TECHNICAL REPORT NO. 13
FLORIDA GRASSHOPPER SPARROW STATUS SURVEY
by
Michael F. Delany and Jeffrey A. Cox*
Florida Game and Fresh Water Fish Commission
Wildlife Research Laboratory
4005 South Main Street
Gainesville, FL 32601
and
*Florida State Museum
University of Florida
Gainesville, FL 32611
Supported by:
Jacksonville Endangered Species Office
U.S. Fish and Wildlife Service
2747 Art Museum Drive
Jacksonville, Florida 32207
Research Work Order No. 14
March 1985
TABLE OF CONTENTS
LIST OF FIGURES ii
LIST OF TABLES iii
INTRODUCTION 1
PROCEDURES 4
RESULTS AND DISCUSSION 7
CONCLUSION AND RECOMMENDATIONS 11
1. Status of species 11
2. Essential habitat 13
3. Management and recovery 14
4. Taxonomy 16
5. Impact of Federal activity 16
6. Research needs 17
LITERATURE CITED 18
ACKNOWLEDGEMENTS 21
LIST OF FIGURES
Range of the grasshopper sparrow
Florida grasshopper sparrow habitat
Florida grasshopper sparrow
Florida grasshopper sparrow location
Florida grasshopper sparrow location
Florida grasshopper sparrow location
Okeechobee counties
Florida grasshopper sparrow location
Florida grasshopper sparrow location
ns, 1984
ns in Osceola County
ns in Highlands and
ns in Glades County
ns in Polk County
Figure
1
2
3
4
5
6
7
8
Page
22
23
23
24
25
26
27
28
LIST OF TABLES
Table Page
1 Bird numbers and general habitat characteristics 29
at nine sites occupied by Florida grasshopper
sparrows, 1980-1984.
2 Frequency of occurrence for plants at 32 Florida 31
grasshopper sparrow territories (320 m2 plots),
15 April to 15 June 1982.
3 Structural characteristics of Florida grasshopper 33
sparrow territories (N=32) in Osceola, Okeechobee,
and Highlands counties, 15 May 15 June, 1981-1982.
4 Comparison of the vegetative structure of 24 Florida 34
grasshopper sparrow territories on three pastures,
Avon Park Wildlife Management Area, 1982.
5 Florida grasshopper sparrow populations currently 35
extant, 1984.
A. INTRODUCTION
The grasshopper sparrow (Ammodramus savannarum) occurs throughout
most of temperate North America (Figure 1), but is confined to low to
medium height grassland plant communities (Smith 1963). The Florida
subspecies (A. s. floridanus) is geographically isolated from the eastern
race (A. s. pratensis) by at least 500 km (AOU 1983) and appears to be
limited in distribution to the prairie region of south-central Florida.
The Florida subspecies was discovered in 1901 by Edgar A. Mearns at
a location "on the Kissimmee Prairie, 7 miles east of Alligator Bluff, Osceola
County, Florida" (Mearns 1902:p.915). Alligator Bluff and the type locality
are in southern Osceola County, Florida, about 16 km south of Lake Kissimmee.
Howell (1932) set the northern limit of distribution as 12.9 km southwest
of Kenansville (Osceola County) where 10 specimens were collected from a
"small colony" in 1929. He also documented a 1927 report of "numerous"
Florida grasshopper sparrows at a location 24 km northwest of Bassinger
(Okeechobee County), referred to two nests found south of Lake Hicpochee
(Hendry County), and stated that Nicholson saw "a number" southeast of
Immokalee (Hendry County), "where they appeared to be breeding".
Nicholson (1936), however, indicated a northern range limit at an
unspecified location 32 km southwest of St. Cloud (Osceola County) with
the population occurring in scattered colonies "sometimes 30 miles apart
to a southern limit at Okeechobee". Howell (1932) and Baynard (1913)
cited two records of an undetermined subspecies occurring in north and
west-central Florida (Alachua and Manatee counties), but their identification
as floridanus is questionable because no specimens north of Kenansville
are extant. On 16 June 1932, Mason (1932) found an unspecified number of
2
sparrows at a location 14.5-24 km south of Fort Drum (Okeechobee
County). In 1935, Schroeder (1956) located "many" birds southwest of
Kenansville, where Sutton (1946) saw "a few pairs" and found a nest with
eggs when he visited the site in 1945. There appear to be no further
records of the subspecies until 1962.
Recent summer records (Stevenson 1978) include one male heard
singing 14 km north of Okeechobee in 1962 and two birds located 1.6 km
south of Brighton (Glades County) in 1963 where one was collected later
that year. In 1968, John Ogden collected one Florida grasshopper sparrow
in atypical habitat near the Everglades National Park (Dade County)
(Stevenson 1968). One singing male was reported "west of Lake Okeechobee"
in 1971 (Ogden 1971). In 1973, one singing male was reported 12.9 km
southwest of Kenansville (Stevenson 1978); a search of the same area in
1974 revealed one pair. From 1974-1979, breeding season searches in
areas of previous sightings failed to locate grasshopper sparrows. The
lack of distributional information precludes a precise delineation
of the historical range, and early accounts provide no documented records
of abundance. Because of an apparent population decline, the Florida
grasshopper sparrow was classified as endangered by the State of Florida
(Kale 1978).
