THE ECOLOGY AND VOCALIZATIONS OF SCOTT'S SEASIDE SPARROWS
(Ammodramus maritimus peninsula)
MARY VICTORIA MCDONALD
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
Mary Victoria McDonald
Since this dissertation is a formal report of my doctoral research,
it would be inappropriate for me to describe all of my ideas and my
feelings over the years--false starts, hunches that paid off, my
occasional discouragement, confusion, and elation, and even the kinship
I felt working with "my" birds on "my" marsh. But these elements were
inextricably woven into my study. What saw me through was not just my
scientific approaches to interesting ornithological questions, but also
determination and good luck, and, most of all, invaluable help from
friends and advisors.
Dr. John William Hardy, my major advisor, steadfastly supported and
guided me through the years. His timely reviews of my work and my
requests for recommendations, his just criticisms, and his flexibility
in allowing me to work independently all significantly contributed to
the success of my graduate career. My other graduate committee members,
Drs. Pierce Brodkorb, John H. Kaufmann, Peter Feinsinger, and Thomas J.
Walker, thoughtfully and generously advised me throughout my project.
Many other faculty members in the Department of Zoology also helped me
I am fortunate to have had valuable suggestions from three
ornithologists very knowledgeable about seaside sparrows--Herbert W.
Kale II, Jon S. Greenlaw, and William Post. William Post patiently
helped me get started in my field work at Cedar Key and allowed me to
incorporate some of his unpublished reproductive data and banding
records with my data, as presented in Chapter II of this dissertation.
The Department of Zoology generously supported me with teaching and
research assistantships, equipment, and vehicle use. The Florida State
Museum Bioacoustics Laboratory provided sound analysis equipment and
work space. Other financial support was provided with grants from
several sources: Sigma Xi Grants-In-Aid of Research (1982 and 1983),
Frank M. Chapman Memorial Fund Awards (1983 and 1984), Eastern Bird
Banding Association Research Award (1984), and Van Tyne Memorial Fund
Grant of the American Ornithologists' Union (1984).
John David Wood, Sr., graciously permitted me to conduct my project
on his property near Cedar Key, Florida. The Florida Department of
Natural Resources rangers of the Waccasassa Bay Station near Cedar Key
helped make my sometimes uncomfortable, and always wet and muddy field
work more bearable. Two occasional field assistants, Janine Russ and
David Specht, were genial and as well as adept companions. Thomas A.
Webber also helped me in the field with photography and sound recording.
Many, many other people helped me indirectly over the years. The
support of my parents, Carlyle A. McDonald and Margaret L. McDonald, was
invaluable. And likewise invaluable were the advice and support of many
fellow graduate students. Thomas A. Webber and Linda S. Fink deserve
special thanks--their suggestions, thoughtful and significant criticisms
of my work, and, most of all, their supportive friendships have been
essential parts of my graduate work and life.
TABLE OF CONTENTS
ACKNOWLEDGEMENTS . . . . . iii
LIST OF TABLES . . . . . . vii
LIST OF FIGURES . . . . . . viii
ABSTRACT . . . . . . x
I GENERAL INTRODUCTION . . . . 1
II NATURAL HISTORY AND BEHAVIORAL ECOLOGY OF SCOTT'S
SEASIDE SPARROWS: STUDY TECHNIQUES AND RESULTS . 2
Taxonomy and Morphology . . . . 2
Project History and General Methods . . . 4
Study Site . . . . . 6
General Description . . . . 6
Weather . . . . . 7
Marsh Fauna . . . . . 8
Vertebrate fauna . . . . 8
Invertebrate fauna and seaside sparrow foraging 9
Marsh Flora . . . . . 10
Size and Demarcation of Study Sites . . 11
Reproduction and Reproductive Behavior . . .. 11
Overview of Annual Cycle . . . 11
Annual Cycle of Reproductive Behavior . . 15
Territorial establishment and mating . 15
Nests, eggs, and early development . ... 18
Nesting behavior . . . . 20
Post-breeding behavior . . 22
Productivity, Survival and Reproductive Success . 23
Territories and Territorial Behavior . . 29
Definition and Methods of Determining Territories 29
Description of Territories at Cedar Key . . 29
Territorial Behavior . ............... 30
Reactions to Other Species of Birds and to Humans 32
Discussion of Seaside Sparrow Territoriality . 34
Territory types and variation . . 34
Territory quality and space use . . 35
Extension of territory definition and function 36
III VOCALIZATIONS OF SCOTT'S SEASIDE SPARROWS . . 40
Introduction . . . . . 40
General Methods of Data Collection and Analysis . .. 41
Coverage . . ... . . 41
Sample Size and General Observation Methods . 42
General Analysis of Notes and Recordings . 43
Results and Discussion of Calls and Song . ... 45
Description and Use of Vocalizations . .. 45
Calls of Scott's seaside sparrows . . 47
Primary song . . . 73
Subsong . .o. . . . 79
Countersinging and Repertoire Use .. . . 79
Introduction and comments . . .. 79
Methods of investigating repertoires . .. 82
Results and discussion of repertoire use . 83
Flight Songs: Description and Comparison to
Perch Songs . . . . 84
Description . . . . . 84
Methods of investigating flight song activity 85
Results of singing activity analysis . 87
Discussion of flight songs . .. . 88
IV FUNCTION OF SONG IN SCOTT'S SEASIDE SPARROWS .. . 98
Introduction . ... . . . ... 98
Methods . . . . . 101
Experimental Design . . . . 101
Muting Procedure . . . . .. 106
Statistical Analysis . . . . 108
Results . .. . . . . 109
Voice and Post-Operative Recovery . . .. 109
Mate Attraction and Retention . . 110
Territory Establishment, Retention, and Size Change 119
Behavioral Changes of Muted Birds . . 120
Reaction to Playback . . . . 129
Voice Recovery and Subsequent Behavior .. . 130
Discussion . . . . . 130
V CONCLUSIONS . . . . . 135
REFERENCES . . .. . . . .. 136
BIOGRAPHICAL SKETCH . . . . . 145
LIST OF TABLES
Summary profile of territoriality and reproduction
of Scott's seaside sparrows at Cedar Key, Florida,
1979-1984 . . . . .
Vocalizations and behaviors measured during time
budget observations . . . .
Vocalizations of Scott's seaside sparrows . .
Characteristics of solo primary singing and
countersinging of 30 mated male Scott's seaside
sparrows during April and May . . .
Experimental design of muting experiments . .
During songless comparison of territory ownership
and size changes for the Mid-Season mutings .
"After song regained" comparison of territory
ownership and size changes for the
Mid-Season mutings . . . .
Behavior changes for individuals, from "Before"
to "During" muted . . . .
Behavior differences comparing Muted, Sham, and
Undisturbed groups . . . .
Sexual selection related to two main song types .
LIST OF FIGURES
Breeding chronology of seaside sparrows at
Cedar Key, Florida, 1979-1984 . .
(A) Audiospectrogram of Tuck call (short notes
8 kHz), and 1 interspersed Tsip call (vertical
(B) Audiospectrogram of Tsip call.
(C) Audiospectrogram of Seeep note . .
(A) Audiospectrogram of male Primary song and
concurrent female Seeep note.
(B) Audiospectrogram of Tchi call . .
Audiospectrogram of Whinny vocalization
Audiospectrogram of Zuck calls . .
Audiospectrogram of Scree calls .
Audiospectrogram of Begging calls from
two nestlings, individuals A and B .
Audiospectrogram of Primary song .
Audiospectrogram of Subsong . .
Audiospectrograms of Countersinging from
individuals A and B . . .
Audiospectrogram of Flight song .
Relationship between time of day and the
of Flight songs/Perch singing . .
* o o
Relationship between wind velocity and the ratio
of Flight songs/Perch singing . . .
Relationship between temperature and the ratio
of Flight songs/Perch singing . . .
Number of Flight songs recorded in early 1983
given by birds of designated mated categories
Audiospectrogram of song of bird ABOR recorded
3 days prior to muting . . ..
Audiospectrogram of "songs" of muted bird ABOR
recorded 5 days after muting . . .
Relative abilities of Muted versus Sham-Operated
and Undisturbed males to attract and retain
females 1983 and 1984 . . . .
Behavioral changes of 21 muted birds Before and
During their songless periods . . .
Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
THE ECOLOGY AND VOCALIZATIONS OF SCOTT'S SEASIDE SPARROWS
Ammodramus maritimus peninsula
Mary Victoria McDonald
Chairman: Dr. John William Hardy
Major Department: Zoology
I studied the ecology and vocalizations of Scott's seaside sparrows
(Ammodramus maritimus peninsula) in a Florida salt marsh from
1981-1985. I observed the behavior, vocalizations and reproductive
efforts of 20-30 pairs each year on the 30 ha gridded study site. These
monogamous birds defended all-purpose territories about 1,750 m2 in size
with song and short-distance agonistic behaviors. A high proportion
of males (0.79) returned each year to their previous territories, and
half (0.50) of these remated with their previous year's mates. Although
females initiated about 3.7 clutches of 3 eggs each season, productivity
was low (0.67 fledglings/female/year), because predators destroyed about
80% of the nests. Nevertheless, population numbers remained stable over
the years 1979-1985. The birds' vocal repertoires consisted of a
primary song, three modified primary songs (whispering song, flight
song, and subsong), and 10 calls. Only males sang; they had a song
type repertoire of 2-3 songs. I experimentally investigated the
function of song during the breeding seasons of 1983-1985 by temporarily
muting male birds in the field. I muted birds by rupturing the
interclavicular air sac. Birds remained songless for about 2 weeks but
could give all of their normal calls during this time. I administered
two rounds of mutings, each preceded and followed by time budget,
playback, and other observations on 3 treatment groups: Muted,
Sham-Operated, and Undisturbed birds. The Early muting round tested for
mate and territory acquisition. These Muted birds remained mateless
until they regained their voices; most eventually attracted a mate.
Muted birds acquired territories later than Sham-Operated and
Undisturbed birds. The Mid-Season muting round tested for mate and for
territory retention, and changes in behavior. All Muted birds lost their
mates; a few attracted new mates when they regained their singing
ability. Their territories either shrank or were lost, but new
territories were established (or the original re-expanded) when singing
ability returned. The intensity of close-range aggressive behaviors was
significantly greater for Muted birds than for Sham-Operated and
Undisturbed birds. There were no discernible differences between
Sham-Operated and Undisturbed birds for any of the attributes measured.
I studied the ecology and vocalizations of Scott's seaside sparrows
(Ammodramus maritimus peninsula) on a salt marsh near Cedar Key,
Florida, for 5 years. William Post had studied the reproductive ecology
of this population from 1979-1980. In early 1981, I began my
investigations and continued my study through the spring of 1965. The
principal objective of my research was to determine the function of the
vocal repertoire of these birds. During the course of my field work,
however, I observed many aspects of their biology and also collected
reproductive and non-vocal behavioral data.
This dissertation summarizes both my observational and experimental
investigations of the study population. Chapter II is an overview of
the project history, study site, general methods, and the birds and
their biology. Chapter III describes the vocal repertoire and discusses
the probable function of these vocalizations. Chapter IV summarizes the
experiments I conducted in 1983 and 1984, whereby I determined the
function of song in Scott's seaside sparrows.
The information presented throughout most of this dissertation
portrays the behavior of birds I observed and tape recorded with a
minimum of disturbance. The exception, of course, is that Chapter IV
presents results of manipulative experiments. Thus I sometimes make the
distinction between "normal" and "experimentally manipulated" birds.
NATURAL HISTORY AND BEHAVIORAL ECOLOGY OF SCOTT'S SEASIDE SPARROWS:
STUDY TECHNIQUES AND RESULTS
Taxonomy and Morphology
Seaside sparrows (Ammodramus maritimus) belong to the "grassland
group" of Emberizine finches (subfamily Emberizinae), which also
includes the genera Ammospiza and Passerculus. The nominate form (A. m.
maritimus) was originally described by Wilson in 1811. Currently nine
subspecies of seaside sparrows are recognized (American Ornithologists'
Union [A.O.U.] 1957, 1973), including the nearly extinct dusky seaside
sparrow (A. m. nigrescens). Beecher (1955) postulated that formation of
the races of seaside sparrows was due primarily to geographic isolation
caused by post-glacial rise in sea level and the concurrent drowning of
river mouths forming bays (also see Funderburg & Quay 1983). All but the
southernmost populations of the nominate race are migratory. The other
races are generally considered to be non-migratory.
