areas (alpha=0.05). Error bars indicate 1 SE. 0 2 4 6 8 10 12 14 16 18 20 354045505560657075808590 First Egg DayEggs Figure 2-2. Effect of first-egg-day on season-level pr oduction of eggs. A fi rst-egg-day value of corresponds to 1 February 2008. 37

PAGE 38

Figure 2-3. Effect of land manage ment on bluebird reproductive success. Y-axis indicates mean numbers of clutches, eggs, hatchlings or fledglings per nest. Panels indicate A) season-level reproductive success, B) first-clutch reproductive success, C) secondclutch reproductive success, and D) thirdclutch reproductive success. Error bars indicate 1 SE. C0 1 2 3 4 5 6 ControlConventionalReduced-Impact D0 1 2 3 4 5 ConventionalReduced-Impact A 0 5 10 15 ControlConventionalReduced-Impact ClutchesB 0 1 2 3 4 5 6 ControlConventionalReduced-Impact EggsEggs Hatchlings Hatchlings Fledglings Fledglings 38

PAGE 39

12 12.5 13 13.5 14 14.5 15 15.5 1st Brood 2nd Brood 3rd BroodIncubation Period (Days) Control Conventional Reduced-Impact Figure 2-4. Effect of land management and brood-order on incubation period. Bluebirds on reduced-impact farms incubated for signifi cantly less time than those in natural control areas. Second and third broods took significantly less time to incubate than first broods (alpha=0.05). E rror bars indicate 1 SE. -0.03 -0.02 -0.01 0 0.01 0.02 0.03 1st 2nd 3rd BroodBody Condition Inde x Figure 2-5. Effect of brood or der on nestling body condition inde x (BCI). First-brood BCI was significantly higher than sec ondor third-brood BCI (alpha =0.05). This analysis only included nestlings from farms. Error bars indicate 1 SE. 39

PAGE 40

CHAPTER 3 REDUCED-IMPACT FARMING, PREY BIOM ASS, AND THE REPRODUCTIVE SUCCESS OF EASTERN BLUEBIRDS ( SIALIA SIALIS ) Introduction Wildlife-Friendly Farming Wildlife-friendly farming has recently gained the attention of ecologists, conservationists, and policy-makers (Green et al. 2005, Fischer et al. 2008, Scherr and McNeely 2008). From systems producing coffee to broccoli, the maintenance and even enhancement of native biodiversity on farmlands is under study (G reenberg et al. 2000, Daily et al. 2001, Mols and Visser 2002, Phillips 2002, Hooks et al. 2003, Jones et al. 2005, Borkhataria et al. 2006, Jones and Sieving 2006, Sekercio glu 2007). Simultaneously, agricultural policie s around the world are changing to reflect increasing awarenes s of the needs for biodi versity conservation on farmlands (Fischer et al. 2005, Wild Farm Allian ce 2005), potential benefits that native species provide in some systems (e .g., pest control; Greenberg et al. 2000, Mols and Visser 2002, Phillips 2002, Hooks et al. 2003, Jones et al. 200 5, Borkhataria et al. 2006), and consumer desires to buy foods produced using environmen tally sound practices (Grankvist & Beal 2001). In general, fostering appropriate (non-pest) native species on fa rmlands appears to have few or no negative economic or ecological effects on fo od production (Hole et al. 2005, Scherr and McNeely 2008), and landscapes dominated by ecoagriculture may even benefit the public (from aesthetics and ecological services to recreati on; Scherr and McNeely 2008). However, while attracting wildlife to farms is not difficult, especially in landscapes supporting significant amounts of native habitat (Jones and Sievi ng 2006), it is important to determine if organic and other wildlife-friendl y farms provide suitable breeding habitat for wildlife. Even agriculture-dominated lands with interspersed remnants of native habitat (i.e., soft matrix Green et al. 2005) may not suppor t viable populations in dependent of native, 40

PAGE 41

source populations (Sekercioglu et al. 2007). Therefore, as sessments of farms from a conservation perspective should make a distinct ion between wildlife use versus sustainable production of wildlife populations and communities on farmlands. Only in this way can ecology inform natural resource policy and land management decisions that best support wildlife-friendly farming or other conservation-minded, multiple-use alternatives (e.g., land-sparing; Fischer et al. 2008). Effects of Food Resources on Avian Reproduction For example, no research has addressed the quest ion that if we attract birds to farms, do these birds eat well enough to support their health survival, and reproducti on? Quantity of food available in early spring is a common proximate cue for breed ing birds (Martin 1987, Nooker et al. 2005, Pimentel and Nilsson 2007). Reduced-imp act farms in North-central Florida typically grow crops continuously through fall, winter, and spring, and part of summer (but not in JulySeptember; JJD personal observation ). The presence of green vege tation (i.e., crops), subsidized by irrigation and fertilizer on farms, may support arthropod prey populations that may not otherwise exist during the dry season (NOAA 2008), there by allowing bluebirds on farms to begin reproduction earlier th an those in natural areas. The quality, quantity, and stability of food resources have been shown to affect reproductive success in a variety of bird taxa (Korpimaki 1992, Phillips et al. 1996, Valkama et al. 2002, Davis et al. 2005, Lindstrom et al. 2005). We observed in previous research that farmland pest insect populations appeared to vary dramatically, as farm-fields shifted between being planted or harvested, or bei ng tilled versus left fallow (JJD personal observation ; see also Nebel 1993). Although long-term prey biomass may be greater on farms than in natural areas (due to resource subsidies and higher peak in sect population sizes), th e instability of food resources may also be greater on farms than natu ral open lands. When insect populations crash 41

PAGE 42

because of crop harvest, mowing, or tilling, this may decrease reproductive success as parents may have more difficulty feeding themselves or their nestlings at key (a nd unpredictable) times during the reproductive cycle (Korpimaki 1992, Phillips et al. 1996, Valkama et al. 2002, Davis et al. 2005, Lindstrom et al. 2005 ). Truly wildlife-friendly farms should host stable food resources of adequate quantity and quality to su stain viable wildlife populations. Nevertheless, researchers have yet to comp are the quality, quantity, or st ability of food resources on supposedly wildlife-friendly farms in relation to natural open lands. Avian Reproduction on Wildlife-friendly Farmlands In a previous study conducted in 2007 (Chapter 2), we compared the reproductive success of Eastern Bluebirds (Sialia sialis ) nesting on natural control areas, conventionally-managed farms, and reduced-impact (organic and other low-input systems) fa rms in North-central Florida. Reduced-impact farms in 2007 could generally be de scribed as wildlife-friendly" from a habitat perspective; they were planted with a variety of crops in a pa tchwork of fallow fields, with interspersed tree islands, windbreaks, hedgerows, a nd nearby forest patches. Furthermore, many reduced-impact farms were managed under the requirements for USDA-organic certification (Green et al. 2005, Fischer 2008). The most important result of our research wa s that bluebirds began nesting much earlier on both types of farms and therefore raised more clutches on farms than in natural areas (3 on average versus 2), yet bluebirds on farms and natural areas produced similar numbers of nestlings over the breeding seas on. Greater within-season breedi ng effort can decrease lifetime reproduction and adult survival (Slagsvold 1984, Smith et al. 1987, Tinbergen 1987, Gustafsson et al. 1994, Richner et al. 1995, Deerenberg et al. 1997, Nilsson and Svensson 1996, Raberg et al. 1998). Our previous findings therefore suggest that even reduced-impact farms may not be as wildlife-friendly as expected (G reen et al. 2005, Hole et al. 2 005, Fischer et al. 2008). Food 42

PAGE 43

resources of lower quality, quantity, or stabil ity may have caused this lower reproductive efficiency on farms. In order to fully addre ss the goal of our research program to explore wildlife-friendly farming from the conservation perspective addressing whether such farms provide high quality habitat that supports reproduction adequate to support viable populations we conducted a follow-up study to address whether differences in food resources underlie differences in bluebird reproductive success a nd breeding behavior. Given that conventional farm management involves high inputs of pesticides and fertilizers and is not considered as wildlife-friendly as organic farm s (Hole et al. 2005), we encour aged bluebird nesting only on natural control areas and organic (or organically managed) farms. Research Design In 2007, we established a causal link between la nd management and various measures of reproductive timing and success (dashed arrow, Figur e 3-1). Here we test the hypotheses that food resources affect bluebird reproduction (solid arro w, Figure 3-1) and that land management affects food resources (solid arrow, Figure 3-1), thereby linking land management to reproduction through the mechanism of food-resource effects. We c ontrolled for the effects of nest predation in our researc h, enabling us to focus on the e ffects of prey availability on reproduction (see Methods). We recognize two co mponents of bluebird prey availability: biomass of known prey present in foraging microha bitat used by bluebirds, and the stability of said prey biomass. Using a comparative ob servational design, we monitored bluebird reproduction and sampled arthropod populations on reduced-impact vegetable farms and natural control areas in North-central Fl orida. We monitore d first-egg-date and number of clutches produced per pair over the season, but we limited our analyses of reprod uctive success to first clutches. 43

PAGE 44

We addressed the following specific hypothese s and predictions. H1: Food resources (measured in terms of prey biomass and stabili ty) affect first-egg-date, clutch production, and reproductive success (i.e., first-clutch egg and hatchling production). Predictions for H1 include: a) higher prey biomass and stability just prior to the onset of breeding will correlate with earlier first-egg-dates, b) greater prey biomass thr ough the season will correlate with higher clutch production and reproductive succe ss, and c) less variation in prey biomass through the season will correlate with higher clutch production a nd reproductive success. H2: Land management affects food resources (prey biomass and stability ). Predictions for H2 include: a) farms will host higher prey biomass but b) lower prey stabi lity than natural control areas. Since these hypotheses were proposed to explai n the results of Chapter 2, we assumed for this study that patterns of reproductive success in relation to land management observed in 2007 (Chapter 2) would be similar in 2008. In 2007, farmland bl uebirds began breeding earlier and produced more clutches than those in na tural control areas, and first-clutch egg and hatchling production were similar on farms and natural areas. We monitored bluebird reproductive behavior and output in order to verify whether these patterns persisted in 2008. Methods Study Species, Study Sites, and Nest-Box Placement The Eastern Bluebird is a charismatic, pr imarily insectivorous, multiple-brooded, groundforaging, secondary cavity-nester of open lands (Gowaty & Plissner 1998). We conducted our research on three USDA-certified organic farms and one organically managed (i.e., in process of certification) farm in Alachua C ounty, Florida, and six natural c ontrol areas within the >3760 ha Ordway-Swisher Biological Station in adjacent Pu tnam County. All farms exhibited the typical heterogeneous structure of wildlife-friendly farms (Green et al. 2005, Jones et al. 2005, Jones and Sieving 2006, Fischer 2008). Natural control areas consisted of abandoned pasture in the 44