Although specific habitat requirements for floridanus are not known,
preliminary investigations suggest they are atypical of the species (Figure
2). The Florida race inhabits the "stunted growth of Saw palmetto and
Dwarf oaks (Quercus minima) a foot or two high, seemingly preferring this
habitat to the grassy areas usually occupied by other species of
grasshopper sparrow" (Howell 1932). According to Nicholson (1936) the
Florida grasshopper sparrow uses the open spaces "where saw palmettos are
small 10 to 15 inches high and grass is sparse...." Much of this
native prairie has been converted to improved pasture (Davis 1980),
possibly causing the extirpation of the Florida grasshopper sparrow from
some of its former range. Recent observations, however, indicate
that the race may be adapting to these improved pastures (Stevenson, in
Kale 1978).
Florida grasshopper sparrows (Fig. 3) are small, short-tailed birds
about 13 cm long. Dorsally they are much darker than pratensis, being
mostly black and gray (Smith 1963), lightly streaked with brown on the
nape and upper back (Stevenson 1978). Ventrally adults are whitish and
unstreaked with some buff on the throat and breast. The breast is
streaked in juvenile plumage. The stripe over the eye is ochraceous and
the bend of the wing is yellow. The feet are flesh color (Stevenson
1978). No sexual chromatic differences or dimorphism has been reported.
Mearns (1902) described floridanus (based on 3 specimens) as smaller and
darker than other grasshopper sparrows, but with a larger bill and
tarsi. The Florida form is recognized as a distinct subspecies (AOU 1957).
Nests are well arched and constructed on the ground. Usually 4-5
eggs are laid. Nicholson (1936) found nests with eggs and other nests
under construction as early as 23 April. Young in the nest were observed
on 4 June. Breeding activity was again noted on 21 June, indicating a
second brood. Charles Doe found a nest with 4 eggs on 2 April 1927
(Howell 1932). Food eaten during the breeding season (based on the
examination of 10 stomachs) consists primarily of insects and spiders
(69%) and seeds (31%). Grasshoppers, crickets, beetles, weevils and moth
larvae accounted for most of the insects. Sedge seeds constituted most of
the plant material (Howell 1932). Almost no information is available on
the biology of floridanus outside the breeding season. Bailey (1925)
reported finding the sparrow outside its breeding range during the
winter but did not state how he differentiated the birds from migratory
grasshopper sparrows. According to Nicholson (in Smith 1968) hogs,
snakes, and skunks destroy nests and prey upon floridanus.
A survey of the known range of the Florida grasshopper sparrow and
potential habitat outside that range, was conducted during the breeding
season (April-July) from 1980-1984 to gather information on its present
distribution and abundance. Vegetation variables were measured at
territories of male grasshopper sparrows to provide a quantitative
description of habitat for possible use in management of the subspecies.
Surveys conducted in 1984 complemented and filled in gaps in previous
work. In 1984, general abundance and height of plant species were
recorded, along with information on land management practices where birds
were found.
B. PROCEDURES
Surveys were conducted in the dry prairie region of south central
Florida. Most of this habitat is located within the Kissimmee River
Basin and west of Lake Okeechobee in parts of Glades, Hendry, Charlotte
and Desoto counties (Davis 1980).
In Florida, dry prairie grasslands are extensive treeless plains
that often separate fresh water marshes and forested uplands. Seldom
flooded, these grasslands are maintained in early successional stages by
frequent fires. The vegetation is dominated by pineland threeawn
(Aristida stricta), bluestems (Andropogon spp.), carpetgrass (Axanopus
spp.) and paspalum (Paspalum spp.). Saw palmetto (Serenoa repens)
usually occupies large areas in the prairie. Other low woody shrubs
include fetterbush (Lyonia lucida), staggerbush (Lyonia fruticosa) and
ground blueberry (Vaccinium myrsinites). Cabbage palm hammocks,
cypress ponds, and bay heads, consisting of red maple (Acer rubrum), tupelo
(Nyssa biflora), and water oak (Quercus nigra), are interspersed throughout
this prairie region (Hartman 1978).
Bahia grass (Paspalumnotatum), and several species of clover (Trifolium
spp.) have been planted where native plant communities have been
converted to improved cattle pasture. Improved pastures are created and
maintained by mechanical clearing and burning of the native vegetation,
by application of herbicides, lime and fertilizer, and by irrigation
and/or drainage (Milleson et al. 1980). Cattle grazing is the dominant
land use. Due to forest clearing and frequent fires, many areas that
were once open-canopy pineland with an understory of range plants now
resemble saw palmetto prairies (Davis 1943).
Measurements of vegetation variables were made between early May and
mid-June, 1982, at three sites: the Avon Park Wildlife Management Area (WMA)
(Highlands County), Three Lakes WMA (Osceola County), and the Clemon's and
Double Diamond Ranches (Okeechobee County).