Scott's seaside sparrow (A. m. peninsula) was named in honor of W.
E. D. Scott and described in 1888 by J. A. Allen. The type specimen was
collected near Tarpon Springs (Pinellas County, Florida). A. m.
peninsula ranges from Old Tampa Bay (Hillsborough County, Florida)
north to Pepperfish Key (Dixie County, Florida) (A.O.U. 1957).
Austin (1983) and I (McDonald 1983a) have briefly discussed and
annotated the taxonomic history of the seaside sparrow assemblage. The
distinguishing plumage color characteristics of the seaside sparrow
subspecies are thoroughly described and compared by Funderburg and Quay
(1983). Three museums in the United States house good representative
collections of seaside sparrows that I have examined: The American
Museum of Natural History, the United States National Museum of Natural
History, and the Florida State Museum.
Seaside sparrows are generally recognized by their dark gray-brown
head and body (total length about 14 cm), narrow black streaks on the
breast and flanks, yellow lores and wrist spots, and long bills. The
tail is relatively short and narrow and the feet and legs are relatively
large, in proportion to the size of the bird. When flushed, seasides
characteristically fly short distances and then drop back into the marsh
vegetation. Unlike other sparrows, seaside sparrows eat many
crustaceans and insects, but few seeds.
In his original description, Wilson succinctly described seaside
sparrow habits when he said: "Amidst the recesses of these wet sea
marshes, [the bird seeKs the rankest growth of grass and sea weed, and
climbs along the stalks of the rushes with as much dexterity as it runs
along the ground, which is rather a singular circumstance, most of our
climbers being rather awkward at running" (Wilson 1811, p. 68).
Scott's seaside sparrows are among the darkest of the seaside
sparrows. As in other races a certain degree of individual color
variation exists. Some birds approach the lighter colored A. m.
maritimus in shading on the dorsum; others approach the darker A. m.
nigrescens. Early taxonomists made no mention of this color variation,
although Griscom (1944) recognized it. Austin states: "A gradual cline
is evident from the smaller, grayer populations in the south
peninsulaa) to the slightly larger, darker, and dorsally browner birds
in the northwest corner of the range in the Wakulla area (juncicola)"
(Austin 1968a, p. 838). However, W. Post and H. W. Kale (pers. comm.),
most familiar with the morphological variations in the southern
subspecies, agree that there are apparently no characteristics
consistently separating A. m. peninsula and A. m. juncicola (Wakulla
seaside sparrow). The range of juncicola is contiguous with peninsula
near Pepperfish Key, Florida and extends to southern Taylor County,
Florida. Thus, juncicola should probably be merged with peninsula,
which has taxonomic priority.
In all seaside sparrows the sexes are identically colored, but males
are slightly larger. In my study at Cedar Key I routinely took wing
length (wing chord) and weight measurements. For adult males and
females the mean wing chord measurements and 95%7 confidence intervals
were 58.9 (+0.4) mm and 54.0 (+ 0.3) mm; and mean weights 22.5 (+ 0.6) g
and 19.6 (+ 0.7) g, respectively (N=134 males and 78 females). Thus
females were 937o as large as males based on wing chord measurements and
89% as large based on weight measurements. Because the 99'% confidence
intervals for wing chord did not overlap, male and female adults handled
outside of the breeding season could be sexed using wing chord. During
the breeding season the age and sex of birds could more easily be
determined using other criteria. Females possessed a vascular, edematous
brood patch about 1.8 cm wide and males had a cloacal protruberance of
about 2 mm. Fledglings and older hatching-year birds had a
characteristic paler plumage pattern.
Project History and General Methods
The study site near the Gulf coast town of Cedar Key, Florida, was
established by William Post in December 1978. Post investigated the
habitat and reproductive biology of the birds for two years, under
contract with the Endangered Species Program of the Florida Game and
Fresh Water Fish Commission. Information and results obtained from his
project were to become part of a management plan for the rare and
endangered Atlantic coast population of A. m. nigrescens. Post gridded
the marsh with stakes, began color banding of birds, mapped vegetation,
sampled the invertebrate fauna, studied the interspecific influence of
fish crows (Corvus ossifragus) and rice rats (Oryzomys palustris) on
sparrow reproduction, and recorded other descriptive data pertaining to
the morphology and life history (Post 1980, 1981a, 1961b; Post &
Greenlaw 1982; Post et al. 1983; Greenlaw & Post 1965).
Post concluded his field work in the summer of 1980. I accompanied
him to the study site several times early in 1981, and then assumed
responsibility for the study site and birds later in the spring of 1981.
During the breeding seasons (March-June) of 1981-1982 I familiarized
myself with the marsh and the birds' behavior, and continued color
banding adults and some nestlings. I spent an average of 50 days in the
field each of these two years, observing and tape recording
In 1983 and 1984 I continued comprehensive observations and color
banding of my Florida study population, each year averaging about 70
days in the field from March through June. Behavioral observations on a
field day consisted of 2-4 hours of watching, recording some of the
vocalizations, and describing behavior and territories. I recorded
spoken notes on a tape recorder, and included the location of birds and
activity time (measured with a stopwatch). I later transcribed tapes
and analyzed the data.
The major investigation of my study--temporary song muting--was
conducted during the breeding seasons of 1983-1984 and is described in
Chapter IV. In the spring of 1965 I spent 15 days in the field censusing
returning and new males and conducting playback experiments with female
seaside sparrow vocalizations.
Throughout this report the data designated as having been collected
in 1979-1980 are from Post's unpublished and published work and are used
with his permission. All other data were collected and analyzed by me.
I used non-parametric statistical tests (Siegel 1956; Conover 1980) for
The 30-ha salt marsh study site was north of the Waccasassa Bay of
the Gulf of Mexico. The site was 6 km NNE of the town of Cedar Key, Levy
County, Florida, and within the Sumner quadrangle, USGS Map (29 11' N,
830 00' W). The physical boundaries of the marsh, exterior to the core
gridded study area, were Prodie Creek on the SW, Live Oak Key and
Waccasassa Bay on the S, and Dorset Creek on the NE. The property was
The boundary between the marsh and Waccasassa Bay was not sharply
defined. The shoreline was dotted with oyster bars and many small
islands and was cut by numerous tidal creeks. Except for these creeks,
which ranged from 0.5 to 1.5 m deep at mean high tide, the marsh was
flat. Tides averaged 0.8 m. Most years one or two flooding episodes
occurred during the breeding season, destroying any existing nests of
seaside sparrows. These floods were most often generated by prevailing
winds from the south, driving water in from Waccasassa Bay, combined
with a natural (high) spring tide event. The water level during these
floods usually rose about a meter above mean high tide. Average salinity
measured by Post (1980) at 32 stations on 24 April 1980 was 19.03 + 1.09
Data on cloud cover, air temperature, and wind direction and
velocity were collected at about hourly intervals throughout each field
day. Phenological records such as flowering dates and spring migration
observations were also kept. More complete daily weather information
(maximum and minimum temperatures and rainfall) for all years was
recorded by a National Oceanographic and Atmospheric Administration
(NOAA) station near the town pier of Cedar Key.
My behavioral observations and the handling of birds were carried
out under mild weather conditions (18-33 C, wind <20 km/h) during the
months of February through June. During my 5-year study, however, I did
visit the marsh in all months of the year and under virtually every
weather condition. Temperatures I recorded ranged from 3 C (January) to
l40 C (August). On typical sunny days during the height of the breeding
season (April and May) the mid-morning temperatures averaged 26 C. For
those field days on which I took detailed behavioral observations, the
wind velocity usually ranged from about 2 km/h (just prior to sunrise)
to about 12 km/h by 0900, and then 16-24 km/h by early afternoon.
Prevailing winds were mostly from the southwest. A few sultry field
days were virtually windless. Winds approaching gale force (50+ km/h)
occurred occasionally in the spring and fall.
In September 1985, Hurricane Elena touched the Cedar Key area. My
surveys the following week and in 1986 indicated no discernible
population decline in the three bird species breeding on this marsh
(seaside sparrows, marsh wrens [Cistothorus palustris], and clapper
rails [Rallus longirostris]).
The six-year average population densities of the three resident
bird species were seaside sparrows-2.5 + 0.1 birds/ha, N=253; marsh
wrens--0.6 +0.3 birds/ha, N=23; and clapper rails-0.5 + 0.1 birds/ha,
N=59 (Post 1981a; McDonald 1982, 1983b, 1984, and my unpublished surveys
for 1984 and 1985). In addition to these residents, migratory
sharp-tailed sparrows (Ammodramus c. caudacutus) wintered on the marsh.
They regularly arrived in the last week of September and left 'in the
second week of May. The population density of sharptails averaged about
2/ha. Other bird species seen foraging or resting on the study site
were those commonly found in Florida Gulf Coast salt marshes (Post
1981a; McDonald 1982, 1983b, 1984).
As described below in the section on reproduction, most seaside
sparrow nest losses were attributed to predation, primarily by fish
crows and rice rats. The rice rats dwelt on the marsh. Their density was
about 8/ha (Post 1981b). I also found evidence of predation by
transient racoons (Procyon lotor).
Other species of mammals were occasionally observed: river otters
(Lutra canadensis) played on the bank edges; Atlantic bottlenose
dolphins (Tursiops truncatus) and very rarely, manatees (Trichechus
manatus) swam in the larger tidal creeks. The only reptile I saw on the
study site was the Gulf Salt Marsh Snake (Nerodia fasciata clarki),
observed on three occasions.
Invertebrate fauna and seaside sparrow foraging.
The most obvious and abundant invertebrates on the marsh were
fiddler crabs (Uca rapex) and Gulf periwinkles (Littorina irrorata).
Genoni (1984) reported additional mud-inhabiting invertebrates from this
marsh. Terrestrial invertebrates were also censused previously by
sweep-netting the vegetation during the sparrows' breeding seasons (Post
et al. 1983). By percent of total sample, these were Tettigoniidae
(54.3%), Lycosidae (18.8%), other spiders (7.8%), and Lepidoptera
(Noctuidae and Pyralidae) (3.0%). Six additional invertebrate families
each represented less than 5% of the total sample. Post et al. (1983)
found that 85Y% (by volume) of the nestling's diet consisted of these 10
groups of arthropods.
The invertebrate food species consumed by adults on this marsh are
probably nearly the same as those eaten by Scott's and other subspecies
of seaside sparrows on similar marshes. Howell (1928, 1932), Oberholser
(1938) and Wilson (1811) examined stomach contents of adult Scott's,
Smyrna (A.m. pelanota), Louisiana (A. m. fisheri, and dusky (A. m.
nigrescens) seaside sparrows. In addition to the arthropod groups listed
above, which are known to be fed to nestlings at Cedar Key (and
presumably eaten by adults), these authors found adults had eaten marine
"worms," small crabs and other crustaceans, beetles, dragonflies, flies,
wasps, bivalves, gastropods, and some "weed" and grass seeds. (Audubon
[18311 said that a pie he made of seaside sparrows could not be eaten
due to its "fishy savour," surely attributable to the birds' having
consumed mostly salt marsh invertebrates!)
With the assistance of a biologist familiar with marsh
invertebrates, I examined the stomach contents of eight adult birds from
my study site. Surprisingly, three of the stomachs were virtually empty.
These males had died early in the morning during the breeding season,
perhaps prior to foraging. The other stomachs contained mostly
arthropod exoskeletons (fragments of crabs, insect adults and pupae, and
one small spider), snails (Pyramidellidae and Marginellidae), and
vegetation. Post et al. (1983) presented convincing evidence that food
was plentiful and accessible to the Cedar Key birds throughout the year.
I rarely observed birds drinking. Several times I saw then imbibe
dew from the vegetation, and once I saw a bird drinking and bathing at
the edge of a shallow tidal creek. Although no passerines have salt
glands, seaside sparrows do have the ability to concentrate urine when
consuming salt water (Poulson 1969).