PAGE 45

process of natural restoration, with a mixture of native and non-na tive grasses and shrubs, within a landscape of l ong-leaf pine ( Pinus palustris ) and both mesic and xeric hardwood forests (Gowaty and Plissner 1998). We monitored 31 nest-boxes on 4 reduced-impact farms and 32 boxes in 6 natural control sites, beginning in mid-February. No nest -box was placed less than 70 m from its nearest neighbor. Nest-boxes on farms were placed within 5 meters of the edges of farm-fields (barren, fallow, or with active crop growth ), and within at least 200 m of fields with actively growing crops at some point in the seas on. Nest-boxes in all treatments were within 50 m of protective cover and perching substrates used by bluebirds (e.g., hedgerows, tree islands, windbreaks, forest). In order to control for predation, we mounted nest-boxes on narrow, metal poles (approximately 1.5 m high) and kept the poles greased (USDA Natural Resources Conservation Service 1999). Prey Surveys We sampled arthropod populations on an appr oximately weekly basis between February 17th (12 days before the first clutch of the s eason was laid) and June 1st. We conducted two types of transects, both 20 m long: grasshopper-walk (GW) and walk-brush (WB) surveys. The purpose of GW surveys was to count large mobile arthropods (e.g., Or thoptera, Lepidoptera, Odonata) that move dramatically when approached and therefore are easy to see. GW transects were located in microhabitat with the tallest he rbaceous vegetation availa ble during a given visit to each of the areas. On farms, we did not conduct GW surveys in actively growing crops, but rather in field edges or fallow fields with weeds. We conduc ted GW surveys by walking at 1 pace per second for 10 m while recording all arth ropods that moved or were readily visible within approximately 1 m on either side of the observer, avoiding double-counting. 45

PAGE 46

The purpose of WB surveys was to target smaller, ground-dwelling arthropods, and those animals inhabiting low, actively growing herbac eous vegetation, includin g crops. In natural control areas, WB surveys were conducted in herbaceous vegetation, and on farms they were conducted between crop rows (principally leafy vegetables such as kale, cabbage, broccoli, collared greens, etc.; see Jones et al. 2005). We conducted the first 10 m of WB surveys in the same manner as GW surveys. During the second 10 m, we bent low, brushed vegetation with our hands, and looked under leaves and plants, in the middle of the vegetation layer, and on top of vegetation, within 1 m to either side of the tr ansect line. Time to complete brushing varied depending on arthropod abundance (our aim was to conduct a thorough sear ch), as the time it took to count and classify arthropods and reco rd data increased as we encountered more arthropods. We developed these sampling methods based on Ga rdiner et al. (2005) in order to sample prey that were frequently taken from foraging microhabitats commonly used by bluebirds nesting on the study sites (JJD unpublishe d data). Adult Orthoptera and Lepidoptera larvae were the principal prey items identified in previous obs ervations (though many sma ller prey could not be identified), and bluebirds frequently foraged in crops, fallow fields, and field edges within 100m of the nesting site, but also flew further away (to unobservable locations off site; JJD unpublished data). Previous research confirms these patterns (Gowaty and Plissner 1998). By conducting WB transects between crop rows and GW surveys in fallow vegetation surrounding farm fields (and in the most similar mi crohabitat available in natural control areas) we assessed representative food resources av ailable to bluebirds on both types of land management. After bluebirds began nesting, we conducted prey surveys within 100 m of nests in each site in appropriate foraging habitats. To maintain independence of samples, observers 46

PAGE 47

avoided using any transect more than once. We selected transect locations subjectively on each visit to sites, by looking for t hose areas with vegetation that was most dense and actively growing (greenest), assuming that such vegetation would attract the kind of herbivorous prey that bluebirds target. We conducted at least two (up to 8) of each type of transect (GW and WB) at each visit to a site the number of transects per site was proportional to the number of boxes clustered at each site (box number varied from 3 to 10 per site). We only recorded arthropods that were grea ter than 0.5 cm in length. We classified arthropods into 6 size categories (0.5-1 cm, 1-2 cm 2-3 cm, 4-5 cm, 5-6 cm, and 6 or more cm). Five different observers conducte d arthropod surveys. We monito red cloud cover, temperature, and wind speed during sample periods to insure some degree of standardization of conditions. We conducted surveys between 0800 and 1630 hours, EST. We did not conduct surveys during rain events or when winds reached more than 15 km/hr. We conducted surveys in exposed (unshaded) microhabitats with full insulation and avoided the coldest periods during the day (early morning). Prey Indices We summarized prey data for three distinct time periods for use in statistical analyses. Pre-breeding prey indices repr esented food resources th at were available ju st before and during nest initiation; data were used from all transe cts sampled between February 17th (more than one week before the earliest first-egg-date) and March 13th (the mean observed first-egg-date on farms, the treatment with the ea rlier mean first-egg-date). F irst-clutch prey indices were calculated to represent the food available to pairs during th eir first clutch of the 2008 season. Specifically, we based first-clutch prey indice s on those transects sampled between the two weeks before and the two weeks af ter the average first-egg-date at each site (i.e., different time periods were used for different sites). Finall y, Season-long prey indices were calculated using 47

PAGE 48

data from the entire arthropod sampling period (i .e., mid-February to early June) spanning both first and second brood attempts across all study sites. For these three time periods, two types of i ndices were calculated for both GW and WB data. For each 20m survey, we calculated a prey biomass index, one for each type of sampling method (GW or WB), equal to the absolute number of prey items encountered during a survey multiplied by the mean prey-size. We then averaged these data on a site-by-site basis for each time period (pre-breeding, fi rst-clutch, or season-long) and both survey type (GW or WB). In addition, we quantified prey biomass stability usi ng the coefficients of variation across transect during each of these time periods and for both survey types. Monitoring Bluebird Reproduction We monitored the nesting activity of Eastern Bl uebirds, at different levels of intensity, during the entire breeding season of 2008 (February-August). We recorded nest-construction status, number of eggs, and number of hatchlings at each visit to a nest-box. Before bluebirds laid their first clutches, we monitored nest-boxe s once or twice per week in order to estimate first-egg-date within two days accuracy (over 85% we re determined to the exact date; assuming bluebirds lay one egg every 24 hours and do not la y past 1100 hours; Gowaty & Plissner 1998). We define first-egg-date as the da y that the first egg of the first clutch of a pair was laid. Firstegg-date was translated into first-egg-day, with Day 1 equal to February 1st (e.g., a first-egg-day value of 27 would be equal to February 27th and a value of 29 would equal March 1st). After the majority of first clutches were laid, we visited sites once per week, and after early June (when first clutches were finish ing), we reduced visitation rates to between 10 15 days between visits, with some longer periods (up to 3 weeks at the end of th e season). Visits were more frequent early in the breeding season to establis h precise estimates of first-egg-dates and food availability in the early breeding season (for testing H1 and verifying whether reproductive 48

PAGE 49

success in the first clutch reflected 2007 patterns w ith respect to farms versus natural areas). By continuing to visit sites throughout the breeding season (though less often) we could assess longterm (season-long) prey biomass and variabilit y, and determine clutch produciton. The typical Eastern Bluebird nesting cycle lasts 28 days (G owaty and Plissner 1998), so we visited nests often enough to be able to calculate the total num ber of clutches and mean number of nestlings produced per pair over the br eeding season. Poles that secu red the nest-boxes above ground were continually greased to prev ent predation (as in Ch apter 2). We identified predation events by marks left by predators on boxes, nests, and grease. We accordingly removed predated nests from analyses. Statistical Analysis In testing statistical hypotheses, we used sites as replicates. Based on previous observations (JJD), we assumed different pair s nesting within the same site foraged in unpredictable, often overlapping terr itories. Furthermore, we c onducted prey surveys at various locations spread across each si te, not around each nest-box. That is, we did not conduct prey surveys around particular breeding pairs (and we could not do so before breeding began, anyway). We therefore analyzed data on a site-by-site (not pair-b y-pair) basis. This limited our sample size (n=4 farms and 6 natural control areas ), so we used nonparametric analyses to avoid making assumptions about underlying distributions th at we were unable to identify. We used the Spearman Correlation Index to test H1, and th e Mann-Whitney U Test to test both H2 and predictions concerning assumed patterns of reproduc tive success (see first fi ve columns in Table 3-1 for details of analytical methods; data analyzed in SPSS 16.0). 49

PAGE 50

Results Prey Availability Pre-breeding GW prey biomass inversely corr elated with first-egg-date (Spearman R=0.770; p=0.009; Figure 3-2; Table 3-1), but pre-breeding WB prey biom ass did not. None of the other GW or WB prey biomass indices was correlat ed with first-egg-date (Table 3-1). No prey biomass indices were correlated with seasonlong clutch production or first-clutch egg production (Table 3-1). Fi rst-clutch GW prey biomass, WB prey biomass, and GW instability were unrelated to first-clutch hatchling production (Table 3-1), but first-clutch WB instability was inversely correlated with first-clutch hatchling production (Spearman R=-0.654; p= 0.040; Figure 3-3; Table 3-1). Season-long GW and WB prey bi omass were higher and more unstable on farms than in natural control areas ( p<0.02; Figure 3-4; Table 3-1) Pre-breeding and firstclutch prey indices did not vary signifi cantly between farms and natural areas. Land Management and Bl uebird Reproduction Confirming results obtained in the previous year (Chapter 2), fa rmland bluebirds began breeding earlier than those in natural control areas ( p=0.038; Figure 3-2; Ta ble 3-1), but land management was not clearly related to clutch or first-clutch egg production (Figure 3-3; Table 31). In contrast to 2007 patterns, farmland bluebi rds produced a similar number of clutches but significantly fewer first-clutch hatchlings than those in natural control areas ( p=0.010; Figure 35; Table 3-1). Confirming 2007 patterns, bluebi rds that began breeding earlier produced more clutches ( p= 0.027; Figure 3-6; Table 3-1). Discussion Prey Availability as a Mechanis m for Earlier First-Egg-Dates The hypothesis that prey availability may influence first-egg-date was confirmed. Bluebirds in habitat w ith higher pre-breeding GW biomass began breeding earlier. As in 2007, 50