All known areas (eight) of former Florida grasshopper sparrow
distribution were located and searched at least twice between 27 May 1980
and 15 June 1984. In addition, nineteen areas that appeared to be
suitable habitat were identified and searched. Surveys were conducted
between sunrise and 1300, by one to three searchers, who walked transects
at 50 m intervals in the habitat, stopping frequently to make visual and
auditory observations. A tape recording of the song of the male
grasshopper sparrow was used to elicit responses from any males in the
area. Where birds were found, information was obtained on the location,
population size and habitat used. Searches were made for Florida
grasshopper sparrows in 24 areas in 1984. These included areas where sparrows
had previously been found, and additional areas with potentially suitable
habitat that had not been searched. In 1984, a total of 11 man-days was
spent walking transects searching for Florida grasshopper sparrows.
Territories were delineated using the flush technique (Wiens 1969).
The center of each territory served as a starting point for two 25 m, randomly
oriented transects. Features of the vegetation composition and structure
were measured at point samples and 1-m2 plots located at 5 m intervals
along each transect. Sampling scheme and calculations were devised by
Whitmore (1981). At each point sample (10 per territory), measurements
included litter depth (cm), height (cm) of the nearest saw palmetto, and
vertical density, which was the total number of vegetation contacts with
a 7 mm diameter metal rod placed vertically into the vegetation. Mean
height was determined by calculating the mean of the highest contact
interval for 10 points; effective height was the highest contact recorded
along the transect. The percentage cover of grasses, forbs, shrubs,
litter, and bare ground was determined from measurements at ten 1 m
subsections of transect adjacent to point samples. Plant species occurrence
was recorded at a 1-m2 quadrat placed adjacent to each point sample. At
one randomly selected 1-m2 quadrat per territory, the number of woody
stems over 20 cm high was recorded. Analysis of variance and Duncan's
Multiple Range Test were used for comparisons of vegetation variables at
territories located on three pastures.
C. RESULTS AND DISCUSSION
Distribution Survey
One hundred and eighty-two Florida grasshopper sparrows (including 10
juveniles) were found at two former locations and 7 new sites during the
period, 1980-1984 (Table 1). Surveys of 6 formerly inhabited sites
(Fig. 4) and 11 areas of potential habitat failed to reveal Florida
grasshopper sparrows. Only marginal habitat, mostly improved pasture,
was found at former sites that are now unoccupied. One new site, one
former site and 108 sparrows were found in 1984. Figures 5-8 show
sparrow locations.
Early records, although vague, indicate that the Florida grasshopper
sparrow was once relatively abundant in south-central Florida. Similar
to other grasshopper sparrows, the Florida race was probably always
sporadic in distributional occurrence. Its isolation from pratensis and
irregular distribution in Florida may be due, in part, to the patchiness
of the native prairie. Despite the location of 7 new breeding sites, the
Florida race remains a rare and relatively unknown bird. Because no
complete surveys for the subspecies have been conducted in the state,
populations in addition to those described in this paper may exist.
Of the 172 adult sparrows found, 119 were males. If each of the
males was mated to a single female, the total population would contain
not quite 250 adults. The known population of 250 breeding birds
represents a minimum estimate of the total population size. It is more
difficult to derive a maximum estimate of Jhe. population size. We have
no doubt that some grasshopper sparrow populations exist in areas that
are virtually inaccessible. Much of the land within the range of the
Florida grasshopper sparrow is contained in a few large, private
ranches. Few roads cross this area, and aerial photographs are of little
use in distinguishing areas of native dry prairie from other pastures
and fields. The roads that we have driven in grasshopper sparrow range have
few areas of potential sparrow habitat along them---certainly less than
20% of the road frontage is native dry prairie, and not all of that has
been burned recently enough to provide suitable habitat for grasshopper
sparrows.
It may be possible to use Landsat data to locate areas of potential
grasshopper sparrow habitat in more remote areas. Landsat records, on
computer tape, reflectance values in different portions of the visible
and infra-red spectra for every spot on the earth's surface every 14-18 days.
Theoretically, it is possible to measure the reflectance values for known
grasshopper sparrow habitat and let the computer locate other areas with
similar values.
A helicopter might improve access to and facilitate surveys of more
remote areas (see Delany et al. 1981).
Habitat Use
In general, grasshopper sparrows were located on treeless, relatively
poorly drained sites that have been burned frequently. A total of 86
plant species occurred in 320 m2 plots located on 32 territories. A
dominant plant in this prairie grassland community was saw palmetto,
which occurred in 34% of the plots. Common shrubs included pawpaw
(Asimina spp.), dwarf oak (Quercus minima), gopher apple (Licania
michauxii), and St. John's Wort (Hypericum fasciculatum). The grass and
herbaceous ground layer was rich in species, being dominated by pineland
threeawn (Aristida stricta), bluestems (Andropogon spp.) and flat-topped
goldenrod (Euthamia minor). In wetter areas of lower elevation, the
herbaceous layer included beak rushes (Rhynchospora spp.), pipewort
(Eriocaulon spp.), and yellow-eyed grass (Xyris spp.). Slash pine (Pinus
elliottii) plantations occurred near most territories, and cypress domes
were located near some territories in wetter areas. The variety of plant
species increased with the elapsed time since the last burn. Forty-two
species were found in an area 3 months after a burn (60 m2 plots) and 60
were recorded from the same number of plots in an adjacent area sampled 2
years after a fire. A list of plant species is presented in Table 2.