Vascular plant species on the study site were described in detail by
Post (1980). In order of relative cover, the major plants were smooth
cordgrass (medium height) (Spartina alterniflora) 38%, black rush
(Juncus roemerianus) 26%o, seashore saltgrass (Distichlis spicata) 23%,
and perennial glasswort (Salicornia virginica) 8%7. There were no woody
plants within the gridded portion of this marsh. Also, there were no
pannes (bare mud areas devoid of vegetation) until September 1985, after
the passage of Hurricane Elena near the Cedar Key region. Apparently
some stands of Spartina were submerged for at least several days during
the storm; consequently these drowning-susceptible plants died.
Size and Demarcation of Study Sites
Post established two contiguous study areas, Cedar Key West ("CKW,"
10-ha in area) and Cedar Key East ("CKE," originally 20-ha in area ).
Although CKW and CKE were contiguous, the study populations of seaside
sparrows living on each site were separated by 200-400 m, and the
populations did not interact. Both study areas were gridded with 2-3 m
high wooden stakes placed at 25 m intervals. Stiff metal prongs on the
tops of the markers discouraged their use by predatory birds. Stakes
were alpha-numerically designated and could be read from at least 50 m.
Additional markers were placed around the peripheries of the study areas
for reference. I concentrated my preliminary observations on the CKW
birds in 1981, then switched to CKE study area (which I enlarged to
30-ha in 1954) for the remainder of my project.
Reproduction and Reproductive Behavior
Overview of Annual Cycle
Fig. II-1 graphically summarizes the reproductive cycle of Scott's
seaside sparrows at the Cedar Key study site. The cycle commenced in
early March with the onset of regular singing by males and subsequent
territorial establishment and mate acquisition. The peak of the breeding
season (as indicated by the number of newly completed clutches) for the
six years 1979-1984 occurred during the second and third weeks in May.
In a typical spring the first clutches were completed around the
beginning of April, and the last clutches by the end of June.
Most clutches (855) were completed by the end of May. Virtually all
breeding and territorial defense activities ceased by mid-June. Both
adults and juveniles entered a prolonged molting period during the early
fall and remained difficult to observe until the following early spring.
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Annual Cycle of Reproductive Behavior
Territorial establishment and mating
Breeding behavior of Scott's seaside sparrows near Cedar Key began
in late winter (February) with sporadic singing of adult males on warm,
windless mornings. Young adult males, hatched the previous spring, also
began to sing imperfect subsongs. By early March all males were singing
typical primary songs, and females began to associate with males.
Females solicited male affiliation with the "whinny" and "tchi" calls
During these early weeks of the season, weather influenced the
intensity of singing and other observable breeding activities. Wind
velocities greater than 25 km/h accompanied by temperatures less than
200 C caused a nearly complete cessation of overt territorial and mating
behaviors. Mild weather, even in early February, greatly enhanced
regular singing activity and behavioral interactions. In addition to
this immediate influence of atypical weather, prolonged cool
temperatures delayed the onset of breeding within a given season, and
hot weather in late May caused an early cessation of breeding
activities. The early spring of 1963, for example, was unusually cold:
average daily temperatures for March were about 50 C below normal
throughout mid-Florida. The breeding activities of the study population
at Cedar Key were about 2 weeks delayed that year-I did not find a
completed clutch until 26 April. On the other hand, the unusually warm
February of 1985 certainly must have accounted for my finding fledged
seaside sparrows on 16 March and fledged marsh wrens on 23 February,
both record early nesting dates for these species for any known breeding
Most males re-established the same territories from year to year and
vigorously defended these during March and early April, the period when
the most fervent territorial disputes between first-year and older
adults and between residents and floaters broke out. By May territorial
ownership and boundary disputes were rare, seemingly occurring only when
floaters attempted (always unsuccessfully) to take up residence on an
occupied territory. The intensity of singing (as measured in minutes of
singing/hour) also declined gradually after a peak in early April. By
June there was only sporadic singing activity occurring daily from just
before sunrise to about one-half hour after sunrise.
Most birds paired by mid-March. The mates remained paired over the
remainder of the breeding season. I never observed a natural incidence
of divorce, although Werner (1975) reported several instances of
re-pairing in his Cape Sable birds in the same breeding season. Seven
percent of 97 non-experimental territorial males remained bachelors
throughout the breeding season in my study. Werner (1975) reported that
about 12% of his 111 Cape Sable seaside sparrows were bachelors.
Apparently the adult sex ratio of the breeding birds was slightly skewed
in favor of males. Although Post (1980) assumed that most unmated
territorial males were probably first year birds, my longer study of
these marked birds indicated no significant difference in the
proportions of unmated older territorial birds and unmated first-year
territorial birds (X2=0.4, N=10 bachelors, df=l, P>0.5).
My observations over the years also suggested that returning males
tended to re-mate with their female of the previous year, if she also
returned the second year. I documented mate retention using data for
non-experimental males and females present in both 1963 and 1984, the
years for which I had the most complete data. Of the 10 cases in which
both members of the pairs were present in succeeding years, there were
five re-mates. Mate retention from year-to-year also occurs in northern
seaside sparrows on Long Island, New York (Jon Greenlaw, pers. comm.).
Werner (1975) also stated qualitatively that there was some degree of
year to year mate retention in his Cape Sable seaside sparrow subjects.
Females solicited copulations with a slow, low-pitched variation of
the "whinny" vocalization accompanied by quivering bilateral wing
raises. This display was given at ground level with the bird concealed
in the marsh vegetation. A nearby male (usually the mate) was
immediately attracted to this enticing behavior and would quickly
copulate by mounting the female briefly with fluttering wings and then
bounce off, landing several meters away. The male sometimes gave one or
two songs immediately after copulation, whereas the female was almost
always silent afterwards.
Typical bouts of copulation involved three to five mounts during
time intervals of 0.5 to 1.5 hours. All of the copulation bouts I
observed occurred in the mornings. During this period the female
sporadically gave her solicitation whinny, while the male remained
within a 15 m radius of her and sometimes sang. Of the 96 copulation
bouts I observed under non-experimental conditions, all but three were
between birds I had previously known or subsequently knew to be mates.
On the remaining three occasions I observed neighbor or floater males
sneak in and copulate with a soliciting female while the mate was
vigorously singing or confronting other birds on the opposite side of
Nests, eggs, and early development
Although this was primarily a behavioral study, nesting and other
reproductive data were routinely collected during the breeding seasons
of 1981-1904, and in some cases were consolidated with Post's
Seaside sparrow nests are notoriously difficult to find in salt
marshes. My early efforts to find nests by dragging a chain through the
vegetation, by trying to flush nesting females by walking transects, and
even by using a bird dog were largely unsuccessful. I eventually
learned to locate most of the nests of subject birds by close
observation of the parents.
For all nests I found, I noted date and time of discovery, parents,
location relative to the grid system and territorial boundaries, and
vegetative microhabitat. Because I wished to minimize human
interference, I handled only a sample of the nests and nestlings that I
was aware of. The additional information taken for these sample nests
was form of nest cup (open or domed), height from ground to bottom of
cup, dimensions of cup (inside and outside diameter, inside and outside
depth), material used in constructing nest, number of eggs or
hatchlings, egg dimensions, hatchling weight (for 11 individuals), age
of hatchlings, and daily survival. I also weighed seven nests collected
The following summarizes my descriptive data on 194 nests. Two
nests had well-defined domes and entrances. I detected no preferred
directional entry pattern of attending parents for any of the nests,
although the nests of some subspecies of seaside sparrows are mostly
domed and have distinct entrances. About half of the nests were built
in Distichlis and the remaining roughly split between Salicornia and
Juncus microhabitats. All nests were constructed primarily with the
Distichlis grass; a few had small Spartina leaves woven in. The average
height of the nest (as measured from the ground to the bottom of the
nest cup) was 35 cm. Average nest size measurements were: outside
diameter of cup 9.3 cm; inside diameter of cup 5.4 cm; outside depth of
cup 5.3 cm; inside depth of cup 3.3 cm. Also in contrast to other
subspecies, at Cedar Key the average clutch size was smaller (3.02 +
0.17 eggs, N=194 nests), compared to about 3.65 in New York (Post et al.
Average egg dimensions were 20.6 mm X 15.7 mm (N=35), and egg
weights averaged about 2 g. While exhibiting minute individual
variation, the color pattern of the eggs was essentially the same as
described for seaside sparrows in detail elsewhere (Austin 1966a).
Egg and nest cup dimensions for Scott's seaside sparrows at Cedar
Key were within the ranges reported for other subspecies in the
literature (Austin 1968b; Norris 1968; Sprunt 1966; Trost 1966;
Woolfenden 1968; Werner 1975; Greenlaw pers. comm.) and in collections I
measured at the American Museum of Natural History, the United States
Museum of Natural History, and the Florida State Museum.
I categorized nest placement within a pair's territory as "edge" or
"center." An edge nest was so designated if it was built in the outer
fourth of the total area of the territory. I found no significant
difference in the birds' tendencies to locate nests at the territory
edge versus towards the center (X 2=0.7, N=194, df=l, P>0.4).
Only 116 nestlings were directly observed, but others were known to
be in active nests. The young remained in the nest 9-11 days. Their
weights increased from 2.2 g on Day 0 to 15.1 g on Day 10. The few
other morphological data I took on these birds agree with Werner's
(1975) extensive quantitative morphological data and photographs of
nestlings taken days 1-8 for Cape Sable seaside sparrows.
Norris (in Austin 1968a) gave a detailed description of nestling
Louisiana seaside sparrows (A. m. fisher) and the behavior of the young
and their parents. My observations of Scott's seaside sparrows at Cedar
Key are very similar to Norris's in Louisiana.
Nest building (by the female only) began on the day of or the day
after copulation bouts. Females did not re-use nests, but built a new
nest for each new clutch. The female usually completed building her
nest within a day and laid her clutch of three eggs (rarely four) over
the next five days. The eggs were laid one a day, at any time during the
day. Infrequently females that were building nests, laying, or
incubating, would copulate with their mates. Incubation was by the
female only, for 11-12 days.
Most years the first young of the season hatched around the second
week in April (Fig. II-1). All of the young hatched within 24 hours and
began to gape and utter soft "peeps" on the day of hatching. The eyes
were fully opened by day five and at about this time the begging
vocalizations changed from a "peep" to a "churp" and became more
intense. Some nestlings fledged and were able to run about as early as
Day 9. Most began short flights about Day 13.
The hatchlings remained in the nest for 9-10 days and were fed by
both parents. The combined average feeding rate was 3.2 visits per
hour. Parents also maintained a clean nest by removing fecal sacs. Post
et al. (1983) determined the diet of hatchlings older than 3 days by
placing pipe-cleaner ligatures around their necks and then removing the
food from the young or the nest cups after an hour had elapsed. The
most important food groups for the nestlings were found to be the
insects of the taxa Tettigoniidae and Lepidoptera and spiders of several
families. These invertebrates constituted 85% of the nestlings's diet.
Both parents continued to feed the young for 15-20 days after
fledging. If the breeding season had not progressed too far (i.e. prior
to about 15 May), a female with fledged young would begin to renest
about a week after the first brood had fledged and would leave the care
of fledglings to her mate. I noted five such cases in 84 pairs.
Since most nests were destroyed before young fledged, seldom did a
pair actually have the opportunity to rear a second brood within a
season. From late March through early June, unsuccessful parents would
try repeatedly to raise a family. The average number of nesting attempts
per season of 84 pairs (1981-1984) was 3.7, and the interval between
nest destruction and renesting was 5.7 days. In 1984 I observed one
pair attempt seven nests, all unsuccessful.
Fathers began to avoid their first brood after tending their
fledglings for about three weeks, or after their second successful
clutch hatched. They chased their fledglings (as well as any other
juveniles) off the parental territory and started to devote their
attention to their new brood. After nesting had stopped family groups of
fledged, dependent young and their parents were often observed during
the months of June and July. Adults without families were seldom seen
during this period, especially during the hot daytime hours.
By August most juveniles were independent and began to form loose
groups of about three to eight. Sometimes adult males associated with
these groups, which persisted through October. Juvenile males gave
occasional bouts of imperfect subsong in August and September, and
rarely through the winter. Although present (as evidenced by occasional
mist net captures), adult females were rarely seen in summer.
From late September through October there was a resurgence of easily
observable but essentially non-vocal behavior, such as foraging and
territorial defense. From these observations and my intensive mist
netting in the fall of 1982 and 1983, I concluded that adult males and
females remained within a radius of about 250 m of their previous spring
territory throughout the year. Juveniles appeared to wander a great
deal more, perhaps as far as several km.