PAGE 51

bluebirds on farms in 2008 exhibited earlier first-e gg-dates than those in na tural control areas. This finding is in line with other work showi ng that the abundance of food resources determines the onset of avian reproduction (Martin 1987, Nooker et al. 2005, Pimentel and Nilsson 2007) and provides a reasonable mechanism to explain earlier first-egg-dates on farms (Figure 3-2; Table 3-1). Even though we were unable to detect a difference in prey biomass between farms and natural areas during the pr e-breeding period, farms did support greater prey biomass over the course of the breeding season (Feb to June; Figu re 3-4; Table 3-1), prov iding partial support for predictions under H2. It is likely that ability to detect pre-br eeding prey differences between farms and natural areas was limited because many fe wer surveys went into the calculation of prebreeding indices (less than 10 surveys per site) th an into long-term indices. In addition, small sample sizes may have also limited power (n=6 na tural control areas and 4 farms). Given that previous research shows that earl y breeding in birds is related to early food availability (Martin 1987, Nooker et al. 2005, Pimentel and Nilsson 2007), and that farms in our study produced more prey biomass over the season than natural areas, we suggest that land management likely influenced first-egg-date in our study via differences in pre-bree ding prey biomass (Figures 3-2 and 3-4). This hypothesis should be re-tested with a more rigorous sampling regime by sampling more farms at a higher rate during the pre-breeding period. Prey Biomass Instability and Hatchling Production Prey biomass and instability indices did not co rrelate with either clutch production or firstclutch egg production. However, prey instability was linked to first-clutch hatchling production and was significantly higher on reduced-impact fa rms where significantly fewer hatchlings were produced (Figures 3-3 and 3-4; Table 3-1). Bluebi rds in sites with less stable WB prey biomass produced fewer hatchlings (Figure 3-3; Table 31). Farms exhibited significantly higher WB prey instability over the course of the season than natural control areas (and first-clutch WB prey 51

PAGE 52

instability tended to be higher on farms; Figure 3-4; Table 3-1). Because fi rst-clutch prey indices were calculated based on fewer sampling periods than season-long indices (as for pre-breeding indices, see above), the pow er of statistical tests relating firstclutch prey availability to firstclutch reproduction was likely to be limited in this study. Given the marked season-long differences in prey biomass stability on farms, however, we conclude that land management could very likely influence hatchling production through the m echanism of prey instability (Figures 3-3 and 3-4). Unstable food resources affect reproductive success for a variety of birds (Korpimaki 1992, Phillips et al. 1996, Valkama et al. 2002, Davis et al. 2005, Lindstrom et al. 2005). Specifically, our data s how that first-clutch reproducti ve output was lower not because hatchlings died, but because eggs did not hatch (i.e., we observed dead eggs in nests after viable eggs hatched). Perhaps prey instability caused female bluebirds on farms to spend more time off of the nest in search of prey, ther eby decreasing their time spent incubating eggs. Alternatively, prey instability may have prevente d females from gaining the proper nutrition to produce viable eggs (Martin 1987). Our detection of prey biomass instability on farms could be explained by prey population cycles generated by typical farming dynamics. Water and fertilizer subsidies can create artificially high arthropod populations, and harvest and field fallowing activities can cause abrupt drops in arthropod biomass (Nebel et al. 1993). Moreove r, we may have detected higher overall mean prey biomass on farms simply because of the artificially high population explosions on farms that unsubsidized natural areas did not experience. Without more detailed measures of where individual bluebird pairs foraged during specific portions of their nesting cycle, and the availability of prey in fora ging sites, we cannot explain mo re about how or why farmland bluebirds suffered lower hatchability in this st udy. However, the fact that farms had greater 52

PAGE 53

overall prey biomass suggests that bluebirds are exceptionally sensit ive to fluctuations in spatiotemporal distribution of their pr ey and that improving farmlands for wildlife conservation may require improvements in the stability of f ood resources (Korpimaki 1992, Phillips et al. 1996, Valkama et al. 2002, Lindstrom et al. 2005). First-egg-date and Season-level Clutch Production Though farmland bluebirds began breeding earlier than those in natu ral control areas, clutch production over the season was not different between farms and natural areas (Figure 3-3; Table 3-1). This contrasts with 2007 result s from the same study system, when farmland bluebirds nested earlier and produ ced more clutches than bluebird s on natural areas, resulting in a significantly greater overall re productive effort on the part of farmland birds (Chapter 2). In light of current results, the cont rast in patterns of relative produc tion of clutches and reproductive effort between years appears most closel y linked to first-egg date (Figure 3-6). Based on 2007 data alone, we concluded that higher clutch production was probably coupled to farming. However, farmland bluebi rds in 2008 did not produce more clutches than their natural counterparts (Figure 3-6; Table 3-1) This may have resulted because bluebirds on natural areas began breeding mu ch earlier in 2008 than 2007 (approximately two weeks earlier; Figure 3-5). Since the difference between cl utch production on farms and natural areas disappeared in 2008, it may be that the extra tw o weeks of early breed ing was enough to allow bluebirds in natural control ar eas to catch up to farmland bluebirds in terms of clutch production. Indeed, the mean firs t-egg-date of bluebirds in natural control areas in 2008 corresponded to the mean first-egg-date of bluebirds on farms in 2007 (Figure 3-5). Furthermore, land management was correlated w ith prey biomass and stability (Figure 3-4; Table 3-1) but not to clutch pr oduction, and prey biomass and st ability did not correlate with season-long clutch production. On ly first-egg-date was related to season-long clutch production 53

PAGE 54

(in both 2007 and 2008). Finally, previous resear ch on Eastern Bluebirds across North America confirms this finding in demonstrating that as la titude increases, firstegg-date increases and clutch production consequently decr eases (Gowaty and Plissner 1998). The difference in first-egg-date between 2007 an d 2008 could be related to rainfall levels. Substantially more rain fell in the study region in 2008 than in 2007 and probably influenced the earlier onset of breeding (Table A-3; FAWN 2008). Rainfall levels in both years (2007 and 2008) fell outside the 95% confidence interval for rainfall levels in the past eight years (with 2008 falling above and 2007 below the upper and lo wer bounds; Table A-3). In other words, rainfall in the months when bluebirds began br eeding (February-April) was more than twice as high in 2008 than 2007 (Table A-3). Higher rainfa ll in the early months of breeding may have stimulated the growth of green vegetation, wh ich consequently may have sparked earlier increases in pre-breeding prey biomass (which we have shown correlates with earlier first-eggdates, which in turn correlate with higher cl utch production; Nooker et al. 2005, Pimentel and Nilsson 2007). Indications for Lower Reproductive Success on Farms Results of this study reveal another contrast with our 2007 findings. In 2007, farmland birds bred earlier, ra ised more clutches but achieved equal numbers of fledged young per pair, leading us to conclude that while reproductive efficiency was lower on farms; net reproductive success in the same season was equal. In 2008, bluebirds in natural c ontrol areas produced similar numbers of clutches as farmland bluebird s (Figure 3-3; Table 3-1), presumably because farmland bluebirds lost the relati ve advantage of being able to nest just enough earlier to lay more clutches than control bird s. It is also possible that ov erall food abundance on natural areas in the drier year (2007) was low enough to discou rage late-season clutches, limiting them to only two clutches for the season (Chapter 2). 54

PAGE 55

We did not conduct monitoring activities in tensely enough to describe the reproductive success of second and third clutches in this study (see Methods). However, it is possible that the reproductive success of later clutches on farm s was much poorer in 2008 than 2007, and than bluebirds in natural control area s in 2008. Second and third clutches met worse fates than first clutches on farms in 2007 (Chapter 2). One c ould reasonably extrapolate this pattern to 2008 bluebirds, as life-history theory expects decreased reproductive success in successive clutches, and this pattern is frequently observed in avian species (Slagsvol d 1984, Smith et al. 1987, Tinbergen 1987, Gustafsson et al. 1994, Richner et al. 1995, Deerenberg et al. 1997, Nilsson and Svensson 1996, Raberg et al. 1998). Neverthele ss, we cannot conclude anything definitively about the season-level reproductive success of bl uebirds in 2008 without actual data on second and third clutches. It appears that farms serve as suboptimal but productive habitat for breeding bluebirds during especially dry years like 2007 (Chapter 2; Table A3; FAWN 2008), as farmland bluebirds were able to match the net reproductiv e success of bluebirds in natural control areas (albeit they exerted more effort; Chapter 2). Du ring years with especially high rainfall, however, the quality of farmlands as breeding habitat for bl uebirds dropped relative to natural areas. In years with high rainfall levels (like 2008), birds on natural areas appeared to be able to lay as many clutches as farmland birds and exhibit higher reproductive success (Figure 3-3). Our data suggested that arthropod prey reso urces may be a crucial factor in determining this pattern, as high biomass was correlated with ea rlier first-egg-dates (which in turn determined the number of clutches produced per season) and high instability w ith reduced hatchling production (Figure 3-2 and 3-3). Bluebirds on natural areas were expos ed to lower prey biomass (by both GW and WB indices) but still did better than farmland birds that had more biomass available but with much 55

PAGE 56

56 less predictability. Previous research further co rroborates that volatile food resources lead to lower reproductive success (Korpimaki 1992, Phillips et al. 1996, Valkama et al. 2002, Lindstrom et al. 2005). However, we would make these conclusions with stronger inference had we conducted this research on more farms and natural sites over a broader spatial and temporal extent: We monitored bluebirds on few farms and natural co ntrol areas within a limited geographic domain (North-central Florida), our natural control areas may ha ve exhibited some spatial autocorrelation (as they were spread throughout one large reserve), and our research occurred over just two breeding seasons. Given that the va st majority of natural habitat development is from natural lands to agriculture (Tilman et al. 2001), and that habitat development is the primary threat to wildlife conservation (Van Dyke 2003), conservation biologists are increasingly hoping that farmlands may serve as productive habitat for songbirds and other wildlife species adapted to open lands (Green et al. 2005, Fischer et al. 2008). However, indications of low avian reproductive success in our study system and similar systems (Sekercioglu et al. 2007) suggest that more empirical research into the effects of supposedly wildlife-friendly farms on wildlife reproductiv e success would be prudent before we promote them as conservation lands.