Most structural features of Florida grasshopper sparrow territories
varied considerably (Table 3). The habitat containing territories ranged
from thick, low palmetto scrub to grass pastures with a sparse or patchy
cover of saw palmetto. Much of this variation was related to the degree
of pasture improvement. On areas now occupied by grasshopper sparrows,
prescribed burning is conducted by ranchers during the winter (November-
January) at 2-3 year intervals. Other methods employed to manage
pastures containing territories ranged from occasional chopping to
liming, fertilizing and planting bahia grass. Cattle grazing, at a rate
of 1 animal unit per 8 ha, occurred on all sites occupied by sparrows.
Territories in three pastures, which ranged in size from 58 ha to
465 ha, were at different stages of regeneration following prescribed
fire. Differences (P < 0.05) among territories in percentage grass
cover, shrub cover, vertical density and height corresponded with a
general post-burn increase in plant material (Table 4). A concurrent
increase (P < 0.05) in the percentage of litter cover, as well as litter
depth, followed a similar pattern.
The structural characteristics of Florida grasshopper sparrow
habitat that differ most from those reported for the eastern race (Wiens
1969, Whitmore 1981) are the percentage of shrub cover (including saw
palmetto) and bare ground. Whitmore (1981), using similar methods,
reported only 0.7% shrub cover and 21.9% bare ground on grasshopper
sparrow territories in West Virginia whereas floridanus habitat was
characterized by values of 19.2% and 36.2%, respectively. Further,
habitat used by floridanus had much lower values than pratensis for
vertical density, vegetation height, forb cover, litter cover, and litter
depth. The proportion of grass cover and the dominance of bunch grass
species, rather than sod-forming types, was similar to grasshopper
sparrow habitat reported in other studies (Wiens 1969, Whitmore 1981).
The occupied areas studied in Florida exhibited a predominance of
saw palmetto, shrubs and dwarfed trees. Yet at most areas used by
floridanus, vegetation height was lower than in the adjacent habitat. It
is possible that the local hydrology (i.e., poor drainage) and frequent
fires keep these sites from developing towards a successional stage
unusable by grasshopper sparrows. Adjacent areas of taller vegetation
where grasshopper sparrows were not found were usually occupied by
Bachman's sparrows (Aimophila aestivalis). Sparrow densities appeared to
be lower in areas that were not recently (within 3 years) burned.
D. CONCLUSIONS AND RECOMMENDATIONS
1. Status of Species
In the early 1900's, the population of Florida grasshopper sparrows
was reportedly large and widespread in Florida; however, surveys between
1980 and 1984 revealed only 182 sparrows at nine sites. The sparrow was
found at only two of its former locations, suggesting a reduction in both
abundance and occupied range. An even greater range contraction would be
indicated if early records in Manatee and Alachua counties were floridanus
rather than pratensis. Alteration and loss of habitat due to range
management is the greatest threat to the Florida grasshopper sparrow.
Because of its meager abundance, restricted distribution, and loss of
habitat consideration of the following seems appropriate:
a. Present. or threatened destruction, modification, or curtailment of
its habitat or range
The principle threat to floridanus is habitat loss or degredation
resulting from pasture improvement. The Florida grasshopper sparrow
apparently can tolerate some alteration in vegetation composition and
structure induced by range management, as evidenced by its occurrence in
some improved pastures. Sparrows were found in improved pastures that
were in various stages of mismanagement, i.e., where native vegetation
was beginning to invade. It is unlikely, however, that the sparrow can
adapt to conditions that result from intensive pasture management, which
removes all shrubs and saw palmetto. Grasshopper sparrows were found
Bachman's sparrows (Aimophila aestivalis). Sparrow densities appeared to
be lower in areas that were not recently (within 3 years) burned.
D. CONCLUSIONS AND RECOMMENDATIONS
1. Status of Species
In the early 1900's, the population of Florida grasshopper sparrows
was reportedly large and widespread in Florida; however, surveys between
1980 and 1984 revealed only 182 sparrows at nine sites. The sparrow was
found at only two of its former locations, suggesting a reduction in both
abundance and occupied range. An even greater range contraction would be
indicated if early records in Manatee and Alachua counties were floridanus
rather than pratensis. Alteration and loss of habitat due to range
management is the greatest threat to the Florida grasshopper sparrow.
Because of its meager abundance, restricted distribution, and loss of
habitat consideration of the following seems appropriate:
a. Present. or threatened destruction, modification, or curtailment of
its habitat or range
The principle threat to floridanus is habitat loss or degredation
resulting from pasture improvement. The Florida grasshopper sparrow
apparently can tolerate some alteration in vegetation composition and
structure induced by range management, as evidenced by its occurrence in
some improved pastures. Sparrows were found in improved pastures that
were in various stages of mismanagement, i.e., where native vegetation
was beginning to invade. It is unlikely, however, that the sparrow can
adapt to conditions that result from intensive pasture management, which
removes all shrubs and saw palmetto. Grasshopper sparrows were found
only on areas that had at least some saw palmetto, shrubs and bunch
grasses. Nest sites are reportedly located on the ground beneath bushes
or tall clumps of grass (Nicholson 1936), features that would not exist
in the most improved pastures.