Little is known regarding the fate of the fledgling seaside sparrows
at Cedar Key or elsewhere. Of the total of 98 hatchlings and fledglings
Post and I banded at Cedar Key, I recaptured only 4 during my intensive
netting 1982-1984. Presumably the emigration and general mobility of
fledglings as well as of non-territorial older birds are mechanisms for
the birds' locating and colonizing any unoccupied territories and viable
The Cedar Key population appeared stable (average density 2.5
birds/ha) throughout the 7 years 1979-1985. Adult birds with territories
were relatively long-lived. By the end of 1984, I had studied subject
males from 1 to 4 years. According to banding records, two males were at
least 5 years old, and one was at least 6 years old.
The adult post-nuptial molt (and only annual molt) of their nuptial
plumage began in early July, and the post-juvenile molt began in late
July. Both molts were completed by October.
The seasonal weight variation was slight but significant. Both
sexes were heavier in winter than in summer, but the difference was not
as great as in the nominate migratory seaside sparrows (Post 1980).
Productivity, Survival, and Reproductive Success
I summarized parameters of reproduction for seaside sparrows at
Cedar Key in Table II-1. The data combine my unpublished observations
(1981-1984) with Post's observations (1979-1980), as given in Post
1980 and Post et al. 1963.
Post (1981b) intensively studied seaside sparrow reproduction and
factors that affected productivity during his 1979-1980 project. He
also compared these characteristics of reproduction in A. m. peninsula
to another well-studied population, A. m. maritimus in New York (Post &
Greenlaw 1982; Post et al. 1983). I combined the two years of Post's
data with reproductive data I collected 1981-1984.
Studies of nest productivity should consider whether nest failures
are due to human disturbance. I did not test if my visitations affected
the nesting success I observed. Post (1980), however, did test for an
observer effect using the methods of Mayfield (1975) and Johnson (1979)
and found that the frequency of nest visitation did not affect nesting
success of Scott's seaside sparrows.
Table II-1. Summary profile of territoriality and reproduction
Scott's seaside sparrows at Cedar Key, Florida, 1979-1984
Territories, Mating, and Return Ratesa
Mean territory size
Ecological density of territorial males
Mean annual return of territorial males
Proportion of re-mates
Proportion of bachelor territorial males
Ratio unmated first year/older males0
Mean length of study of male in population
Productivity and Survivala,c
Mean clutch size (C)
Mean no. clutches initiated/female/yr (I)
Probability of egg producing fledgling (S)
Mean length of breeding season
Proportion of nests producing fledglings
hest success ratio of young/older breeders
Adult annual survival male return) rate
Juvenile survival rate
Production of fledglings->breeders next yrb
1759 + 242 m2
3.02 + 0.17
Combined data from Post 1980; Post et al. 19b3; and author's
unpublished observations. Probability level: h.S.=P>0.05.
bSee text for explanation of calculations.
cBased on 194 nests
At Cedar Key the probability that a nest would produce fledglings
was remarkably low, but because females renested within 7-8 days of nest
destruction, the population seemed to have remained stable from 1979
through 1985. That is, bird density remained about the same over the
years we censused the study population (Post 1980, 1981a; McDonald 1982,
1983b, 1984, and my unpublished data).
Post et al. (1983) calculated probability of an egg's surviving 21
days (through the egg and nestling period) and producing a fledgling to
be only 0.06 (Post et al. 1983). This contrasts with an egg survival
rate of about 0.35 in New York.
Of a total (McDonald and Post) sample of 194 nests whose fates were
carefully documented, only 12 (6>7) produced at least one fledgling. The
major causes of nest mortality at Cedar Key were flooding, and predation
by fish crows and rice rats. Eight (4%) of the nests failed due to
desertion. Neither Post nor I ever suspected hatchling death due to
starvation. I found only a few instances of partial nest mortality.
Eleven (2%) of the 473 eggs I observed in the field failed to hatch and
were presumably infertile.
Destruction by flooding accounted for the mortality of 17 (9%) of
the nests. Normal tidal fluctuations in water levels seldom reached the
bottom of the nest cup (about 35 cm above the ground). However, in most
years at least one major unpredictable flooding of the marsh occurred.
For the seven years (1979-1985) there were nine such floods during the
Predation by fish crows destroyed 37 (19") of the total nests. Fish
crow predation was assumed when eggs disappeared without leaving shell
fragments or a disturbed nest (indications of mammalian predation). Fish
crows were about three times more likely to prey upon nests with
hatchlings than on those with eggs.
Post (1981b) concluded that nesting in Juncus should be preferred by
the birds because Juncus stands were less likely to be flooded and
because this vegetation provided cover protection from fish crow
predation. However, rice rats on the marsh apparently discouraged
seaside sparrows from nesting more in Juncus by destroying their nests
(Post 1981b). The birds were found to nest more frequently (857 of the
total nests) in less dense Distichlis and Salicornia, even though nest
failure was more likely to occur in these vegetation types, as compared
to failures in Juncus (Post 1981b).
The remaining 120 (624) of the total nests were destroyed by rice
rats and unknown predators (probably racoons).
Post (1961b) tested whether rice rats were actually destroying nests
by placing tin cylinders around nests. These were open at the top,
allowing entry by parents and aerial predators but excluding small
mammals. Forty-eight percent of 42 experimental nests with this
protection produced fledglings, whereas only 6%a of the 34 control
(unprotected) nests had young that fledged.
To summarize: about 80% of the nests at Cedar Key were destroyed by
predation. This contrasts with findings in New York where fewer seaside
sparrow nests were destroyed by predators and more losses (about 65% of
the total nest mortality) were due to flooding or rains, desertion,
hatching failure, and unknown causes (Post et al. 1983).
I report productivity as the number of fledglings/female/year.
Post's data (1980) were combined with mine: Post observed 109 clutches,
and I observed 85 clutches. Productivity was determined by the method
of Ricklefs and Bloom (1977): Productivity = Mean Clutch Size (3.02) X
Probability of Egg Success (0.06) X Number of Clutches Initiated by a
Female/Year (3.7). (The term "productivity" and its values are roughly
equivalent to the "realized specific natality rate" parameter that is
conventionally calculated using life table data.) The six year average
productivity for 1979-1984 was 0.67 fledglings/female/year. This value
contrasts with the much higher rate of 4.25 for the New York population.
New York females produced about six times as many young within their
average 75 day breeding season as the Florida birds did in their average
95 day season. The annual survival, however, was lower in New York
(Post et al. 1983).
I determined the adult annual survival rate at Cedar Key to be about
0.78, based on the return of 51 of 65 adult males over the years
1980-1983 and assuming a roughly equal sex ratio. This figure represents
a minimum value, since some birds may have emigrated. This is a
relatively high value for a small Passerine bird. Werner (1975)
estimated a 0.88 survival rate for the likewise non-migratory A. m.
mirabilis, based on a one year return sample. Adult survival is lower
for migratory A. m. maritimus--only about 0.45 (Post 1974).
I estimated the juvenile survival rate to be about 0.67. This figure
was determined using the method of Post et al. (1983) and using their
estimated ratio of juvenile/adult survival (0.85, as determined from
returns of banded nestlings and adults). Thus, I multiplied the adult
annual survival rate of 0.78 by the ratio of juvenile/adult survival of
0.85, giving 0.67.
Although I did not have enough data to directly calculate net
reproductive rate (R0) using life table parameters, I suggest that the
Cedar Key population of seaside sparrows is maintaining its numbers for
the following reasons: First, there was no decline in population
density over the years. Additionally, my experiments in 1983-1964
demonstrated that floaters (itinerant males without territories or
mates) were always available to take up residence on territories they
perceived as unoccupied. Secondly, the reproductive data I do have
suggest that enough juveniles were produced and survived to replace
non-returning adults. That is, using my calculated productivity figure
of 0.67 fledglings/female/year and Post's (1980) juvenile survival rate
of 0.67, each breeding female (pair) produced 0.45 first-year birds.
Assuming a sex ratio of about unity, each female produced 0.225
first-year female breeders. If the minimum adult annual survival rate
was 0.78 and applicable to both sexes, then the annual adult female
mortality rate was 0.22 (1.00 0.78 = 0.22) or less. Since 0.225 is
about the same as 0.22, these reproductive data do substantiate my
observation that the population size has been constant over the years.
Post et al. (1963) calculated a net reproductive rate of 2.72 for the
increasing New York population. The authors also state that the net
reproductive rate for the Cedar Key population was 1.11 (based on
1979-1980 data), but it is unclear how this figure was determined
without life table (i.e. survivorship) data.
These New York and Florida projects are the only major long-term
studies that report and summarize detailed reproductive data. Other
papers that contain some data on breeding success and productivity for
other subspecies of seaside sparrows are Nicholson (1946), Woolfenden
(1956), Stimson (1956), Norris (1968), Sprunt (1968), Stimson (1968),
Trost (1968), Woolfenden (1968), Worth (1972), and Werner (1975).
Territories and Territorial Behavior
Definition and Methods of Determining Territories
The working definition of "territory" I used in this study was "any
defended area" (Noble 1939, p. 267). My use of the term "defended"
implies that a bird exhibited aggressive behavior towards another, with
the seeming intention of driving or keeping the other out of his or her
territory. I considered vocalizations and visual displays directed at
another bird to be defensive behaviors. This study dealt primarily with
aspects of male territoriality, although female seaside sparrows also
exhibited territorial behavior. I considered a territory to be an area
in which a male invariably challenged intruders with singing, displays,
or other overt aggressive behaviors.
All of my behavioral observations were made relative to the grid
markers. I drew territory maps for the entire study population weekly,
by connecting the points of the most peripheral singing perches with
lines. I traced the territories thus delineated with a compensating
polar planimeter and then calculated the enclosed areas. When a map
indicated a boundary had moved by 15 m or more, I considered that to be
a territorial boundary shift. The summary information regarding
territory sizes and location reported in this chapter were those
measured for non-experimental birds during the first week of May unless
Description of Territories at Cedar Key
Territories at Cedar Key were all purpose--used for mating, nesting,
and feeding. Mated pairs exclusively occupied territories throughout
the breeding season, although boundaries between territories fluctuated.
Only two instances of complete territory relocations were noted for 65
non-experimental males studied 1979-1982.
The mean yearly return rate for male territorial birds was 797%
(N=89). There was a strongly significant tendency for males to
re-establish territories on the same sites in succeeding years. (My
conservative null hypothesis was: Returning males are as likely to
establish a new territory as they are to re-establish their old
territory. My sample sizes and statistics were: 43 re-established
territories of 52 observed returnees; X2 one-sample test, X2=21, df=l,
P<0.001). Year-to-year retention of territories has also been reported
qualitatively in the few other studies of marked populations of seaside
sparrows (Worth 1972; Werner 1975; Greenlaw pers. comm.).
The territory sizes of non-experimental birds at Cedar Key ranged
from about 200 to 4000 m2. The mean size was 1759 m2 (SE=242 m2, N=65).
This average territory size for the population did not change
significantly over the years 1982-1984 (Kruskal-Wallis one-way ANOVA,
N=43 territories of non-experimental males, df=2, H=0.83, P>0.5). In
comparing the individual males' territories from year to year, I found
no significant increase or decrease in their territorial areas (Wilcoxon
matched-pairs signed-ranks test, N=23, T=91, P>0.05).
The boundaries of territories did not follow any apparent natural
landscape divisions, such as vegetation type borders or small tidal
creeks. However, larger tidal creeks (>20 m wide) did often separate
Several studies of northern seaside sparrows (Post 1974; Post &
Greenlaw 1975) contain a few quantitative data describing territorial
behavior. Other authors (e.g., Audubon 1831; Nicholson 1946; Norris
1968) anecdotally portrayed territorial and breeding behavior of seaside
sparrows, some in detail and many from an anthropomorphic perspective.
Those reports that best characterize territorial birds and their social
interactions are Norris (1968), Worth (1972), and Werner (1975).