PAGE 57

Table 3-1. Results Model ID Hypothesis/Assumption Addressed Analysis Type Dependent Variable Independent Variable Test Statistic pvalue Sig. posthoc results 1 H1 Spearman First Egg Day Pre-breeding GW Prey Biomass -0.479 0.009 2 H1 Spearman Pre-breeding WB Prey Biomass -0.515 0.128 3 H1 Spearman Clutch Production Long-term GW Prey Biomass 0.291 0.415 4 H1 Spearman Long-term WB Prey Biomass 0.550 0.100 5 H1 Spearman Long-term GW Prey Instability 0.291 0.415 6 H1 Spearman Long-term WB Prey Instability 0.045 0.901 7 H1 Spearman First-clutch Egg Production First-clutch GW Prey Biomass -0.359 0.309 8 H1 Spearman First-clutch WB Prey Biomass -0.334 0.345 9 H1 Spearman First-clutch GW Prey Instability -0.486 0.154 57

PAGE 58

Table 3-1 Continued Model ID Hypothesis/Assumption Addressed Analysis Type Dependent Variable Independent Variable Test Statistic p-value Sig. posthoc results 10 H1 Spearman First-clutch WB Prey Instability -0.164 0.650 11 H1 Spearman First-clutch Hatchling Production First-clutch GW Prey Biomass 0.232 0.518 12 H1 Spearman First-clutch WB Prey Biomass 0.110 0.762 13 H1 Spearman First-clutch GW Prey Instability -0.110 0.762 14 H1 Spearman First-clutch WB Prey Instability -0.654 0.040 15 H2 Mann-Whitney U Pre-breeding GW Prey Biomass Land Management -1.066 0.352 16 H2 Mann-Whitney U Pre-breeding WB Prey Biomass Land Management -1.066 0.352 17 H2 Mann-Whitney U Long-term GW Prey Biomass Land Management -2.345 0.019 RIF>NC 18 H2 Mann-Whitney U Long-term WB Prey Biomass Land Management -2.345 0.019 RIF>NC 19 H2 Mann-Whitney U Long-term GW Prey Instability Land Management -2.345 0.019 RIF>NC 58

PAGE 59

59Table 3-1 Continued Model ID Hypothesis/Assumption Addressed Analysis Type Dependent Variable Independent Variable Test Statistic p-value Sig. posthoc results 20 H2 Mann-Whitney U Long-term WB Prey Instability Land Management -2.558 0.010 RIF>NC 21 H2 Mann-Whitney U First-clutch GW Prey Biomass Land Management -0.426 0.762 22 H2 Mann-Whitney U First-clutch WB Prey Biomass Land Management 0.000 1.000 23 H2 Mann-Whitney U First-clutch GW Prey Instability Land Management -1.066 0.352 24 H2 Mann-Whitney U First-clutch WB Prey Instability Land Management -1.706 0.114 25 A1 Mann-Whitney U First Egg Day Land Management -2.132 0.038 RIF
PAGE 60

Land management Reproductive timing, success, and efficiency Timing, quantity, and stability of prey biomass Figure 3-1. Design logic for Chapter 3. Using a compara tive-observation study design, we tested the hypotheses that prey ava ilability affects bluebird reproduction and that land management affects prey av ailability (solid arrows). We also tested the assumption that land management affects reproductive success and behavior (dashed arrows), based on resu lts of a previous study (Chapter 2). B 30 35 40 45 50 55 60 65 70 Control Farms Land ManagementA0 10 20 30 40 50 60 70 80 90 0510152025 Pre-breeding GW Prey BiomassFirst-Egg-Day Figure 3-2. Effect of land management and pre-breeding GW prey biomass on first-eggday. A) Effects of land management. B) Effects of pre-breeding GW prey biomass. Error bars represent 1 SE. 60

PAGE 61

A 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 123456 First-Clutch WB Prey Instability (CV)First-clutch Hatchlings B 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Control Farms Land Management Figure 3-3. Effect of first-clutch WB prey instability (CV) and land management on first clutch hatchling production. A) Effects of first-clutch WB prey instability. B) Effects of land management. Error bars represent 1 SE. 61

PAGE 62

Figure 3-4. Effect of land management on long-te rm prey biomass, long-term prey instability (CV), and first-clutch WB prey instability. A) Effects on long-term prey biomass. B) Effects on long-term prey instability. C) E ffects on first-clutch WB prey instability. GW denotes grasshopper walk surveys, a nd WB denotes walk-brush surveys. Error bars represent 1 SE. A 0 5 10 15 20 25 30 Control Farms Land ManagementLong-term Prey BiomassB0 1 2 3 4 5 6 Control Farms Land ManagementLong-term Prey Instability (CV) GW WB C 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Control Farms Land ManagementFirst-clutch WB Prey Instability 62

PAGE 63

2007 B 0 0.5 1 1.5 2 2.5 3 3.5 Control Farms Land ManagementClutchesA 30 35 40 45 50 55 60 65 70 75 Control Farms Land ManagementFirst Egg Day2008 C0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Control Farms Land ManagementHatchlings Figure 3-5. Effect of land management on first-egg-day, clutch production, and hatchling production, compared by year. A) Effects on first-egg-day. B) Effects on clutch production. C) Effects on hatchling production. Erro r bars represent 1 SE. 63

PAGE 64

0 0.5 1 1.5 2 2.5 3 3.5 3540455055606570758085 First-Egg-DayClutches Figure 3-6. Effect of firstegg-day on clutch production 64

PAGE 65

CHAPTER 4 ARE WILDLIFE-FRIENDLY FARMS REALLY WILDLIFE-FRIENDLY? In targeting farmland habitat for biodivers ity conservation, policy-makers and natural resource management professionals must c hoose between two distinct types of farm management, land-sparing or wildlife-friendly operations. Land-sparing operations entail uniformly planted agricultural lands (i.e., monocu ltures) that are managed to increase yields through high-intensity inputs of fertilizer and pe sticide, while maintaining separate natural reserves for biodiversity conserva tion. Wildlife-friendly operat ions integrate conservation and farming within more diverse landscapes over a larger area, without necessarily protecting separate reserves (Fischer et al. 2008). Conservation biologists have recently expressed support for the latter method of land management (e.g., Green et al. 2005, Fischer et al. 2008). However, ecologists are only beginning to examine the potential of farmlands as productive habitat for breeding birds and other wildlife, and results remain inconclusive (e .g., Sekercioglu et al. 2007). Our research also indicates that reduced-impact farms (which could just as well be considered wildlife-friendly) do not necessarily provide ideal habitat for farm land wildlife, in contrast to popular notions (Green et al. 2005, Hole et al. 2005, Fischer et al. 2008). Bluebirds on reduced-impact farms produced many more nestlings in poor body condition and reproduced with much less efficiency (i.e., pairs laid more clutches and raised more broods but produced the same number of young) than bluebirds in natural control areas in 2007. Di fferences were also distinct in the subsequent year (2008); bluebirds produced a pproximately twice as many firstclutch hatchlings in natural control areas as on farms (a pattern that, if persistent throughout th e entire breeding season, would result in lower production of young on farms). 65

PAGE 66

While data presented here may seem to indi cate that farms did not provide as excellent breeding habitat as natural areas, farmland blue birds still produced s ubstantial numbers of offspring. Bluebirds on farms produced more than enough young to replace themselves in both 2007 and 2008 (assuming that most offspring survived after fledging), and th ey exhibited similar net reproductive success as bluebirds in natura l areas in 2007. Although certain measures of reproduction (e.g., reproductive efficiency, nestling health; see above) suggest that farms provide suboptimal breeding habitat in comparison to natura l control areas, more re search is required to determine whether farmlands are source or sink habitat, or even ecological traps. Population source habitat occu rs where high reproductive suc cess results in a population surplus (i.e., excess reproduction prevents any deleterious effects of mortality on population size). Surplus individuals from source habitat em igrate to sink habitat, where reproduction and survivorship are lower than mortality (Brawn and Robinson 1996, Van Dyke 2003). If most bluebird fledglings survived to adulthood on farms, then farms would have not been sink habitat, and they may have even been source habitat. However, we did not monitor juvenile or adult survival in our study. Future research could measure reproductive output, survivorship, and mortality, thereby verifying if farm s serve as source or sink habitat. The assessment of whether or not farms serve as ecological traps al so requires detailed population-level data. An ecological trap is defined as an envi ronment that has been altered suddenly by human activities, [whe re] an organism makes a maladaptive habitat choice based on formerly reliable environmental cues, despite the availability of higher quality habitat (Schlaepfer et al. 2002). In order for farms to be considered ecological traps, bluebirds would have to fare worse on farms than alternative habitat (e.g., natural areas), while simultaneously preferring farms over alternative habitat. Farm s certainly are environments that have been 66

PAGE 67

altered by human activities, and our results s uggest that farms are suboptimal habitat in comparison to natural areas (see above). However, we cannot state that bluebirds make choices in favor of farmland habitat over natural habita t (or vice-versa) because we did not measure habitat preference. Future re search could determine if farms act as ecological traps by monitoring bluebird reproductive success, surviv orship, and mortality on replicate plots of natural open-lands adjacent to farmlands while quantifying competition levels among bluebirds in both of these treatments (there by quantifying habitat preference). We excluded predation from evaluation in our study in order to more precisely assess the potential that food resources varied with land ma nagement (see Methods in Chapters 2 and 3). However, this major source of bluebird mortality (Gowaty and Plissner 1998) may differ between farms and natural areas, potentially affec ting the habitat quality of farms. Predator communities may differ between farms and natural areas, and predation rates of forest-adapted birds are often high on the edges of agri cultural lands (e.g., Rodewald & Yahner 2001 b, Tewksbury et al. 2006). However, such resear ch is limited to a comparison of conventional farms to reduced-impact farms, or conventional farms to natural areas. No research (to our knowledge; Hole et al. 2005, Scherr and McN eely 2008, Watson et al. 2008) has compared predator communities on natural open lands to those on reduced-impact or conventional farms, while focusing on the reproductive success of birds that have evolved in open landscapes (i.e., those that are appropriately ta rgeted by conservation efforts). Conservation biologists must verify if predation levels are substantially higher or lower on farms in comparison to natural areas before subscribing farm lands as conservation areas. Human disturbance is another po tentially important factor in determining the suitability of farmland habitat for wildlife conservation, as it has been shown to inversely correlate with avian 67