Six of the 8 previously known populations of the Florida grasshopper
sparrow may have been extirpated as a result of range management. The 7
new localities found since 1980 and two former locations are currently
managed for cattle (Table 5). For the most part, this does not appear to
have adversely affected these populations because prescribed fire improves
the habitat for the Florida grasshopper sparrow by maintaining the
prairie grassland community at an early successional stage. There is a
possibility, however, that range management on occupied sites may become
more or even less intensive, rendering them unsuitable for grasshopper
sparrows. More intensive management (removing saw palmetto and planting
grass) would eliminate nesting sites. The exclusion of fire and other
management practices would allow vegetation to reach a successional stage
unusable by the sparrow. Most landowners and managers are not aware of
the sparrows existence or needs. Further, the Florida grasshopper
sparrow is usually not considered when habitat management decisions are
made for public lands. Present land use trends indicate a continued loss
of habitat for floridanus (Table 5).
b. Utilization for commercial, sporting, scientific, or educational
purposes at a level that detrimentally affects it
There is no indication that any of these factors have in the past
had any significant impact on the Florida grasshopper sparrow. There is,
however, potential for adverse impact if isolated pairs are collected or
scientific collection is conducted at locations where numbers are small.
c. Disease or predation
There is no evidence that disease or predation constitute serious
threats to the continued survival of floridanus.
d. Absence of regulatory mechanisms (State of Federal) adequate to
prevent the decline of the species or degradation of its habitat
There are no adequate regulatory mechanisms to assure protection of
prairie grassland habitat in private ownership. The Avon Park Bombing
Range, Three Lakes, and Fisheating Creek Wildlife Management Areas
contain suitable habitat and are under some State or Federal control.
The Florida Game and Fresh Water Fish Commission has authority to
prohibit or regulate the collection of Florida grasshopper sparrows.
However, collecting is not considered to represent a significant threat
to floridanus.
e. Other natural or man-made factors affecting its continued existence
Military activity and methods of range management are discussed below.
2. Essential Habitat
Locations of Florida grasshopper sparrows are shown in figures 4-8
and described in table 1. Unoccupied sites that appear to be suitable
habitat are located in: Glades County, on the Lykes Brothers Refuge
(T40S, R30E Sec. 25,30), Desoto County, on the Montogmery Ranch (T39S,
R27E Sec. 15,24), and Osceola County along the Florida Turnpike (T28S,
R31E Sec. 22, 23, 25, 26 T29S, R32E Sec. 30,31).
A low, but sparse growth of saw palmetto, woody shrubs, and bunch
grass is apparently needed for nesting. Dense vegetation and accumulated
litter would probably preclude effective foraging by the sparrow. During
the breeding season the bird's food consists of insects, spiders and
seeds. No information is available on minimum area required, winter
habitat and diet, impact of migrant grasshopper sparrows, and interspecific
competition with Bachman's sparrows.
Current or planned activities which may affect the quality of the
habitat are summarized in Table 5.
3. Management and Recovery
Alteration and loss of habitat due to range management is the
greatest threat to the Florida grasshopper sparrow. Ranchers and
managers of public lands whose pastures are inhabited by this sparrow, as
well as those with pastures close to known colonies, should be encouraged
to maintain a low (30-70 cm), but sparse, growth of palmettos and woody
shrubs. Management of this habitat by prescribed burning of small areas
(50-100 ha) on a 2 year rotation may be helpful. Cattle grazing at
current levels, 1 animal unit per 8 ha, does not appear to be detrimental.
Known populations should be monitored and an effort should be made to
locate new colonies for protection and management.
The following information is relevant to the problem of how best to
manage Florida grasshopper sparrow populations. In 1981-82, only 4 adult
grasshopper sparrows were found at Three Lakes Wildlife Management Area,
Osceola Co. Many of the pastures at Three Lakes WMA were burned in the
winter of 1983-84, and 37 adult grasshopper sparrows were found there in
1984 (Table 1). At the site owned by the Latt Maxcy Corp. in Okeechobee
Co., no sparrows were found in 1982, but 32 were found in 1984. This
pasture is burned every 3 years, and was last burned in the winter of
1982-83. In the summer of 1982, when no sparrows were present, it had
been 2-1/2 years since the pasture was last burned. In one pasture on
the Adams Ranch, only one grasshopper sparrow was found in 1982, but
eight were found in 1984. This pasture is burned every 2 or 3 years, and
was last burned in the winter of 1982-83. It is evident from these
figures that the burning greatly improved the quality of the pastures for
grasshopper sparrows.