At Cedar Key males began to establish their territorial boundaries
in early March by singing regularly from song perches, usually clumps of
elevated vegetation such as Juncus tussocks located at the edges of
their territories. Overt aggressive encounters were also first observed
at this time and became most numerous in April. Behaviors of such
encounters, in order of frequency of occurrence, were chasing bouts
accompanied by strident "tchi," "zuck," and rapid "tuck" calls;
supplanting (a challenger flew towards a perched bird, and the perched
bird left without dispute); and short-range "facing off" displays,
wherein the participants engaged in wing raises, bobbing, bill
thrusting, and wing and tail flick displays, co-occurring with the
"tuck" and "tchi" calls and "whisper songs."
These Early Season territory-establishment behaviors, as well as
male-female pairing chases, decreased significantly in frequency and in
duration as the breeding season progressed into May. By the end of the
breeding season (June), territorial males seldom disputed intrusions by
neighbors and floaters.
Prior to experiments I conducted in 1983-1986, Post and I believed
that there were no excess males trying to establish territories and
consequentially compress existing territory sizes. I found, however,
that there were such-males, as discussed below in Chapter IV.
Females definitely displayed aggressive behavior towards both
intruding males and other females throughout the season, although I have
few quantitative data on the extent of their involvement in
territoriality. In contrast to males, which were more likely to give
short distance aggressive displays and calls, females were more likely
to supplant and chase intruders. Of the total 3,159 instances of overt
aggressive behavior I analyzed between seaside sparrows in March and
April, 22 percent involved females. Only 5 percent were known to be
female-female encounters. Observations of such encounters were
difficult to make, because females spent more time than males in dense
vegetation. The frequency of female chases of intruders from the
pairs's territory averaged 2.7 chases per hour in late March and early
April. These chases were usually accompanied by the "tchi"
vocalizations and sometimes by a fast rendition of the "whinny"
vocalization (female solicitation call).
Reactions to Other Species of Birds and to Humans
I observed no vocal or other behavioral interactions of seaside
sparrows with resident clapper rails or marsh wrens. Each of these
species seemed oblivious to the sounds emitted by the others. Calls and
songs often overlapped, even when given within close range (<15 m). This
is in contrast to other studies of bird communities, in which singing
characteristics of several species are influenced by each other (e.g.
Popp et al. 1985). Several times I did note that seasides alternated
songs in a definite pattern (countersang) with migrating red-winged
blackbirds (Ageliaus phoeniceus) and bobolinks (Dolichonyx oryzivorus).
Cruising fish crows (notable nest predators of seaside sparrows) almost
always caused seasides to stop singing and sometimes to give "si
twitter" alarm calls (23 observations of low-flying fish crows during
song, 18 instances of song ceasing).
Wintering sharptail sparrows incited aggressive behavior from
seasides, especially when the sharptails began to sing in early May. The
seaside's aggressive behavior was identical to that directed towards
conspecific intruders. Early in the breeding season the mostly silent
sharptails were tolerated and unchallenged. On 17 occasions I heard
distinct countersinging between seasides and sharptails, although their
songs are quite different.
My study population of seaside sparrows seemed oblivious to my
presence, except when I approached to within 5 m or handled them. The
birds were more wary when I was accompanied by field assistants. Other
researchers have made similar observations regarding the "tameness" of
their subject populations of seaside sparrows (Sprunt 1968; Post 1974).
At Cedar Key curious sparrows and wrens approached within 1 m of me when
I was still for 30 min or longer. Indeed, I once awoke from a nap on the
ground to find a sparrow staring at me about 20 cm from my face!
My close approach to nests (<10m), however, did provoke alarm and
sometimes distraction displays from the parents when they were in the
nest vicinity. If the female was on the nest, she usually ran about 3 m
then flew about 5 m farther away. Presumably these reactions are nearly
the same as those given in response to other "predators." Several times
I simulated identical predator-reaction behavior by placing a mounted
fish crow model 2 m from a seaside nest. The typical response by the
parents was high pitched "seeet calls" interspersed with the "tuck"
call, given while the birds rapidly flitted around in the vegetation
within 5 m of the nest. Three times I saw females give apparent
distraction displays by trailing their wings as they ran away from their
Discussion of Seaside Sparrow Territoriality
Territory types and variation
The seaside sparrow literature indicates that different races, and
populations within races (see Post 1974), may have functionally
different types of territories. These have been described variously as
colonies (Tompkins 1941; Sprunt 1966); areas with separately defended
nesting and feeding areas (Woolfenden 1956, 1968; Worth 1972); grouped
(defended) nesting territories with undefended remote foraging areas
(Post 1974); nest-centered activity spaces ("Type B" of Wilson 1975;
Post 1960); and all purpose breeding territories (mating, nesting, and
feeding; "Type A" of Wilson 1975, Werner and Woolfenden 1983). The
occasional references to seaside sparrows' being "colonial" may be
misleading in that this designation implies the birds had very small
territories, such as those of colonial shorebirds. Although the limited
nesting habitat and the concomitant foraging behavior of some
populations give the appearance of coloniality, seaside sparrow nesting
groups are perhaps better described simply as aggregations.
I have reviewed the literature describing seaside sparrow habits and
have observed populations from Florida to New York. I conclude that
nearly all subspecies and populations exhibit the "all purpose" type of
territoriality. A few populations (e.g. at Post's (1974) Gilgo Beach
study site) exhibited variations of the all purpose type, in that the
birds sometimes foraged out of their territories on undefended areas.
Territories at Cedar Key were of the all purpose type. Occasionally
individuals were seen foraging, unchallenged, on other known
Territory quality and space use
Post and co-workers (Post 1974, 1981b; Post & Greenlaw 1962; Post et
al. 1983; Greenlaw & Post 1985) comparatively studied the
interrelationships of territory size and quality, predation, food
availability, reproductive success, and mating systems of seaside
sparrows on Long Island, New York, and at Cedar Key, Florida. Their
studies reached several conclusions with which I generally concur: Food
seemed not to be a limiting factor in determining territory size;
"Space-use patterns" (i.e. maintainence of territory size, and foraging
on and off the territories) were more influenced by the numbers of birds
attempting to settle into a habitable area than by food availability.
In other studies Post (1974) and Werner (1975) contended that it is
unlikely that territorial spacing limits the population size of seaside
sparrows. They suggested that as the density of birds increases over
the years the territory sizes simply decrease in order to accommodate
more birds. The population size at Cedar Key remained stable throughout
ny study; thus, I did not have an opportunity to support or refute this
hypothesis under the circumstances of increasing population as described
by these authors. Territorial compression either did not occur at Cedar
Key, or if it did occur then the territories must have become maximally
compressed prior to ny study. I conclude this after considering the
findings of my 1963 and 1984 experiments on territorial birds (Chapter
IV). Because I found that non-territorial males did exist, I contend
that territory boundaries and sizes are not necessarily so flexible as
to accommodate all aspiring breeders, as suggested by Post and Werner.
A few bird studies have established an inverse relationship between
territory size and resources (Zimmerman 1971; Seastedt and MacLean
1979). Greenlaw & Post (1985), however, found that the sizes of the
territories they investigated were not correlated with their composite
index of territory quality (which included nesting, food and
cover/protection factors). Furthermore, territory size was not directly
related to volume of vegetation, area of vegetation, or amount of food
on the territory (Post 1980).
Several recurrent conclusions appear in all seaside sparrow
literature describing territorial and feeding behaviors. My
observations on birds at Cedar Key support most of these: Territory
sizes and probably quality vary considerably within and among
populations. Food is seldom if ever a limiting resource, as
convincingly argued by Post et al. (1983). Animals with small
"nest-centered" territories simply forage, unchallenged, off their
territories. Both migratory and non-migratory males tend to establish
their territories in the same locations year after year. Territorial
shifts within a season rarely occur. Birds in dense populations spend
more time involved in aggressive behavior but neither spend less time
feeding nor suffer lower reproductive success as a result of crowding
(Post 1974). Male sparrows are probably not defending areas for the
food value per se, but are rather advertising and defending territories
in order to increase their chances of mating and keeping mates.
Extension of territory definition and function
Kaufmann (1983) stated that territoriality is one form of social
dominance, dominance being defined as priority of access to critical
resources (e.g. food, mates) that increase the fitness of the dominant
individual. Kaufmann further described territoriality as "relative
dominance." Individual A may be dominant to a subordinate, B, while in
A's territory, but not dominant to B when outside of A's territory.
These interpretations of territoriality are more inclusive than the
restricted working definition I gave at the beginning of this section.
They synthesize that traditional, restricted definition of a territory
as "any defended area" with the broader concept of social dominance.
Kaufmann's characterization of territoriality as one manifestation of
social dominance is quite applicable to seaside sparrows at Cedar Key.
The territories were indeed vigorously defended areas, yet a male off
his territory was invariably subordinate in another bird's territory.
Males together on the few areas of the marsh not occupied by territories
did not evidence dominant-subordinate behavior: apparently shared were
food and the rare female affiliations that occurred outside of
territories. Thus no dominance hierarchy or absolute dominance seemed to
As Kaufmann (1963) pointed out, arguments about functions of
territoriality have mostly been concerned with whether a territory
serves as an area to enhance social stimulation, or as an area to allow
resource acquisition. Evidence in support of the former hypothesis,
proposed by Darling (1952), is that some birds clump their territories
even when nearby suitable habitat is available. Considering the
synchronized breeding behavior of seaside sparrows and the observation
that populations do indeed clump their territories, one may concur that
social stimulation is a function of territoriality in these birds.
However, I do not believe this to be the case in the birds I have
observed, for the following reasons.
First, I suggest that clumping is a response to many individuals
having the same gestalt perception of preferred habitat, which
researchers have not been able precisely to identify. Since food is
apparently not limiting, I suspect that the preferred habitat for a male
seaside sparrow selecting and setting up a territory is an area of the
marsh that allows maximum singing display advertisement (i.e. moderately
low vegetation with dispersed singing perches such as tussocks of
Juncus). Singing and being able to be heard while singing are vital to
the fitness of male seaside sparrows, as determined by experiments
described in Chapter IV. Thus, what may initially appear to be suitable
unoccupied habitat may in fact be unsatisfactory for establishing a
song-defended territory. Secondly, I do not believe that social
stimulation is a function of territoriality in seaside sparrows, because
their apparently synchronized breeding behavior can almost always be
directly attributed to weather and other environmental conditions, such
For seaside sparrows at Cedar Key, the possession of a territory
does seem unequivocally to allow the owner priority of access to the
resources contained therein, the most important of these probably being
singing perches, a mate, and a relatively undisturbed mating/nesting
area. Thus the territories of seaside sparrows easily fit the
conventional concept of bird territories' being "defended," areas
exclusively occupied by a relatively dominant male. Also applicable is
Kaufmann's broader characterization of a territory as "a fixed portion
of an individual's or group's range in which it has priority of access
to one or more critical resources over others which have priority
elsewhere or at another time. This priority of access must be achieved
through social interaction" (Kaufmann 1983, p. 9). Because this
definition includes temporal and relative dominance criteria, this
definition more comprehensively characterizes seaside sparrow
VOCALIZATIONS OF SCOTT'S SEASIDE SPARROWS
Seaside sparrows (Ammodramus maritimus) have a vocal repertoire of
distinctive calls and song types. Because these birds are cryptic and
tend to remain low in their densely-vegetated salt marsh habitat, vocal
communication is important in their social behavior. Intergradations and
varying contextual uses of sounds presumably convey different
information to other birds receiving the messages.
Most older seaside sparrow literature is descriptive, and
vocalizations are reported in general and anecdotal behavioral
observations (Kopman 1915; Sprunt 1924; Holt & Sutton 1926; Howell 1932;
Stone 1937; Tomkins 1941; Nicholson 1946; Woolfenden 1956; Norris 1968;
Trost 1963; Worth 1972; Lowery 1974). Relatively recent studies of the
northern seaside sparrow (A. m. maritimus) by Post & Greenlaw (1975)
and of the Cape Sable seaside sparrow (A. m. mirabilis) by Werner &
Woolfenden (1983) include more objective descriptions of calls as well
as songs and associated behaviors. Post & Greenlaw's (1975) detailed
description of the vocal and display repertoire of their Long Island,
New York, population is especially thorough.