PAGE 68

reproductive success (Yasue and Dearden 2006, Ki ght and Swaddle 2007). Farmer activity rarely subsides during the growi ng season this seems especially true on reduced-impact farms, where a variety of crops are grown and harves ted at different times, requiring near-constant activity by farmers (JJD personal observation ). Such disturbance may adversely affect bluebird populations, as bluebird reproductive success has b een shown to decrease with an increase in human disturbance (Kight and Swaddle 2007). The effects of human disturbance on farmland wildlife merits further research, as it will aid in the evaluation of the conservation potential of farms. Spatial scale needs to be considered if res earch is to obtain comp rehensive understanding of the complexities involved with sustaining w ild birds and other vertebrates on agricultural lands (Hole et al. 2005). We c onducted our research on few farms in North-central Florida, and all of our natural open-land sites were located within one large pr otected reserve (raising issues of spatial autocorrelation). Furthermore, the East ern Bluebird is a highly mobile species that is fairly broad in its breeding hab itat selection, including habitats not sampled here (e.g., orchards, graveyards, golf courses; Gowaty and Plissn er 1998). Research conducted over a greater geographic range, with more replicates, and ac ross a diversity of habitats would further strengthen our ability to assess the value of farms as habitat. Finally, many native species adapted to open la ndscapes that inhabi t farmlands are of greater conservation concern than bluebirds, and they deserve the attention of future research (e.g., Loggerhead Shrike [ Lanius ludovicianus; Yosef 1996], Common Ground-Dove [ Columbina passerina ; Bowman 2002], Northern Bobwhite [ Colinus virginianus; Brennan 1999]). A multi-species approach across a variet y of open-land habitats would also improve ecosystem management. It would increase explanatory power while more accurately 68

PAGE 69

69 determining the landscape attributes and a ppropriate management schemes required for conserving birds of open lands (Lambeck 1997). Furthermore, agro-ecosystem designs that encompass biodiversity protection are among the most challenging and relevant problems in conservation biology (Daily et al 2001; Hole et al. 2005). Our research suggests that farms provide s uboptimal breeding habitat in comparison to natural areas, yet farmland bluebird s still produced substa ntial numbers of offspring (see above). By measuring reproductive success alongside survivorship and habitat preference, future research could determine if farms act as habita t sources, sinks, or ecological traps (Brawn and Robinson 1996, Schlaepfer et al. 2002, Van Dyke 2003) Ecologists could further elaborate the effects of farmlands on reproduction, survivorsh ip, and mortality by monitoring predation and human disturbance among farms and natural open la nds. Lastly, future research could increase applicability and generality by focusing on open-land communities of priority conservation concern. Without such data, we cannot yet conc lude that wildlife-friendly farms are truly wildlife-friendly. However, this research is the first to compare avian reproductive success among reduced-impact farms, conventional farms, and natural areas (to our knowledge; Hole et al. 2005, Scherr and McNeely 2008, Watson et al. 2008) and our results certainly illuminate fruitful paths for future research.

PAGE 70

APPENDIX A EFFECTS OF LAND MANAGEMENT ON THE REPRODUCTIVE SUCCESS OF A SONGBIRD OF OPEN LANDS Table A-1. Raw data for pairs that laid a fourth clutch Land Management Brood Incubation Period Eggs Hatchlings Fledglings Conventional 3 17.5 4 3 3 Conventional 3 12 4 2 2 Reduced-Impact 4 unknown 4 2 0 Reduced-Impact would be "3" n/a 4 0 0 The second column indicates whether the clutch in concern was or would have been the actual third or fourth brood. 70

PAGE 71

Table A-2. Site-level descriptive st atistics, presented clutch by clutch SiteID* Clutch Parameter Incubation Period #Eggs #Hatchlings #Fledglings Hatching Success Fledging Success Firsteggday Interbrood Lapse RIF1 1 Mean 15.50 4.00 3.00 3.00 0.75 1.00 43.50 27.00 N 1.00 1.00 1.00 1.00 1.00 1.00 SE . 2 Mean 16.00 3.00 2.00 1.00 0.67 0.50 N 1.00 1.00 1.00 1.00 SE . 3 Mean 13.00 5.00 3.00 3.00 0.60 1.00 N 1.00 1.00 1.00 1.00 SE . Total Mean 14.83 4.00 2.67 2.33 0.67 0.88 N 3.00 3.00 3.00 3.00 SE 0.93 0.58 0.33 0.67 RIF2 1 Mean 14.00 4.67 3.00 3.00 0.64 1.00 60.00 34.50 N 3.00 3.00 3.00 3.00 3.00 2.00 SE 0.58 0.33 0.58 0.58 7.00 2 Mean 9.00 3.50 2.00 2.00 0.57 1.00 N 1.00 2.00 2.00 2.00 SE 1.50 2.00 2.00 3 Mean 14.00 4.00 1.00 1.00 0.25 1.00 N 1.00 1.00 1.00 1.00 SE . Total Mean 13.00 4.17 2.33 2.33 0.56 1.00 N 5.00 6.00 6.00 6.00 SE 1.05 0.48 0.67 0.67 RIF3 1 Mean 14.40 4.60 4.00 3.75 0.87 0.94 64.20 30.60 N 5.00 5.00 5.00 4.00 5.00 5.00 SE 0.53 0.40 0.45 0.48 6.39 7.36 2 Mean 13.60 4.60 3.00 2.80 0.65 0.93 N 5.00 5.00 5.00 5.00 SE 0.24 0.24 0.55 0.49 3 Mean 14.00 4.33 2.33 2.33 0.54 1.00 N 2.00 3.00 3.00 3.00 SE 1.00 0.33 1.20 1.20 Total Mean 14.00 4.54 3.23 3.00 0.71 0.93 N 12.00 13.00 13.00 12.00 SE 0.28 0.18 0.39 0.39 RIF4 1 Mean 14.00 4.75 3.75 3.67 0.79 0.98 47.25 34.67 N 4.00 4.00 4.00 3.00 4.00 3.00 SE 0.00 0.25 0.48 0.67 0.25 5.77 2 Mean 13.75 4.75 2.25 2.25 0.47 1.00 N 4.00 4.00 4.00 4.00 SE 0.48 0.25 0.63 0.63 3 Mean 14.00 4.33 2.00 1.67 0.46 0.83 N 3.00 3.00 3.00 3.00 SE 1.00 0.33 0.00 0.33 Total Mean 13.91 4.64 2.73 2.50 0.59 0.92 N 11.00 11.00 11.00 10.00 SE 0.28 0.15 0.36 0.40 71

PAGE 72

Table A-2 Continued SiteID* Clutch Parameter Incubation Period #Eggs #Hatchlings #Fledglings Hatching Success Fledging Success Firsteggday Interbrood Lapse RIF5 1 Mean 13.50 6.00 4.00 4.00 0.67 1.00 56.00 38.50 N 1.00 1.00 1.00 1.00 1.00 1.00 SE . 2 Mean 10.00 5.00 4.00 0.00 0.80 0.00 N 1.00 1.00 1.00 1.00 SE . 3 Mean 12.00 4.00 3.00 3.00 0.75 1.00 N 1.00 1.00 1.00 1.00 SE . Total Mean 11.83 5.00 3.67 2.33 0.73 0.64 N 3.00 3.00 3.00 3.00 SE 1.01 0.58 0.33 1.20 RIF6 1 Mean 14.50 5.00 3.33 3.33 0.67 1.00 51.83 32.50 N 2.00 3.00 3.00 3.00 3.00 2.00 SE 0.00 0.00 1.67 1.67 4.17 0.71 2 Mean 12.33 4.67 4.33 4.33 0.93 1.00 N 3.00 3.00 3.00 3.00 SE 0.73 0.33 0.33 0.33 3 Mean 13.50 4.00 4.00 4.00 1.00 1.00 N 2.00 2.00 2.00 2.00 SE 0.50 0.00 0.00 0.00 Total Mean 13.29 4.63 3.88 3.88 0.84 1.00 N 7.00 8.00 8.00 8.00 SE 0.47 0.18 0.58 0.58 RIF7 1 Mean 13.75 4.50 4.50 4.50 1.00 1.00 66.75 30.00 N 2.00 2.00 2.00 2.00 2.00 2.00 SE 0.25 0.50 0.50 0.50 16.75 7.07 2 Mean 13.00 4.50 3.50 2.50 0.78 0.71 N 2.00 2.00 2.00 2.00 SE 1.00 0.50 1.50 2.50 3 Mean 13.00 4.00 3.00 3.00 0.75 1.00 N 1.00 1.00 1.00 1.00 SE . Total Mean 13.30 4.40 3.80 3.40 0.86 0.89 N 5.00 5.00 5.00 5.00 SE 0.37 0.24 0.58 0.93 RIF8 1 Mean 13.00 5.00 5.00 5.00 1.00 1.00 49.00 33.00 N 1.00 1.00 1.00 1.00 1.00 1.00 SE . 2 Mean 13.00 5.00 4.00 4.00 0.80 1.00 N 1.00 1.00 1.00 1.00 SE . 3 Mean 12.00 5.00 5.00 5.00 1.00 1.00 N 1.00 1.00 1.00 1.00 SE . Total Mean 12.67 5.00 4.67 4.67 0.93 1.00 N 3.00 3.00 3.00 3.00 SE 0.33 0.00 0.33 0.33 72