In contrast to the above locations are pastures along Durden Road in
Avon Park WMA. Eight grasshopper sparrows were found along Durden Road
in 1982, but only one could be found in 1984. The pastures had not been
burned in the intervening years, and the vegetation was very dense, with
little bare ground. As a general rule then, it appears that pastures
should be burned every other winter in order to support stable grasshopper
sparrow populations, but further research is needed to substantiate this
conclusion.
Grasshopper sparrows were found in 1984 in two pastures that had
been chopped in the previous few months. Chopping greatly reduces the
amount of vegetative cover and may slow the spread of shrubs. In those
respects, chopping may improve the quality of a pasture for grasshopper
sparrows and be a useful alternative to burning in some cases. In
general, however, chopping is often a prelude to other, more intensive
forms of land management, possibly signalling the local demise of Florida
grasshopper sparrows.
Considerable information is needed before the Florida grasshopper
sparrow can be properly managed and the effects of management actions
assessed. Essential information is discussed under research needs
(page 18).
4. Taxonomy
Grasshopper sparrows (Ammodramus savannarum) are typical sparrows,
most recently placed in the subfamily Emberizinae, family Emberizidae,
order Passeriformes (Paynter and Storer 1970, American Ornithologists'
Union 1983). Grasshopper sparrows are common breeders throughout much of
the continental United States, ranging from southern Canada south to
Georgia, Texas, and California. Additional populations are locally
distributed from Mexico south to Colombia and in the West Indies.
Paynter and Storer (1970) recognized 11 subspecies of Ammodramus
savannarum. Ammodramus savannarum floridanus, a well-marked subspecies,
was first described by E.A. Mearns (1902) on the basis of one male and
two females collected in 1901 in southern Osceola Co., Florida.
A. s. floridanus has been universally accepted as a valid subspecies
(American Ornithologists' Union 1910, 1931, 1957; Hellmayr 1938; Paynter
and Storer 1970).
5. Impact of Federal Activity
It is not known if target areas on the U.S. Air Force, Avon Park
Bombing Range (APBR) contain Florida grasshopper sparrows. Fire
forms of land management, possibly signalling the local demise of Florida
grasshopper sparrows.
Considerable information is needed before the Florida grasshopper
sparrow can be properly managed and the effects of management actions
assessed. Essential information is discussed under research needs
(page 18).
4. Taxonomy
Grasshopper sparrows (Ammodramus savannarum) are typical sparrows,
most recently placed in the subfamily Emberizinae, family Emberizidae,
order Passeriformes (Paynter and Storer 1970, American Ornithologists'
Union 1983). Grasshopper sparrows are common breeders throughout much of
the continental United States, ranging from southern Canada south to
Georgia, Texas, and California. Additional populations are locally
distributed from Mexico south to Colombia and in the West Indies.
Paynter and Storer (1970) recognized 11 subspecies of Ammodramus
savannarum. Ammodramus savannarum floridanus, a well-marked subspecies,
was first described by E.A. Mearns (1902) on the basis of one male and
two females collected in 1901 in southern Osceola Co., Florida.
A. s. floridanus has been universally accepted as a valid subspecies
(American Ornithologists' Union 1910, 1931, 1957; Hellmayr 1938; Paynter
and Storer 1970).
5. Impact of Federal Activity
It is not known if target areas on the U.S. Air Force, Avon Park
Bombing Range (APBR) contain Florida grasshopper sparrows. Fire
spreading from target areas as a result of exploding ordinance could,
however, threaten sparrows on adjacent areas. There would be immediate
adverse impact if targets were moved to locations where Florida grasshopper
sparrows occur. Pastures on the APBR are leased for cattle grazing. The
discontinuation of range management or further improvement of pastures
would both adversely affect the sparrow. Reforestation of occupied sites
would be detrimental to floridanus.
6. Research Needs
To determine limiting factors for floridanus and properly manage
habitat, needed research includes the following:
a. Information on habitat correlates of abundance and changes in
habitat use relative to fire and plant succession. Habitat use
outside the nesting season should be determined.
b. Biological studies should be conducted to determine reproductive
success, nesting, dispersal of fledglings, predation, survival, and
food habits.
c. Additional surveys should be conducted to more thoroughly determine
current distribution and abundance. We recommend using Landsat data
to locate search areas.
LITERATURE CITED
American Ornithologists' Union. 1910. Check-list of North American
Birds, 3rd edition. American Ornithologists' Union, New York.
1931. Check-list of North American
birds, 4th edition. American Ornithologists' Union, Lancaster,
Pennsylvania.
1957. Check-list of North American
birds, 5th edition. American Ornithologists' Union, Baltimore.
1983. Check-list of North American
birds, 6th edition. American Ornithologists' Union, Washington, D.C.
Bailey, H.H. 1925. The Birds of Florida. The Williams and Wilkins Co.
Baltimore, MD. pp.102.
Baynard, O.E. 1913. Breeding birds of Alachua County, Florida. Auk
30:240-247.
Davis, J.H;, Jr. 1943. The natural features of southern Florida.
Fla. Dep. of Conserv. Geol. Surv. Bull. 25. 311pp.
Davis, J.H. 1980. General map of natural vegetation of Florida.