In this chapter I describe and discuss the vocalizations of a
Florida population of Scott's seaside sparrow, A. m. peninsuale. I
include more quantitative and conclusive data than in my preliminary
report on Scott's seaside sparrow vocalizations (McDonald 1983c). This
chapter also compares the vocalizations of my study population to those
of northern seaside sparrows described by Post & Greenlaw (1975) and to
those of Cape Sable seaside sparrows described by Werner & Woolfenden
General Methods of Data Collection and Analysis
The project history, study site, and subjects were described in
I recorded vocalizations and described the behavior of the study
population throughout the years 1981-1984. My most intensive field work
occurred during the breeding seasons (late February through mid-June)
when I went to the marsh at least 3 days/week. I also visited the marsh
about once every 10 days during the remainder of the year. During the
breeding season I made the majority of my behavioral observations and
recordings when the birds were most active--from just before sunrise
until about four hours after sunrise. The birds' activity level
increased again moderately about an hour before sunset. The few evening
behaviors and vocalizations I recorded seemed not to differ from early
morning observations, thus I only mention their occurrence in this
chapter. Unless otherwise noted, my quantitative descriptions of
vocalizations and behaviors are for observations taken on mild spring
mornings when the temperature ranged from 18-330 C, there was no
precipitation, and the wind ranged from 0-24 km/h.
Sample Size and General Observation Methods
The total number of marked birds (1981-1984) was 213, including
birds manipulated in 1983-1984. In generalizing about the use of
vocalizations, I considered only data for 91 mated and 11 unmated birds
that I had observed for at least 15 h per season. Detailed analyses
were based on fewer males, as described below. I studied each subject
male at least one hour per week throughout the breeding season. On a
typical morning I observed 1-3 focal males for about an hour (an hour's
"time budget" block), then watched another 1-3 males for the next hour,
and so on up until about 0900. I randomly determined the sequence of
these time budget observation blocks. Thus, all birds received
approximately equal coverage that was representative of the morning
hours. Females were difficult to observe; I described their behaviors
and vocalizations as parts of their mates' time budgets.
During the time budget I dictated all observed behaviors and the
birds' locations on cassette tape. I made most recordings (including
all used for sound analyses and sonograms in this section) with a Sony
TC 150 cassette tape recorder (Mineroff-modified), using a Bell and
Howell "Shotgun" unidirectional electret condenser microphone with
windscreen. I measured the amplitude (in dB) of a singing male 7 m from
me with a Bruel & Kjaer Sound Level Meter (Type 2219) on 5 Apr 1985.
I also used field data forms to record contextual information,
banding records, nest descriptions, territorial boundaries, and other
biological information. Territory maps for the entire population were
drawn in the field at least bi-weekly throughout the breeding seasons.
General Analysis of Notes and Recordings
I transcribed, tabulated, and summarized the behavioral data. I
determined characteristics of tape recorded sounds (e.g. frequency
ranges, length of song) with a Uniscan II FFT Real Time Sonogram
Spectral Display (Model 4600), and prepared sonograms (Fig. III-i
through Fig. III-10) with a Kay Elemetric 7029A Sono-graph using the
wide-band filter (300 Hz) and either the 80-8000 Hz or the 1600-16,000
Hz scale. The specific vocalizations and behaviors I analyzed are
listed in Table III-1.
Detailed quantitative descriptions of vocalizations and other
behaviors were determined from an analysis of 103 time budget hours of
30 mated and territorial best-studied males. I chose time budgets for
analysis based on comparability of day of year (Apr-May), time of day
(sunrise-0900), and the typical mild weather conditions described above.
I used non-parametric statistics (Siegel 1956; Conover 1980) for the
My specific methods of investigating flight songs ("complex flight
vocalizations" of Post & Greenlaw 1975) and countersinging are discussed
in separate sections below.
Table III-1. Vocalizations and behaviors measured during time budget
observations (in min and sec duration, and frequency)
Not matched countersinging
Other Vocalizationsa ,b
Zuck and other calls
When not singing
Singing, song type change
Singing, no song type change
Singing, stop singing
Observations Relating to Females
Female solicitation calls, other calls
Females building nests
Other behaviors related to females and young
Feeding, resting, and preening
Off territory: feeding; invading nearby territory
Reactions to Intrudersa,b
Frequency, duration, and location of intruder
Solo primary song Sham-preen
Whispering song Bob and bill jab
Calls (as above) Contact
a Contextual information also noted: bird's identity, location, mated
status; presence of conspecifics, date, weather, and location of
bTerminology follows Post & Greenlaw 1975.
Results and Discussion of Calls and Song
Descriptions and Use of Vocalizations
Scott's seaside sparrows make 14 distinct vocalizations: a primary
song, three modifications of the primary song, and 10 calls. The
probable functions of their songs and calls are summarized in Table
III-2. I distinguish "songs" from "calls" as implicitly defined by most
ornithologists, and as specifically stated in Pettingill's working
definition: "Song is a vocal display in which one or more sounds are
consistently repeated in a specific pattern. It is produced mainly by
males, usually during the breeding season. All other bird vocalizations
are collectively termed call notes or, simply, calls" (Pettingill 1970,
p. 319). I use Post & Greenlaw's (1975) vocalization terminology
throughout, except for "whispering primary song," which is from Werner &
Table 111-2. Vocalizations of Scott's seaside sparrows
Tsip call and
1, 2, 4
1, 2, 5
Male and Female;
Male and Female;
Male and Female;
1, 2, 5
Male and Female;
1, 2, 4
Male and Female;
Male and Female; 3
(given by young
Territory defense and
Territory defense and
chase; nest defense
attack; nest defense
Proclaim location of
Flocking (fall & winter)
chase; female: nest area
distraction, proclaim sex
Attract males for
chase; drive off young
Extreme distress call
Begging for food
aTerminology follows Post & Greenlaw (1975). This table is modified
from Post & Greenlaw's (1975) Table 3, which summarized "vocal
displays" of northern seaside sparrows.
bcontexts in which the vocalization were elicited: 1-in presence of
intruder or neighbor bird; 2-in presence of mate; 3-in presence of
predator, or human disturbance; 4-also given when bird apparently alone;
5-given in flight.
Calls of Scott's seaside sparrows
In this section I give sonograms, descriptions, and suggested
functions of 10 calls, presented in approximate order of their frequency
of occurrence during the breeding season.
The "tuck" (Fig. III-1A) was the most common of the calls. It was
given by males and females throughout the year. The short tuck covers a
wide frequency range and is probably the same call Werner & Woolfenden
(1983) labeled as the "chip" call for Cape Sable seaside sparrows. The
tuck appeared to be an all-purpose vocalization, but seemed to function
mostly as a general alarm and moderately intense aggressive call. It
was invariably given during short-distance aggressive interactions and
usually accompanied by wing and tail flicks, and by the "tsip" calls
(shown specifically in Fig. III-1A).
Males gave tuck calls at an average rate of 0.3 min/h when there was
no apparent disturbance on their territories. During intrusions,
however, the tuck rate increased to 13.5 min tucking/h intruder present.
This call was also given alone (or together with "tsips") by both
parents when a predator or human approached a nest within 5 m. The tuck
call was the only one I heard regularly during the non-breeding season.
I also heard fledglings and juvenile birds give this call.
Tsip and si twitter
Both males and females also gave the higher-pitched, short "tsip"
call (Fig. III-1B). When birds were highly agitated the "tsip" was
rapidly repeated, thus intergrading into the "si twitter" call. The
"tsip" was often interspersed with "tuck" calls, as mentioned above, and
was accompanied by wing and tail flicks. During bouts of calling, which
lasted 0.25 to 17.3 min, birds gave "tucks," "tsips," and combined
"tuck-tsips" at a rapid and usually regular rate of 30-145 calls/min.
As with the "tuck" call, "tsips" and "si twitters" generally signaled
alarm and aggression, but more often indicated a higher level of alarm.
My closest approach to nests (<2 m) and my placing of a stuffed fish
crow near nests nearly always elicited "si twitters." I never heard
"tsips" or "si twitters" from undisturbed birds. During intrusions the
average combined "tsip-si twitter" rate was 4.5 min tsip-si twitters/h
intruder present. I only rarely heard the "tsip" call during the
non-breeding season, and I never heard fledglings or juveniles give
either of these calls.
During the breeding season I occasionally heard females give a soft,
high-pitched "seeep" call Fig. III-1C). Most of the "seeeps" occurred
during bouts of copulation. Sometimes a female gave this call as a
nearby male began to sing relatively softly (Fig. III-2A). Post &
Greenlaw (1975) suggest that the "seeep" call conveys a weak fear
message. This call, or a very similar one, was the second most common
vocalization I heard outside of the breeding season. Males and females
of both Scott's seaside sparrows and wintering sharptail sparrows at
Cedar Key gave "seeeps," especially in the late fall and early winter. I
agree with Post & Greenlaw (1975), and with Werner & Woolfenden (1983),
that this call probably functions as a social and flocking vocalization
outside of the breeding season.
The loud and relatively short "tchi" call (Fig. III-2B) was given by
both sexes and was most often heard during chases. About half of the
total thisi" I heard were given during or immediately following chases.
Usually the thisi" were rapidly repeated, and frequently they
intergraded with a slower, slurred "tyu." The "tyu" itself often slurred
into a "whinny"-like vocalization (described below). The "tchi" call
was probably the same as the "squeaz" call described by Werner &
Woolfenden (1983), and the same as the "jee-jee-jee-jee-jee-jeeeu-jeeeu"
call described by Norris (1968).
The primary function of this call seemed to be signalling general
aggression during chases. Frequently, however, I heard females give
rapid thisi" in flight ("tchi flight") as they left a nest they were
building or incubating, even though no threatening bird seemed to be in
the vicinity. These nest-departure thisi" were not given adjacent to
the nest, but rather at about 10-15 m from the nest. During a 1 h
observation of nest building in early May 1983, for example, I saw a
female depart and come into her nest 18 times. Fifteen of her
departures were accompanied by thisis" but only one arrival was
accompanied by this call. Jon Greenlaw (pers. comm.) reports that female
northern seaside sparrows behave in a similar manner. I suggest,
therefore, that the "tchi" also functioned as a distraction call by
drawing a potential predator's attention away from the nest as a female
departs. Jon Greenlaw (pers. comm.) also thinks that thisi" in the
nest vicinity function to let the resident male know that this departing
and arriving bird is a female who belongs, rather than an invading male.
Other than the females giving the "tchi" as described above, I
seldom heard this call when no intruders were present (0.11 male
tchis/non-intrusion hour). It was difficult to quantify the "tchi" rate
during intrusions. On the average, however, a territory owner spent
2.62 min chasing/h intruder present. I estimate that at least half of
these chases were accompanied by rapidly repeated thisis" most of these
calls given by the owner.
I heard only females give the "whinny," with one unusual exception
described below. This whirling, quavering call varies in rate from 0.3
to 3/sec (Fig. 111-3). The whinny was the female's solicitation call;
it functioned to attract a male. Females gave this call more often when
a male was relatively close to her (within about 7 m), and especially if
the male was singing. Males were immediately attracted to the "whinny"
vocalization, and copulation usually followed. Even though females gave
the "whinny" from on or near the ground, males seemed to have had no
problem finding the vocalizing females. It is likely that some auditory
characteristics) of this vocalization made it easy to locate.
Females gave this call most often prior to, and during nest
building. Because females usually initiated up to 5 clutches per
breeding season, the overall intensity of "whinnies" heard for the
population remained the same from late March through May. The average
whinny rate heard on all territories during these months was 2.02 min
Post & Greenlaw (1975) describe the postures associated with the
"whinny" vocalization and copulation. Werner & Woolfenden (1983) do not
describe a female solicitation vocalization.
I only once heard a male give a distinct "whinny" (as opposed to the
"whinny"-like "tyu," described above). On 6 May 1984 a male invading an
experimentally muted bird's territory repeatedly gave whinnies while he
The loud, raspy "zuck" (Fig. 111-4) was an aggressive call given
during intense fights. Most of the zucks I heard were given by males,
but sometimes females and juveniles gave this call. It may have been the
same as the "Shu-shu...shu" call of Cape Sable seaside sparrows that
Werner & Woolfenden (1983) mention but do not describe. In addition to
its functioning as a general, high intensity aggressive call, "zucks"
were the vocalizations most often given by fathers when they drove their
older, almost independent fledglings off their territories (about 2-3
weeks post-fledging). Other than these father-fledgling encounters, I
never heard this call given during non-intrusion circumstances. During
intrusions both territory owners and intruders gave "zucks" (often mixed
with thisis) at the rate of 0.7 min zuck/h intrusion.