PAGE 73

Table A-2 Continued SiteID* Clutch Parameter Incubation Period #Eggs #Hatchlings #Fledglings Hatching Success Fledging Success Firsteggday Interbrood Lapse CF1 1 Mean 15.00 4.50 2.00 2.00 0.44 1.00 50.00 25.00 N 1.00 2.00 2.00 2.00 2.00 1.00 SE 0.50 2.00 2.00 6.00 2 Mean 13.50 5.00 3.50 5.00 0.70 1.43 N 2.00 2.00 2.00 1.00 SE 0.50 0.00 1.50 3 Mean 4.00 0.00 0.00 0.00 N 1.00 1.00 1.00 SE Total Mean 14.00 4.60 2.20 2.25 0.48 1.02 N 3.00 5.00 5.00 4.00 SE 0.58 0.24 1.02 1.31 CF2 1 Mean 15.50 4.67 4.00 3.67 0.86 0.92 69.67 37.00 N 3.00 3.00 3.00 3.00 3.00 3.00 SE 0.87 0.33 0.58 0.67 8.21 2.18 2 Mean 13.83 4.00 4.00 4.00 1.00 1.00 N 3.00 3.00 3.00 3.00 SE 0.17 0.00 0.00 0.00 3 Mean 13.00 4.00 4.00 1.00 0.00 N 1.00 1.00 1.00 SE Total Mean 14.43 4.29 4.00 3.83 0.93 0.96 N 7.00 7.00 7.00 6.00 SE 0.52 0.18 0.22 0.31 CF3 1 Mean 15.00 5.50 1.50 1.00 0.27 0.67 62.50 23.00 N 1.00 2.00 2.00 2.00 2.00 1.00 SE 0.50 1.50 1.00 16.50 2 Mean 14.00 5.00 1.00 1.00 0.20 1.00 N 1.00 2.00 2.00 2.00 SE 0.00 1.00 1.00 3 Mean 13.00 4.00 3.00 3.00 0.75 1.00 N 1.00 1.00 1.00 1.00 SE . Total Mean 14.00 5.00 1.60 1.40 0.32 0.88 N 3.00 5.00 5.00 5.00 SE 0.58 0.32 0.68 0.60 CF4 1 Mean 15.50 4.33 3.00 3.00 0.69 1.00 50.67 34.67 N 3.00 3.00 3.00 3.00 3.00 3.00 SE 0.76 0.33 1.00 1.00 3.18 5.53 2 Mean 14.67 4.67 2.00 2.00 0.43 1.00 N 3.00 3.00 3.00 3.00 SE 0.67 0.33 1.00 1.00 3 Mean 14.00 4.00 1.00 1.00 0.25 1.00 N 2.00 3.00 3.00 3.00 SE 0.00 0.00 0.58 0.58 Total Mean 14.81 4.33 2.00 2.00 0.46 1.00 N 8.00 9.00 9.00 9.00 SE 0.40 0.17 0.53 0.53 73

PAGE 74

Table A-2 Continued SiteID* Clutch Parameter Incubation Period #Eggs #Hatchlings #Fledglings Hatching Success Fledging Success Firsteggday Interbrood Lapse CF5 1 Mean 13.00 3.00 2.00 2.00 0.67 1.00 39.00 34.00 N 1.00 1.00 1.00 1.00 1.00 1.00 SE . 2 Mean 2.00 0.00 0.00 0.00 N 1.00 1.00 1.00 SE 3 Mean 13.00 3.00 1.00 1.00 0.33 1.00 N 1.00 1.00 1.00 1.00 SE . Total Mean 13.00 2.67 1.00 1.00 0.38 1.00 N 2.00 3.00 3.00 3.00 SE 0.00 0.33 0.58 0.58 CF6 1 Mean 14.75 4.50 4.00 4.00 0.89 1.00 42.75 28.00 N 2.00 2.00 2.00 2.00 2.00 2.00 SE 0.75 0.50 1.00 1.00 2.75 4.24 2 Mean 13.25 5.00 4.50 4.00 0.90 0.89 N 2.00 2.00 2.00 2.00 SE 0.75 0.00 0.50 1.00 3 Mean 13.00 4.00 3.50 4.00 0.88 1.14 N 2.00 2.00 2.00 1.00 SE 1.00 0.00 0.50 Total Mean 13.67 4.50 4.00 4.00 0.89 1.00 N 6.00 6.00 6.00 5.00 SE 0.51 0.22 0.37 0.45 NC1 1 Mean 15.50 4.50 4.50 4.50 1.00 1.00 69.00 39.50 N 2.00 2.00 2.00 2.00 2.00 2.00 SE 1.50 0.50 0.50 0.50 3.00 10.61 2 Mean 14.25 4.00 4.00 4.00 1.00 1.00 N 2.00 2.00 2.00 2.00 SE 0.25 0.00 0.00 0.00 Total Mean 14.88 4.25 4.25 4.25 1.00 1.00 N 4.00 4.00 4.00 4.00 SE 0.72 0.25 0.25 0.25 NC2 1 Mean 14.38 4.60 3.40 3.20 0.74 0.94 77.40 40.83 N 4.00 5.00 5.00 5.00 5.00 3.00 SE 0.24 0.24 0.87 0.86 4.01 2.57 2 Mean 14.50 4.25 4.00 3.75 0.94 0.94 N 4.00 4.00 4.00 4.00 SE 0.35 0.25 0.41 0.48 Total Mean 14.44 4.44 3.67 3.44 0.83 0.94 N 8.00 9.00 9.00 9.00 SE 0.20 0.18 0.50 0.50 74

PAGE 75

75 Table A-2 Continued SiteID* Clutch Parameter Incubation Period #Eggs #Hatchlings #Fledglings Hatching Success Fledging Success Firsteggday Interbrood Lapse NC3 1 Mean 15.25 4.80 4.00 4.00 0.83 1.00 63.80 39.75 N 4.00 5.00 4.00 4.00 5.00 4.00 SE 0.43 0.20 0.41 0.41 5.44 7.05 2 Mean 14.80 4.40 3.80 3.40 0.86 0.89 N 5.00 5.00 5.00 5.00 SE 0.46 0.24 0.20 0.24 Total Mean 15.00 4.60 3.89 3.67 0.85 0.94 N 9.00 10.00 9.00 9.00 SE 0.31 0.16 0.20 0.24 NC4 1 Mean 16.00 3.50 2.50 2.50 0.71 1.00 63.75 41.00 N 1.00 2.00 2.00 2.00 2.00 1.00 SE 1.50 2.50 2.50 3.75 2 Mean 13.00 5.00 5.00 5.00 1.00 1.00 N 2.00 2.00 2.00 1.00 SE 2.00 0.00 0.00 3 Mean 12.50 4.00 4.00 4.00 1.00 1.00 N 1.00 1.00 1.00 1.00 SE . Total Mean 13.63 4.20 3.80 3.50 0.90 0.92 N 4.00 5.00 5.00 4.00 SE 1.14 0.58 0.97 1.19 RIF=reduced-impact farm, CF=conventi onal farm, NC=natural control.

PAGE 76

Table A-3. Rainfall patterns in North-central Florida Parameter Feb-Apr Feb-Aug 8-year Mean Rainfall 7.44 10.64 Confidence Interval 2.14 1.89 Lower Bound 5.29 8.75 Upper Bound 9.58 12.53 2007 Mean Rainfall 4.46 9.10 2008 Mean Rainfall 10.74 14.16 Data used from Putnam Hall station of Flor ida Automated Weather Network (FAWN 2008). Values were calculated from data between Fe bruary and April (second column) and February and August (third column), between 2001 and 2008. 76

PAGE 77

APPENDIX B REDUCED-IMPACT FARMING, PREY BIOM ASS, AND THE REPRODUCTIVE SUCCESS OF EASTERN BLUEBIRDS ( SIALIA SIALIS ) 77

PAGE 78

Table B-1. Site-level descriptive statistics Site Parameter First Egg Day Clutches FirstClutch Eggs FirstClutch Hatchlings PB GW Biomass PB WB Biomass LT GW Biomass LT WB Biomass LT GW Instability LT WB Instability C1 GW Biomass C1 WB Biomass C1 GW Instability C1 WB Instability RIF2 Mean 51.2 2.25 4.8 2.6 7.50 5.59 23.11 18.90 4.70 23.11 6.71 5.57 4.75 4.70 N 5 4 5 5 . . Std. Deviation 17.81 0.50 0.45 1.95 . . RIF3 Mean 37.58 3 4.17 2 7.63 11.82 22.30 15.24 13.54 22.30 11.59 19.06 14.52 13.54 N 6 5 6 6 . . Std. Deviation 8.30 1.22 0.98 1.10 . . RIF4 Mean 38 3.25 4.5 2 7.69 6.81 13.03 18.39 14.74 13.03 10.38 12.45 8.10 14.74 N 4 4 4 4 . . Std. Deviation 9.42 0.96 1 1.83 . . RIF9 Mean 46.25 3 3.5 2.5 17.75 21.00 26.53 35.20 36.53 26.53 22.59 44.20 15.15 36.53 N 2 2 2 2 . . Std. Deviation 5.30 0 0.71 2.12 . . NC1 Mean 72 2.75 4.75 3.25 1.88 4.50 11.50 13.65 9.37 11.50 12.56 14.39 3.61 9.37 N 4 4 4 4 . . Std. Deviation 11.43 0.96 0.50 2.22 . . NC2 Mean 80.93 1.86 4.29 3.71 1.88 4.50 9.48 9.77 4.15 9.48 15.60 9.00 8.21 4.15 N 7 7 7 7 . . Std. Deviation 24.02 0.69 0.76 1.80 . . NC3 Mean 58.5 2 4.25 3.25 6.50 9.06 9.86 10.44 11.35 9.86 4.71 13.19 3.65 11.35 N 4 3 4 4 . . Std. Deviation 1.91 0 1.5 2.36 . . NC4 Mean 45 3 4.5 4.5 20.77 15.08 17.29 16.48 8.49 17.29 20.57 22.44 16.76 8.49 N 2 1 2 2 . . Std. Deviation 0 0.71 0.71 . . NC5 Mean 61.5 3 4 4 4.50 2.17 11.26 11.06 4.67 11.26 12.26 13.65 10.04 4.67 N 2 2 2 2 . . Std. Deviation 0.71 0 0 0 . . NC6 Mean 53.5 3 5 4.5 7.75 4.25 8.10 14.06 11.33 8.10 10.72 14.94 8.11 11.33 N 2 2 2 2 . . Std. Deviation 3.54 0 0 0.71 . . 78 RIF=reduced-impact farm; NC=natural cont rol area; GW=grasshopper walk survey; WB =walk-brush survey; PB=pre-breeding; LT=long-term; C1=first-clutch. We used so me of the same sites from our previous study, as well as some new sites (see Table A-2).