Univ. Florida Agric. Exp. Stn. Circ. S-178.
Delany, M.F., W.P. Leenhouts, B. Sauselein, H.W. Kale, II. 1981. The
1980 Dusky seaside sparrow survey. Fla. Field Natur. 9:64-67.
Hartman, B. 1978. Description of major terrestrial and wetland habitats
of Florida. Pages xii-xv in H.W. Kale, II, ed. Rare and endangered
biota of Florida, Vol. 2-Birds. Univ. Florida Presses, Gainesville.
Hellmayr, C.E. 1938. Catalogue of Birds of the Adjacent Islands.
Part XI. Field Museum of Natural History, Zoological Series,
Vol. XIII, Part XI.
Howell, A.H. 1932. Florida bird life. Coward-McCann, New York, N.Y.
579 pp.
Kale, H.W., II. 1978. Rare and endangered biota of Florida, Vol. 2-
Birds. Univ. Florida Presses, Gainesville. 121 pp.
Mason, C.R. 1932. Notes from correspondents. Fla. Nat. 6:15.
Mearns, E.A. 1902. Descriptions of three new birds from the southern
United States. Proc. U.S. Nat. Mus. 24:915-926.
Milleson, J.F., R.L. Goodrick, and J.A. Van Arman. 1980. Plant
communities of the Kissimmee River Valley. South Fla. Water
Manage. Dist. Tech. Pub. 80-7. 42 pp.
Nicholson, W.H. 1936. Notes on the habits of the Florida grasshopper
sparrow. Auk 53:318-319.
Ogden, J.C. 1971. Florida region. Amer. Birds 25:280-281.
Paynter, R.A., Jr., and R.W. Storer. 1970. Check-list of Birds of the
World. Vol. XIII. Museum of Comparative Zoology, Cambridge Mass.
Schroeder, H.H. 1956. The Florida grasshopper sparrow. Audubon Mag.
58:70-71,92.
Smith, R.L. 1963. Some ecological notes on the Grasshopper sparrow.
Wilson Bull. 75:159-165.
Smith, R.L. 1968. Grasshopper Sparrow. Pp.725-745 in O.L. Austin, Jr., ed.
Life Histories of North American Cardinals, Grosbeaks, Buntings,
Towhees, Finches, Sparrows, and Allies. Part 2. United States
National Museum, Bulletin 237, part 2.
20
Stevenson, H.M. 1968. Florida region. Audubon Field Notes. 22:599-602.
S 1978. Endangered Florida grasshopper sparrow. Pages
15-16 in H.W. Kale, II, ed. Rare and endangered biota of Florida,
Vol. 2-Birds. Univ. Florida Presses, Gainesville.
Sutton, G.M. 1946. A baby Florida sandhill crane. Auk 63:100-101.
Whitmore, R.C. 1981. Structural characteristics of grasshopper sparrow
habitat. J. Wildl. Manage. 45:811-814.
Wiens, J.A. 1969. An approach to the study of ecological relationships
among grassland birds. Ornithol. Monogr. 8. 93 pp.
ACKNOWLEDGEMENTS
Research conducted between 1981-1982 was supported by the Federal
Aid to Endangered Species Program, Florida Endangered Species Project E-
1. Surveys during 1984 were supported by Cooperative Agreement No. 14-
16-0009-1544, Research Work Order 14, funded by the United States Fish
and Wildlife Service, Jacksonville Endangered Species Office through the
Florida Cooperative Fish and Wildlife Research Unit. We are grateful to
M. Bentzien and H.F. Percival who made possible the completion of this
study. R.L. Barker and S.A. Martin participated in the survey and assisted
in locating survey areas. R.P. Wunderlin assisted with plant identification.
C.L. Abercrombie provided statistical advice. J. Bart, T.C. Hines,
D.S. Maehr, and L.E. Williams, Jr. reviewed earlier drafts of this
manuscript and provided many useful suggestions. Special appreciation is
extended to A.L. Adams, III, P. Clemons, D.W. Delargey, W.C. Funk,
C.E. Lough, and P.T. Wilson, who provided access to their properties.
H.M. Stevenson and R. McCracken contributed to this report. V.L. Sims
key-punched habitat data. T.L. Crown typed this and previous drafts of
this report. The senior author thanks his family for their patience and
encouragement during this project.
Figure 1. Range of the grasshopper sparrow (from Field Guide
to the Birds of North America, National Geographic
Society).
Figure 2. Florida grasshopper sparrow habitat.
Figure 3. Florida grasshopper sparrow.
I..
*~ 4,
-- -- C
'SW
-91
N
0
)---- t ,,
FORMER SITE, OCCUPIED
O FORMER SITE, UNOCCUPIED
RECENT SITE, 1980-1982
50
Figure 4. Florida grasshopper sparrow locations, 1984.
Figure 5.
Florida grasshopper sparrow locations in Osceola County.
co
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Table 2. Frequency of occurrence for plants at 32 Florida grasshopper
sparrow territories (320 m2 plots), 15 April to 15 June 1982.