The "Scree" (Fig. 111-5) was a harsh distress call I heard only
(with a few rare exceptions) from a few birds trapped in mist nets and
being handled. Both sexes of adults and juveniles gave this call.
The monotonous and insistent "Begging Calls" (Fig. 111-6), given by
older nestlings and fledglings, were heard most often towards the end of
the breeding season. Nestlings gave "Peep" (Werner & Woolfenden 1983)
and "Chup" (Post & Greenlaw 1975) calls.
Post & Greenlaw (1975) describe one further call I have not
mentioned--the "Chew" call. To my knowledge, I never heard this call at
Cedar Key. Jon Greenlaw (pers. comm.) proposes that the "Chew" call is
probably a modified "tchi-whinny" vocalization.
z i H-
Figure 111-2. (A) Audiospectrogram of Male Primary song and concurrent
female Seeep note (indicated with "X"). (B) Audiospectrogram of Tchi
' I I I
TIME IN SECONDS
TIME IN SECONDS
___ i, ]
^ ^" -^
--- ^r ^ '
-.-------------------.--.-----~-.-----.------------------- I -
I I I I
Aw-^i^ '^s. '"^
co e 0
I I I
I I I I
SI l I I I 0
co -0 C 0
I I I I
Figure III-9. Audiospectrograms of Countersinging from two males,
individuals A and B.
a Ua~ bj. 'a
TIME IN SECONDS
TIME IN SECONDS
I I I
Audiospectrogram. The seaside sparrow primary song (Fig. 111-7) is
relatively simple. The introductory portion of rapid clicks (centering
around 6.5 kHz) is immediately followed by a buzzy trill (centered
around 3.8 kHz). These frequency ranges and the song duration of about
1.0 second were characteristic for the entire population.
General description of singing behavior. During my study, only
males sang. Although Post & Greenlaw (1975) describe "female songlike
vocalization" that resembles male song, I never heard a vocalization of
this type at Cedar Key. Aales sang to delineate territories and to
attract females. Experimental evidence for these functions of song is
given in Chapter IV.
Males usually sang from elevated perches, such as tussocks of
Juncus. Most birds had 3-7 favorite singing perches within their
territories from which they gave about 35% of their songs. From
1979-1984 only two males sang from grid marker stakes, although Post &
Greenlaw (pers. comimi.) found that birds in their dense study population
often sang from grid markers.
The singing pattern of seaside sparrows is similar to that of many
song birds (Table 111-3). Birds sang in "discontinuous" patterns of song
"bouts" (songs repeated continuously without a pause), of "eventual
variety" (song type change after three or more repetitions of the same
song type) (Hartshorne 1956; 1973). An average bout throughout the
season consisted of 19.2 songs and lasted 1-5 min (mean = 1.62). Highly
variable periods of silence (mean = 7.9 min) separated song bouts. Males
changed perches during 17% of these between-bout silences, before
resuming singing. Song rate within a bout ranged from 6-9 songs/min
Table 111-3. Characteristics of solo primary singing and countersinging
of 30 mated male Scott's seaside sparrows during April and May
Song (Solo) Countersong b
Characteristics Total Total Matched Not Matched
N (bouts) 391 223 143 80
Mean bouts/h obs. 3.80 2.17 1.39 0.73
Total min sing 635 631 438 192
Mean min sing/h obs. 6.16 6.13 4.26 1.86
Mean min song/bout 1.62 2.83 3.07 2.40
Total bouts edgec 198 123 30 43
Total bouts center 117 41 26 15
Total min edge 315 369 275 94
Total min center 193 110 66 44
Mean song type <0.01 0.02 0.02 <0.01
Mean song type 0.32 0.33 0.47 0.29
Mean perch 0.97 0.33 0.31 0.35
Mean perch changes/ 0.16 0.02 0.02 0.01
Mean perch changes/ <0.01 <0.01 <0.01 <0.01
bout with song switch
Mean perch changes/ 0.03 0.02 0.02 0.01
bout without switch
Mean perch changes/ 0.13 0.05 0.01 0.02
bout, song cessation
Table 111-3, continued.
Characteristics of solo primary singing and countersinging determined
from analyses of 103 h of time budget observations, when no intruders
were present on focal birds' territories. Other conditions during time
budget observations are described in the text.
bRate values calculated for Matched and Not Matched columns based on
number of bouts and minutes of Matched and Not Matched singing,
respectively. Thus the sums of rates of Matched and Not Matched values
do not add up to the Total column for Countersong.
Edge defined as the outer-most 10 m of the bird's territory.
dCenter defined as the area within a 25 m radius of the estimated center
of the bird's territory.
(mean = 7.7), close to the 6.6 song rate Woolfenden (1956) reported for
New Jersey birds, and slightly lower than the 10.6 song rate reported by
Post & Greenlaw (1975).
Individual males had a repertoire of two to four similar song types
(mean = 2.41). When both solo singing and countersinging, birds seldom
switched song types within or even between song bouts. The mean rate of
song type switches during a bout was about 0.01/bout. Thus their
singing was extremely "monotonous," sensu Hartshorne (1956; 1973),
because their singing pattern was both continuous and of low
"versatility" (infrequent song type changes).
Most males shared their song types with nearby territorial birds. A
few of the birds had one highly distinctive song type within their
repertoire that enabled me to recognize individuals aurally from as far
away as 150 m. I did not detect any tendency for males to have a
preferred song type from within their small song repertoire.
Seaside sparrows at Cedar Key seldom began a new song type after
moving to a new perch while singing (Table 111-3). Of a total 67
incidents of perch changes during singing, there was only one concurrent
song type change. This constrasts with Krebs's (1977a, 1978) "Beau Geste
hypothesis" that territorial birds switch song types when changing
perches, thus possibly giving potential intruders the impression that
territories are saturated.
Influence of abiotic factors on singing behavior. Singing activity
varied throughout the year. It was most intense relatively early in the
breeding season (late March through mid-April), especially before and
just after birds were mated. The average time singing of 29 males
measured 1-15 Apr 1983 was 19.4 min singing/h. In the third week of May
their song rate decreased to 12.1 min singing/h, a significant
difference (two-tailed Wilcoxon matched-pairs signed-ranks test, T=2,
Weather modified the intensity of singing, on both a daily as well
as a seasonal basis. Very early in the spring (February through mid
March) birds sang more as the day warmed slightly, up to about 200 C.
During the middle and especially towards the end of the breeding season,
birds sang less as the day warmed. Virtually all singing stopped at
temperatures above 320 C, regardless of the time of day. From the middle
of the breeding season till the end, birds sang more on cloudy, cool
mornings. Light rain also enhanced singing activity at this time of the
year, and even heavy rain and thunder and lightning dampened singing
activity only slightly. Brisk winds (>25 km/h), however, greatly
reduced singing activity, especially early in the season on cool days.
The intensity of singing activity also varied throughout the day.
Peak song activity was early in the morning, from sunrise to about 3
hours after sunrise. The earliest I heard singing was 20 min before
sunrise. Birds also sang in late afternoon until about one-half hour
after sunset. Compared to seaside sparrows on Long Island, New York,
that I observed in June 1982, birds at Cedar Key sang less in the
evenings. The first morning and last evening songs were similar to
songs given during peak morning activity, except the song rate
(song/min) within the bout was lower very early and late in the day.
Influence of other birds on singing behavior. Unmated males sang
significantly more bouts than mated males, and thus their total time
singing (21.4 min/h) was greater than that of mated males (12.3 min/h),
as measured in May (two-tailed Mann-Whitney U-test, N=30 and 11,
P<0.01). Singing rate also differed significantly according to whether
an intruding male seaside sparrow was present. After territories were
well established (by mid-April), intrusions were rare (mean = 0.7 min
intrusion/hour). When an intrusion did occur an owner's first reaction
was increased singing, and this was often successful in repelling the
intruder. If the intruder was not driven off by normal primary song,
territory owners switched to short-distance and more aggressive
vocalizations and behaviors--whispering primary songs, tuck and si
twitter calls, chases, quivering wing raises, and (rarely) contact
The "whispering primary song" (Werner & Woolfenden 1983) was a
slowly delivered (mean=3.5 song/min), low amplitude, and slightly lower
pitched modified primary song. It was usually given by a male perched
near the ground and confronting an intruder at 1-5 m. The whispering
primary song was delivered with an almost closed beak, in contrast to
the normal primary song where the bird threw back his head and opened
his beak wide as he sang. I do not have data describing reactions of
males that heard these whispering songs. Because I only heard it during
agonistic encounters, this vocalization may have functioned to transmit
a message of threat and likelihood of attack. Jarvi et al. (1980)
described a similar use of modified primary song in the willow warbler
(Phylloscopus trochilus) that transmitted a message that the singer was
likely to attack his opponent.
Because short-distance encounters were more often accompanied by
calls and displays, the combined normal and whispering primary song rate
during intrusions (2.4 min song/h intrusion) was much lower than the
song rate when no intruder was present (12.3 min song/h non-intrusion).
Calls of most other marsh birds, including the raucous clapper
rails, seemingly had no effect on the seaside sparrows' vocalizations or
other behaviors. Seaside sparrows did respond antagonistically toward
vocalizing sharp-tailed sparrows (Ammodramus c. caudacuta) when these
wintering migratory birds began singing prior to their departure the
first week in May.
Young males sang rudimentary subsong late in July and in August
(Fig. 111-8). These songs consisted of garbled warbles and parts
(usually the terminal trill) of the adult primary song. Subsong was not
as loud as the primary song and was sung only sporadically instead of in
bouts. These first song attempts improved and came to resemble the
adult's primary song by late fall, when virtually all singing activity
stopped. Both yearling and adult males began to sing again in late
February, and songs of the first year birds could still be
differentiated from those of older birds. By mid-March, however, songs
given by first-year and older birds could no longer be distinguished.
Countersinging and Repertoire Use
Introduction and comments
Countersinging occurs when two, three, and sometimes four male birds
alternate their songs in a regular pattern. Countersinging is described
as "matched" when the same song type or types are sung by the
participating birds. The behavioral and evolutionary significance of
song repertoire sharing in general, and of song matching during
countersinging in particular, has been the subject of recent stimulating
studies (Krebs & Kroodsma 1980; McGregor et al. 1981; Payne 1982; Kramer
et al. 1985; Searcy et al. 1985).
Many relatively simple explanations for song matching exist:
Matching indicates high-intensity interactions (Lemon 1968b). Birds
match in order to monitor the positions of their neighbors (Lemon
1968a). Relative dominance between countersinging birds influences the
degree of matching (Kroodsma 1979). Time intervals between songs of
countersinging birds indicate which of the participants is dominant
(Smith & Norman 1979). Matching functions as a vocal threat that
regulates distance between birds (Todt 1981). Matching is a graded
signal used in territorial encounters (Krebs et al. 1981). Finally,
matching indicates readiness to interact aggressively (Horn & Falls
Further interpretations of song sharing that deal more generally
with repertoires and repertoire sharing (which may or may not involve
matched countersinging) are: Larger song repertoires make recognition
of neighbors more difficult (Falls & d'Agincourt 1981; Searcy et al.
1981). Larger repertoires are more attractive and stimulating to
females (Howard 1974; Searcy et al. 1982). Larger repertoires allow
resident birds to fool potential intruders through increasing the
perceived density of singing birds (Krebs 1976), and, young indigo
buntings (Passerina cyanea) mimic the repertoires of older territorial
males and thus deceive other males through mistaken identity (Payne
1982). Searcy et al. (1985) found no correlation between song repertoire
size and male "quality" in song sparrows (Melospiza melodia).
While these may or may not be adequate explanations for song sharing
in birds, some recent experiments on song sharing have become
increasingly sophisticated. These studies have incorporated more
objective methods of determining song similarity, the possible effect of
sound degradation from sender to receiver influencing behavior, the
birds' natural use of their repertoire, and their familiarity with
neighboring males (Falls et al. 1982; Schroeder & Wiley 1983b; Whitney &
Almost all investigations of song matching and repertoire use have
involved playback experiments and measures of response strength to the
tape recorded songs. Ideally, field studies to determine the occurrence
and significance of song sharing (without using controlled playback
experiments) would be on birds with only one or two songs in their
repertoires. Usually, though, this is not the case. Therefore a major
design consideration in natural observational investigations is first to
make comprehensive studies of normal singing behavior of undisturbed
birds. That is, the song repertoires (and the possible differential use
of songs from within the repertoires) of all subjects must be thoroughly
analyzed, and the probabilities that each bird will sing a given song in
different circumstances determined. Simply describing the composition of
the bird's repertoire is not adequate.