PAGE 79

79Table B-2. Chapter 3 definitions Term Definition First Egg Day The day that the first egg of the first clutch of pair was laid Clutch Production The total number of clutches produced per pair First-clutch Egg Production The tota l number of hatchlings produced per pair in the first clutch First-clutch Hatchling Production The total number of eggs pr oduced per pair in the first clutch Pre-breeding Adjective denoting the time period (when arthropod sampling began and before bluebird breeding began) between February 17th and Marc h 13th (the mean firstegg-date for reducedimpact farms [the land management type with th e earlier mean first-egg-date]); This time period is the same for all sites First-clutch Adjective denoting the time peri od between the two weeks before and the two weeks after the mean first-egg-date for a given site; This time period varies site-by-site Long-term Adjective denoting the time peri od between the February 17th a nd June 1st, the entire period when arthropod sampling occurred; This time period is the same for all sites Prey Biomass Absolute number of prey encountered on a transect multiplied by the mean prey length for that transect (see methods for details on determining prey length); Averaged on a site-by-site basis in the calculation of pre-breed ing, first-clutch, and long-te rm prey biomass indices Prey Instability The coefficient of variation (CV) of prey biom ass; Equal to the standa rd deviation divided by the square root of the mean; Calculated on a site-by-site basis for pre-br eeding, first-clutch, and long-term prey instability indices GW Adjective denoting "Grasshopper Walk surveys; see Methods for details WB Adjective denoting "Walk-brush" surveys; see Methods for details

PAGE 80

LITERATURE CITED Albrecht, T. 2004. Edge effect in wetland-arable land boundary de termines nesting success of scarlet rosefinches ( Carpodacus erythrinus ) in the Czech Republic. Auk 121:361-371. Bignal, E. M., and D. I. McCracken. 1996. Low-inte nsity farming systems in the conservation of the countryside. Journal of Applied Ecology 33:413-424. Bishop, C. A., B. Collins, P. Mineau, N. M. Burgess, W. F. Read, and C. Risley. 2000. Reproduction of cavity-nesting bi rds in pesticide-sprayed apple orchards in southern Ontario, Canada, 1988-1994. Environmental Toxicology and Chemistry 19:588-599. Bishop, C. A., P. Ng, P. Mineau, J. S. Quinn, a nd J. Struger. 2000. Effect s of pesticide spraying on chick growth, behavior, and pare ntal care in tree swallows ( Tachycineta bicolor ) nesting in an apple orchard in Ontario, Cana da. Environmental Toxicology and Chemistry 19:2286-2297. Blanco, G., J. Martinez-Padilla, J. A. Davila, D. Serrano, and J. Vinuela. 2003. First evidence of sex differences in the duration of avian embryonic period: consequences for sibling competition in sexually dimorphic birds. Behavioral Ecology 14:702-706. Borkhataria, R. R., J. A. Collazo, and M. J. Groom. 2006. Additive effects of vertebrate predators on insects in a Puerto Rican co ffee plantation. Ecological Applications 16:696703. Bouvier, J. C., J. F. Toubon, T. Boivin, a nd B. Sauphanor. 2005. Effects of apple orchard management strategies on the great tit ( Parus major) in southeastern France. Environmental Toxicology and Chemistry 24:2846-2852. Bowman, R., Ed. 2002. Common Ground-Dove ( Columbina passerina ). The Birds of North America. Cornell Lab of Ornithology, Ithaca. Brennan, L. A., Ed. 1999. Northern Bobwhite ( Colinus virginianus ). The Birds of North America. Cornell Lab of Ornithology, Ithaca. Brawn, J. D., and S. K. Robinson. 1996. Source-sink population dynamics may complicate the interpretation of long-term census data. Ecology 77:3-12. Brickle, N. W., D. G. C. Harper, N. J. Ae bischer, and S. H. Cockayne. 2000. Effects of agricultural intensification on the breeding success of corn buntings Miliaria calandra. Journal of Applied Ecology 37:742-755. Britschgi, A., R. Spaar, and R. Arlettaz. 2006. Imp act of grassland farming intensification on the breeding ecology of an indicator ins ectivorous passerine, the Whinchat ( Saxicola rubetra): Lessons for overall Alpine meadowland ma nagement. Biological Conservation 130:193205. 80

PAGE 81

Clark, M. E., and T. E. Martin. 2007. Modeling tradeoffs in avian life history traits and consequences for population growt h. Ecological Modeling 209:110-120. Daily, G. C., P. R. Ehrlich, and G. A. Sanchez-Azofeifa. 2001. Countryside biogeography: Use of human-dominated habitats by the avifa una of southern Costa Rica. Ecological Applications 11:1-13. Davis, S. E., R. G. Nager, and R. W. Furness. 2005. Food availability affects adult survival as well as breeding success of Parasitic Jaegers. Ecology 86:1047-1056. Deerenberg, C., V. Apanius, S. Daan, and B. N. 1997. Reproductive effort decreases antibody responsiveness Proceedings of the Royal Soci ety of London Series B-Biological Sciences 264:2021-2029. Elmberg, J., P. Nummi, H. Poysa, G. Gunnar sson, and K. Sjoberg. 2005. Early breeding teal ( Anas crecca ) use the best lakes and have the hi ghest reproductive success. Annales Zoologici Fennici 42:37-43. Fauth, P. T. 2001. Wood Thrush populations are not all sinks in the ag ricultural midwestern United States. Conser vation Biology 15:523-527. FAWN (Florida Automated Weather Network). 2008. Archived Weather Data. http://fawn.ifas.ufl.edu/, University of Florida, Gainesville, FL. Feber, R. E., L. G. Firbank, P. J. Johnson, and D. W. Macdonald. 1997. The effects of organic farming on pest and non-pest butterfly abundanc e. Agriculture Ecosystems & Environment 64:133-139. Fischer, J., B. Brosi, G. C. Daily, P. R. Ehrlic h, R. Goldman, J. Goldstein, D. B. Lindenmayer, A. D. Manning, H. A. Mooney, L. Pejchar, J. Ranganathan, and H. Tallis. 2008. Should agricultural policies encourage land sparing or wildlife-friendly farming? Frontiers in Ecology and the Environment 6:380-385. Ford, T. B., D. E. Winslow, D. R. Whitehea d, and M. A. Koukol. 2001. Reproductive success of forest-dependent songbirds near an agricultural corridor in south-central Indiana. Auk 118:864-873. Gardiner, T., J. Hill, and D. Chesmore. 2005. Review of the methods frequently used to estimate the abundance of Orthoptera in grassland ecosystems. Journal of Insect Conservation 9:151-173. Gowaty, P. A., and J. H. Plissner., Ed. 1998. Eastern Bluebird ( Sialia sialis ). The Birds of North America. Cornell Lab of Ornithology, Ithaca. Graham, D. J., and J. L. Desgranges. 1993. Effects of the organophosphate azinphos-methyl on birds of potato fields and apple orchards in Quebec, Canada. Agriculture Ecosystems & Environment 43:183-199. 81

PAGE 82

Grankvist, G., and A. Biel. 2001. The importance of be liefs and purchase criter ia in the choice of eco-labeled food products. Journal of Environmental Psychology 21:405-410. Green, R. E., S. J. Cornell, J. P. W. Scharlemann, and A. Balmford. 2005. Farming and the fate of wild nature. Science 307:550-555. Greenberg, R., P. Bichier, A. C. Angon, C. MacVean, R. Perez, and E. Cano. 2000. The impact of avian insectivory on arthropods and l eaf damage in some Guatemalan coffee plantations. Ecology 81:1750-1755. Gustafsson, L., D. Nordling, M. S. Andersson, B. C. Sheldon, and A. Qvarnstrom. 1994. Infectious-diseases, reproductive effort, and the cost of reproduction in birds. Philosophical Transactions of the Royal Society of L ondon Series B-Biological Sciences 346:323-331. Hall, L., S., P. R. Krausman, and M. L. Morrison. 1997. The habitat concept and a plea for standard terminology. Wildlife Society Bulletin 25: 173-182. Hart, J. D., T. P. Milsom, G. Fisher, V. Wilkin s, S. J. Moreby, A. W. A. Murray, and P. A. Robertson. 2006. The relationship between yellowhammer breeding performance, arthropod abundance and insectic ide applications on arable farmland. Journal of Applied Ecology 43:81-91. Hatchwell, B. J., D. E. Chamberlain, and C. M. Perrins. 1996. The demography of blackbirds ( Turdus merula ) in rural habitats: Is farmland a suboptimal habitat? Journal of Applied Ecology 33:1114-1124. Hepp, G. R., R. A. Kennamer, and M. H. Johnson. 2006. Maternal effects in Wood Ducks: Incubation temperature influences incubati on period and neonate phenotype. Functional Ecology 20:307-314. Hole, D. G., A. J. Perkins, J. D. Wilson, I. H. Alexander, F. Grice, and A. D. Evans. 2005. Does organic farming benefit biodiversity? Biological Conser vation 122:113-130. Hooks, C. R. R., R. R. Pandey, and M. W. Johnson. 2003. Impact of avian and arthropod predation on lepidopteran cater pillar densities and plant pr oductivity in an ephemeral agroecosystem. Ecological Entomology 28:522-532. Jacobson, S. K., K. E. Sieving, G. A. Jones, and A. Van Doorn. 2003. Assessment of farmer attitudes and behavioral intentions toward bird conservati on on organic and conventional Florida farms. Conser vation Biology 17:595-606. Jakob, E. M., S. D. Marshall, and G. W. Uetz. 1996. Estimating fitness: A comparison of body condition indices. Oikos 77:61-67. Jones, G. A., and K. E. Sieving. 2006. Intercropp ing sunflower in organic vegetables to augment bird predators of arthropods. Agricu lture Ecosystems & Environment 117:171-177. 82