Species Percent Frequency
Serenoa repens (saw palmetto) 33.8
Fimbristylis autumnalis (Fimbristylis) 5.9
Fimbristylis puberula (Fimbristylis) 13.8
Fuirena sciroidea (umbrella grass) 4.1
Rhynchospora fasiculata (beak rush) 12.5
Rhynchospora microcarpa (beak rush) 13.4
Rhynchospora spp. (beak rush) 4.1
Lachnocaulon minus (bog-buttons) 49.4
Lachnanthes caroliniana (bloodroot) 4.7
Aletris aurea (yellow star-grass) 4.0
Andropogon capillipes (chaulky bluestem) 39.1
Andropogon virginicus (broomsedge) 15.0
Aristida stricta (wiregrass) 76.9
Axanopus affinis (common carpetgrass) 8.4
Ctenium aromaticum (toothachegrass) 8.4
Dicanthelium acuminatum (Dicanthelium) 48.4
Panicum absicissum (cutthroatgrass) 6.3
Paspalum setaceum (thin Paspalum) 16.6
Setaria geniculata (knotroot foxtail) 4.1
Sorghastrum secundum (lopsided indiangrass) 8.4
Xyris brevifolia (yellow-eyed grass) 30.0
Asimina reticulata (pawpaw) 15.6
Table 2. (continued)
Species Percent Frequency
Carphephorus paniculatus (deer-tongue) 12.5
Erigeron vernus (robin's plantain) 16.6
Eupatorium recurvans (dog fennel) 24.4
Euthamia minor (flat-topped goldenrod) 26.3
Heterotheca graminifolia (grass-leaved golden-aster) 18.1
Liatris tenuifolia (blazing-star) 4.4
Pterocaulon virgatum (blackroot) 18.4
Trilisa odoratissima (vanilla-plant) 9.7
Licania michauxii (gopher apple) 19.7
Gaylussacia dumosa (dwarf huckleberry) 12.8
Lyonia fruticosa staggerbushh) 10.6
Vaccinium myrsinites (ground blueberry) 8.1
Stillingia sylvatica (queen's delight) 15.0
Quercus minima (dwarf oak) 77.8
Hypericum fasciculatum (St. John's-wort) 22.0
Hypericum myrtifolium (St. John's-wort) 9.1
Rhexia cubensis (meadow beauty) 6.9
Rhexia nuttallii (meadow beauty) 16.3
Ludwiga maritima (Ludwiga) 4.4
Polygala regelii (Polygala) 5.0
Polygonella gracilis (wireweed) 9.1
Gratiola hispida (Gratiola) 5.0
Table 3. Structural characteristics of Florida grasshopper sparrow territories
(N = 32) in Osceola, Okeechobee, and Highlands counties, 15 May-15 June 1981-82.
Variable x SD Range
Grass cover (%)
Shrub cover (%)
Forb cover (%)
Litter cover (%)
Bare ground (%)
Number of stems/m2
Litter depth (cm)
Palmetto height (cm)
Vertical density: contacts/transect
Mean vegetation height (cm)
Effective vegetation height (cm)
25.5
19.2
4.5
14.4
36.2
30.7
0.7
57.3
66.9
27.8
46.9
18.2
7.8
4.5
8.9
19.5
23.5
0.6
10.9
35.1
6.8
12.0
5.1-69.3
0.0-33.9
0.5-21.0
2.4-34.4
4.9-67.7
0.0-87.0
0.0-2.7
37.1-80.1
10.0-145.0
9.0-39.0
30.0-70.0
--
Table 4. Comparison of the vegetative structure of 24 Florida grasshopper
sparrow territories on three pastures, Avon Park Wildlife Management Area,
1982. Means with the same letter within a row are not significantly
different (P = 0.05).
Means (SD)
Pasture 1: Pasture 2: Pasture 3:
3 months 1 year 2 years
post-burn post-burn post-burn
Variable (N=60 plots) (N=120 plots) (N=60 plots)
Grass cover (%)
Shrub cover (%)
Forb cover (%)
Litter cover (%)
Bare ground (%)
Number of stems/m2
Litter depth (cm)
Palmetto height (cm)
Vertical density:
contacts/transect
Mean vegetation
height (cm)
Effective vegetation
height (cm)
8.7a
(2.4)
24.3a
(6.9)
3.4a
(2.9)
3.8a
(0.7)
59.8a
(6.6)
27.3a
(29.8)
0.2a
(0.3)
58.8a
(10.3)
33.8a
(11.2)
22.7a
(4.2)
40.0a
(12.6)
19.8b
(6.2)
19.5ab
(5.7)
3.0a
(3.1)
13.8b
(8.2)
43.3b
(13.5)
30.8a
(22.2)
0.7b
(0.5)
60.2a
(13.6)
70.3b
(21.3)
30.9b
(4.4)
50.8b
(12.4)
52.2c
(9.1)
14.3b
(5.8)
2.9a
(1.8)
20.5c
(6.8)
10.2c
(4.4)
30.2a
(21.9)
1.4c
(0.7)
55.0b
(3.8)
116.7c
(21.0)
33.8b
(4.1)
53.3b
(8.2)
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