Studies of the birds' natural use of song types are complicated by
additional considerations. The observer's method of determining degree
of song similarity may greatly influence the results. Also, some birds
are known to use different song types according to: location within
their territory (Lemon 1968b; Lein 1978; Schroeder & Wiley 1983a),
whether a male or female is present (Smith et al. 1978; Schroeder &
Wiley 1983b), distance from rival conspecifics (Simpson 1985);
familiarity with the neighboring male (Wunderle 1973; Falls et al.
1982); similarity of rival male's song to self song (McArthur 1986),
rate of song type switching (Simpson 1985), acoustic degradation over
distance (Morton 1982; McGregor et al. 1983); overall aggressive
motivation (Lein 1978; Schroeder & Wiley 1983a); and stage in breeding
(Falls & Brooks 1975; Petronovitch et al. 1976). Furthermore, three
recent studies have shown that the intensities of agonistic interactions
were not correlated with the choice of song types per se, but rather
with the rate of song type switching alone (Kramer et al. 1985; Simpson
1985) or together with the degree of matching (Horn & Falls 1986).
Thus, what may appear to be unambiguous results from studies of how
birds use their repertoires, including song matching during
countersinging, should be carefully evaluated. Some recent studies
have, however, more scrupulously investigated countersinging and song
type use in general based on detailed analyses of repertoire composition
and contextual use (McGregor & Krebs 1982; Schroeder & Wiley 1983a,
1983b; Simpson 1984, 1985.; Lemon et al. 1985).
The purpose of these introductory remarks is several-fold. First, a
field study seeking to describe and interpret the function of repertoire
sharing and countersinging is likely to be more complicated than is
intuitively obvious. The design must consider many variables that may
be difficult, if not impossible to control. Secondly, I introduce this
section on the countersinging of Scott's seaside sparrows with these
remarks in order that the reader may realize why I present only
descriptive summaries rather than the testing of the significance of
repertoire sharing and matched countersinging.
Methods of investigating repertoires
When birds countersang during time budget observations, I noted
whether they matched or not, in addition to taking my standard singing
behavior measurements (bird's identity, presence or absence of
intruders, time singing, perch changes while singing, and incidence of
song type switching). As described in the "General Methods," I
tabulated in detail 103 time budgets (selected for comparability of
date, weather, absence of intruder, etc.) for 30 mated males observed
Results and discussion of repertoire use
I measured parameters of solo primary and countersinging activity of
Scott's seaside sparrows (Table 111-3). The mean total singing activity
(solo singing and countersinging) for males was 12.29 min song/h.
Two to four males often participated in bouts of countersinging, the
alternation of songs separated by 3-8 sec (Fig. 111-9). The pattern of
song alternation was usually regular, but in 3% of the countersingng
bouts the alternating songs drifted out of phase and began to overlap.
Countersinging comprised about half of the total singing time.
Approximately two-thirds of the total countersinging time was matched
countersong (Table 111-3).
The mean song repertoire size of the 30 males was 2.41
songs/bird/season. I did not measure the proportional use of song types
within repertoires, nor did I measure the degree of repertoire sharing
within the population.
Some conclusions are apparent from the data presented in Table
111-3, even without statistical testing. First, apparently neither solo
singing nor countersinging was preferred in the several contexts
analyzed. That is, countersinging did not seem to be used
proportionately more often than solo singing at territory edge, nor did
perch and song type switches seem to be correlated more or less strongly
with countersinging. The same lack of differential patterns according
to context seemed to exist when comparing matched to non-matched
countersinging. A possible exception is that birds may have sung more
minutes of matched song than non-matched song at territory edges.
Of course more comprehensively analyzed data are needed before
statistically valid statements regarding repertoires and countersinging
in seaside sparrows can be made. I do, however, conclude the following
at this time. First, countersinging is a form of vocal "duelling" that
indicates a slightly elevated aggressive or aroused state. That is,
countersinging is a graded signal in seaside sparrows, but probably a
less strongly graded signal than in most birds. Second, song matching
while countersinging and repertoire sharing in general in these birds
are probably chance events, analogous to the "epiphenomena" of song
pattern variety suggested by Wiens (1982) for sage sparrows (Amphispiza
belli). Songs of seaside sparrows may be observed to match simply as a
consequence of their small repertoires of simple and similar songs,
their low population turnover rates, and their sedentary habits.
Flight Songs: Description and Comparison to Perch Songs
An early Florida naturalist, Donald J. Nicholson aptly
characterized seaside sparrow singing: "Towards the end of March the
marshes are fairly buzzing with the purring, wheezing songs...He tries
one perch and seeks another fifty or seventy-five yards away flying low
over the rank growth. Every so often he fairly 'explodes' with passion
leaving his concealment to rise on fluttering wings sixty or seventy
feet above the marsh uttering his erratic little song as he goes up and
down dropping out of sight in the salicornia" (Nicholson 1946, p. 41).
The flight song (Fig. III-10), accompanying the flight song display,
is a combination of preliminary calls followed by the primary song. This
vocalization and display of about 3-4 sec is sporadically given by males
throughout the breeding season. It begins with introductory
high-pitched "si" calls, followed by lower-pitched "tuck" calls, and
ends with one or two condensed versions of the primary song. The buzzy
trill of the primary song portion is about 0.4 sec shorter than the
trill of the normal primary song. The introductory calls vary in
duration and type, but are always given on the ground and during the
bird's ascent to about 10-15 m. The primary song is uttered as the bird
descends. Woolfenden (1956), Trost (1968), Post & Greenlaw (1975), and
Werner & Woolfenden (1983) also describe singing and flight songs of
Methods of investigating flight song activity
My observations of Scott's seaside sparrows during the breeding
seasons of 1981-1982 suggested that overall song activity seemed to be
affected by whether the birds were mated, and by time of day, time of
year, and weather. In most Passerines these factors do influence the
intensity of primary song singing from a perch (hereafter designated in
this section as "perch singing"). I measured and compared perch song
and flight song activities of my study population during the early
breeding season of 1982. Then I tested whether the above factors
differentially affected flight song activity (as compared to perch
singing) by comparing the relative frequencies of flight songs to perch
singing under specified conditions described below.
I sampled the overall singing activity of 28 males during 31 field
days from 12 Feb-26 Apr 1983. Throughout the day I monitored flight
song and perch song activity within one hour time blocks from pre-dawn
through mid-afternoon. The time blocks were designated in hours
relative to sunrise: the first hour block of a day began 15 min before
sunrise, the second hour block began 45 min after sunrise, and so on. I
randomly chose and timed the perch singing of a different male during
each hour block. Simultaneously, I counted all flight songs heard within
100 m during the hour. As I counted and timed songs during each hour
block, I also noted wind velocity, temperature, the singing bird's
location, and identity and mated status (if known).
In summarizing my data, I defined an hour's "flight song activity"
as the average number of flight songs heard within the 100 m radius
during the hour. I defined "perch song activity" as the average number
of minutes the randomly chosen birds sang during the hour within the
same 100 m. Then, for every level of increment of the variables being
investigated (e.g. for temperature category 5-9 C), I tabulated flight
song activity (FS), perch song activity (PS), and a calculated FS/PS
ratio. A statistical analysis using multiple regression would have been
the ideal method of exploring these data. Yet because some data were
ordinal rather than interval and normality was not assumed,
non-parametric statistical analyses were required. In order to validly
consider the effect of only one variable at a time, I chose subsets of
data, as described below for each analysis. I used Spearman rank
correlation (Siegel 1956) to determine if PS, FS, and FS/PS ratios were
correlated with day of year, time of day, temperature, and wind
velocity. I tested significance of the correlation coefficient at the
two-tailed P<0.05 level. I also compared FS and PS activities of mated
and unmated birds with a two-tailed X one-sample test (Siegel 1956).
Results of singing activity analysis
Males sang perch songs at an overall rate of 17.1 (SE=5.9) min
song/h. Flight song rate varied considerably among males. The mean rate
was 0.15 flight songs/male/h. The rates of perch songs, flight songs,
and FS/PS ratios did, however, vary significantly as detailed below.
Four variables correlated significantly with both perch singing and
FS/PS ratios: day of year, time of day, temperature, and wind velocity.
Mated and unmated birds differed significantly in the number of flight
Day of year. I analyzed the following subset of data to determine
the correlation of singing activity with day of year: 88 h of
measurements for unmated birds taken on 19 days when the temperature was
15-24o C and the wind was <24km/h. I found that perch song activity
increased significantly (r=0.72), and FS/PS ratios (r=-0.81) decreased
significantly as the breeding season progressed, up until the last week
of April. Flight song activity considered alone, however, did not
correlate significantly with day of year (r=-0.01).
Time of day. I determined the effect of time of day by considering
the same subset of observations: 88 hours of measurements for unmated
birds noted when the temperature was 15-24 C and the wind was <24km/h.
I found perch song rate was greatest just after sunrise and declined
significantly (r=-0.95) as the day progressed (excluding evening
singing). Flight song activity remained about the same all day,
although the FS/PS ratio increased significantly (r=0.33) through the
day (Fig. III-ll).
Wind. I analyzed the following subset of data to determine the
effect of wind: 79 morning hours (hour blocks 1-5) of measurements for
unmated birds noted when temperatures were 15-24 C. I found that brisk
winds had a definite dampening effect on perch song activity (r=-0.97)
but no significant effect on flight song activity. The FS/PS ratio
increased significantly (r=0.88) as wind velocity increased (Fig.
Temperature. To determine the influence of temperature, I
considered 77 hours of observations made on unmated birds, during hour
blocks 1-4, and when the wind was <24km/h. I found that cooler
temperatures significantly (r=0.88) decreased perch song activity but
had no significant effect on flight song activity. The FS/PS ratio did
significantly decrease (r=-0.83) as temperature rose (Fig. 111-13). In
other words, as with high winds, birds gave proportionally more flight
songs in cooler weather.
Mated status. I considered the singing activity of 23 males before
and after they were mated. The time elapsed between measurements was
8-19 days. I observed birds for 73 h during hour blocks 1-4, when
temperatures were 15-24o C and the wind was <24km/h. Males sang less
(14.9 min/h) after they were mated than before mated (19.7 min/h), but
this decrease in singing may have been at least partially due to the
seasonal decline in singing activity described above, or vice versa.
From a sample of 122 flight songs, 74 were given by birds of known
mated status. Unmated birds sang 84% of these 74 flight songs (Fig.
111-14). This difference was highly significant (two-tailed X2
one-sample test, X2=33.8, df=1, P<0.001).
Discussion of flight songs
Flight songs are characteristic of birds that live in open
grasslands or tundra. Many emberizine sparrows, including the
congeneric seaside, sharptail, Baird's (A. bairdii), and Le Conte's
sparrows (A. leconteii), have well-developed flight songs.
Why do seaside sparrows give flight songs? Although the flight song
is a highly conspicuous vocalization, obviously its energetic cost is
greater than that of perch singing. Post & Greenlaw (1975) report that
in their migratory northern seaside sparrows, flight songs are much
more common soon after females arrive on their male's territories. This,
as well as my findings that unmated Scott's seaside sparrows gave more
flight songs than mated birds, suggests that flight songs may be used in
mate attraction. All seaside sparrows, however, continue to give these
vocalizations throughout the breeding season.
A major portion of the flight song vocalization is the uttering of
one or two modified primary songs. Elsewhere (Chapter IV) I have shown
experimentally that the primary song is essential for both mate
attraction/retention and territory establishment/retention. Thus, it is
reasonable to assume that flight songs can effect the same critical
functions. I have presented evidence that birds give relatively more
flight songs (and sometimes they give only flight songs) during
inclement weather and when unmated. I therefore suggest that even
though they may be energetically costly, flight songs so effectively
magnify the message of the primary song that they are worth more to the
male, especially under otherwise adverse singing conditions.