PAGE 83

Jones, G. A., K. E. Sieving, and S. K. Jac obson. 2005. Avian diversity an d functional insectivory on north-central Florida farmla nds. Conservation Biology 19:1234-1245. Kight, C. R., and J. P. Swaddle. 2007. Associati ons of anthropogenic activity and disturbance with fitness metrics of eastern bluebirds ( Sialia sialis ). Biological Conservation 138:189197. Knutson, M. G., G. J. Niemi, W. E. Newton, and M. A. Friberg. 2004. Avian nest success in midwestern forests fragmented by agriculture. Condor 106:116-130. Korpimaki, E. 1992. Diet composition, prey choice, and breeding success of Long-eared Owls: Effects of multiannual fluctuations in f ood abundance. Canadian Journal of ZoologyRevue Canadienne De Zoologie 70:2373-2381. Lambeck, R. J. 1997. Focal species: A multi-sp ecies umbrella for nature conservation. Conservation Biology 11:849-856. LeClerc, J. E., J. P. K. Che, J. P. Swaddl e, and D. A. Cristol. 2005. Reproductive success and developmental stability of eastern bluebirds on golf courses: Evidence that golf courses can be productive. Wildlife Society Bulletin 33:483-493. Lindstrom, A., A. Enemar, G. Andersson, T. von Proschwitz, and N. E. I. Nyholm. 2005. Density-dependent reproductive output in relation to a drastically varying food supply: getting the density measure right. Oikos 110:155-163. Londono, G. A., D. J. Levey, and S. K. Robinson. 2008. Effects of temperature and food on incubation behaviour of the northern mockingbird (Mimus polyglottos). Animal Behaviour 76:669-677. Martin, T. E. 1987. Food as a limit on breeding bird s: A life-history perspective. Annual Review of Ecology and Systematics 18:453-487. Mayne, G. J., C. A. Bishop, P. A. Martin, H. J. Boermans, and B. Hunter. 2005. Thyroid function in nestling tree swallows and eastern bluebird s exposed to non-persistent pesticides and p,p '-DDE in apple orchards of southern Ontario, Canada. Ecotoxicology 14:381-396. Mayne, G. J., P. A. Martin, C. A. Bishop, and H. J. Boermans. 2004. Stress and immune responses of nestling tree swallows ( Tachycineta bicolor ) and eastern bluebirds ( Sialia sialis ) exposed to nonpersistent pesticides and p,p,'-dichlorodiphenyldichloroethylene in apple orchards of southern Ontario, Cana da. Environmental Toxicology and Chemistry 23:2930-2940. McCleery, R., Y. Yom-Tov, and D. Purchase. 1998. Th e effect of annual rainfall on the survival rates of some Australian passerines. Journal of Field Ornithology 69:169-179. Moller, A. P. 2007. Interval between clutches, fi tness, and climate change. Behavioral Ecology 18:62-70. 83

PAGE 84

Mols, C. M. M., and M. E. Visser. 2002. Great tits can reduce caterpillar damage in apple orchards. Journal of A pplied Ecology 39:888-899. Navara, K. J., G. E. Hill, and M. T. Mendon ca. 2005. Variable effects of yolk androgens on growth, survival, and immun ity in eastern bluebird nestlings. Physiological and Biochemical Zoology. 78:570-578. Nebel, B. J., and R. T. Wright. 1993. Environmental Science: The Way the World Works, Fourth ed. Prentice Hall PT R, Upper Saddle River, NJ. Nemeckova, I., V. Mrlik, and P. Drozd. 2008. Ti ming of breeding, habitat preference and reproductive success of marsh harriers ( Circus aeruginosus ). Biologia 63:261-265. Nilsson, J. A., and E. Svensson. 1996. The cost of reproduction: A ne w link between current reproductive effort and future reproductive su ccess. Proceedings of the Royal Society of London Series B-Biological Sciences 263:711-714. North American Bluebird Society. 2008. Nest box plans. http://www.nabluebirdsoci ety.org/nestboxplans.htm North American Bluebird Society, Miamiville, OH NOAA (National Oceanic and Atmospheric Administration). 2008. The onset of the wet and dry seasons in East Central florida: A subtropical wet-dry climate? http://www.srh.noaa.gov/mlb/wetdry/We tDry.htm, NOAA, Melbourne, FL. Nooker, J. K., P. O. Dunn, and L. A. Whitti ngham. 2005. Effects of food abundance, weather, and female condition on reproduction in tree swallows ( Tachycineta bicolor ). Auk 122:1225-1238. Oleske, D. L., R. J. Robel, and K. E. Kemp. 1997. Sweepnet-collected inve rtebrate biomass from highand low-input agricultura l fields in Kansas. Wildlif e Society Bulletin 25:133-138. Patnode, K. A., and D. H. White. 1991. Effects of pesticides on songbird productivity in conjunction with pecan cultivation in southern Georgia: A multiple-exposure experimental design. Environmental Toxicology and Chemistry 10:1479-1486. Peak, R. G., F. R. Thompson, and T. L. Shaffer. 2004. Factors affecting songbi rd nest survival in Riparian forests in a midwestern agricultural lands cape. Auk 121:726-737. Phillips, A. 2002. Management Guidelines for IUCN Category V Protected Areas Protected Landscapes/Seascapes. Best Pr actice Protected Areas Guid elines Series, No. 9. 122 pp. Phillips, R. A., R. W. G. Caldow, and R. W. Furness. 1996. The influence of food availability on the breeding effort and reproductive success of Arctic Skuas ( Stercorarius parasiticus). Ibis 138:410-419. 84

PAGE 85

Pimentel, C., and J. A. Nilss on. 2007. Response of Great Tits ( Parus major ) to an irruption of a Pine Processionary Moth ( Thaumetopoea pityocampa ) population with a shifted phenology. Ardea 95:191-199. Raberg, L., M. Grahn, D. Hasselquist, and E. Svensson. 1998. On the adaptive significance of stress-induced immunosuppression. Proceedings of the Royal Society of London Series BBiological Sciences 265:1637-1641. Richner, H., P. Christe, and A. Oppliger. 1995. Pate rnal investment affect prevalence of malaria. Proceedings of the National Academy of Scie nces of the United States of America 92:1192-1194. Rodewald, A. D., and R. H. Yahner. 2001. Avia n nesting success in forested landscapes: Influence of landscape composition, stand a nd nest-patch microhabitat, and biotic interactions. Auk 118:1018-1028. Rodewald, A. D., and R. H. Yahner. 2001. Influence of landscape composition on avian community structure and associat ed mechanisms. Ecology 82:3493-3504. Rodl, T. 1999. Environmental factors determine numbers of over-wintering European Stonechats ( Saxicola rubicola ): A long term study. Ardea 87:247-259. Scherr, S. J., and J. A. McNeely. 2008. Biodiversity conservation and agri cultural sustainability: Towards a new paradigm of ecoagriculture la ndscapes. Philosophical Transactions of the Royal Society B-Biological Sciences 363:477-494. Schlaepfer, M. A., M. C. Runge, and P. W. Sher man. 2002. Ecological and evolutionary traps. Trends in Ecology and Evolution 17: 474-480. Sekercioglu, C. H., S. R. Loarie, F. O. Brenes P. R. Ehrlich, and G. C. Daily. 2007. Persistence of forest birds in the Costa Rican agricultural countryside. Conservation Biology 21:482494. Slagsvold, T. 1984. Clutch size variation of birds in relation to nest predat ion: On the cost of reproduction. Journal of Animal Ecology 53:945-953. Stanback, M. T., and M. L. Seifert. 2005. A comparison of easter n bluebird reproductive parameters in golf and rural habitats Wildlife Society Bulletin 33:471-482. Tewksbury, J. J., L. Garner, S. Garner, J. D. Lloyd, V. Saab, and T. E. Martin. 2006. Tests of landscape influence: Nest predation and br ood parasitism in fragmented ecosystems. Ecology 87:759-768. Tilman, D., J. Fargione, B. Wolff, C. D'Ant onio, A. Dobson, R. Howart h, D. Schindler, W. H. Schlesinger, D. Simberloff, and D. Swac khamer. 2001. Forecasting agriculturally driven global environmental change. Science 292:281-284. 85

PAGE 86

86 Tinbergen, J. M. 1987. Costs of reproduction in the Great Tit: Intraseasonal costs associated with brood size. Ardea 75:111-122. Valkama, J., E. Korpimaki, A. Holm, and H. Hakkarainen. 2002. Hatching asynchrony and brood reduction in Tengmalm's owl ( Aegolius funereus ): The role of temporal and spatial variation in food abundan ce. Oecologia 133:334-341. Van Dyke, F. 2003. Conservation Biology: Foundations, Concepts, Applications, First ed. McGraw-Hill, New York. Verhulst, S., and J. A. Nilsson. 2008. The timing of birds' breeding seasons: A review of experiments that manipulated timing of breed ing. Philosophical Transactions of the Royal Society B-Biological Sciences 363:399-410. USDA Natural Resources Conservati on Service. 1999. Eastern Bluebird ( Sialia sialis ) Fish and Wildlife Habitat Management Leaflet. 12 p. Watson, C. A., R. L. Walker, and E. A. St ockdale. 2008. Research in organic production systems: Past, present, and future. Jo urnal of Agricultura l Science 146:1-19. Wild Farm Alliance. 2005. Maintaining or Im proving Natural Resources Amendment to NOSB Organic System Plan Template. http://www.wildfarmalliance.org/resources /nosb_biodiv.pdf, Wild Farm Alliance, Watsonville, CA. Wilson, J. D., J. Evans, S. J. Browne, and J. R. King. 1997. Territory di stribution and breeding success of skylarks ( Alauda arvensis ) on organic and intensive farmland in southern England. Journal of A pplied Ecology 34:1462-1478. Yasue, M., and P. Dearden. 2006. The effects of heat stress, predati on risk and parental investment on Malaysian plover nest return times following a human disturbance. Biological Conservation 132:472-480. Yosef, R., Ed. 1996. Loggerhead Shrike ( Lanius ludovicianus ). The Birds of North America. Cornell Lab of Ornithology, Ithaca. Zuria, I., J. E. Gates, and I. Castellanos. 2007. Artificial nest predation in hedgerows and scrub forest in a human-dominated landscape of cen tral Mexico. Acta Oecologica-International Journal of Ecology 31:158-167.

PAGE 87

BIOGRAPHICAL SKETCH I focus on wildlife (especially bird) species and communities to address problems in applied ecological research, cons ervation, and natural resources ma nagement. I have worked in organismal biology, population and comm unity ecology, agroecology, urban ecology, conservation ornithology, long-term monitoring projects, and the human dimensions of wildlife management. I have worked in a variety of landscapes in North and South America. Study species range from aquatic macroinvertebrates to ta pirs. I graduated with a Bachelor of Arts in environmental science and zoology fr om Miami University of Ohio. 87