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Full text of "North American fauna"

BOSTON PUBLIC LIBRARY 



3 9999 06317 642 2 



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NATURAL HISTORY 

OF THE 

SWAINSON'S WARBLER 




NUMBER 69 



UNITED STATES 

DEPARTMENT OF THE INTERIOR 

BUREAU OF SPORT FISHERIES AND WILDLIFE 



•>r 



NORTH AMERICAN FAUNA 

This publication series includes monographs and other reports of scientific 
investigations relating to birds, mammals, reptiles, and amphibians, for pro- 
fessional readers. It is a continuation by the Bureau of Sport Fisheries and 
Wildlife of the series begun in 1889 by the Division of Ornithology and Mam- 
malogy (Department of Agriculture) and continued by succeeding bureaus — 
Biological Survey and Fish and Wildlife Service. The Bureau distributes 
these reports to official agencies, to libraries, and to researchers in fields 
related to the Bureau's work; additional copies may usually be purchased 
from the Division of Public Documents, U.S. Government Printing Office. 

Reports in North American Fauna since 1950 are as follows (an asterisk 
indicates that sale stock is exhausted) : 

*60. Raccoons of North and Middle America, by Edward A. Goldman. 1950. 
153 p. 

*61. Fauna of the Aleutian Islands and Alaska Peninsula, by Olaus J. 
Murie; Invertebrates and Fishes Collected in the Aleutians, 1936-38, 
by Victor B. Scheffer. 1950. 406 p. 

*62. Birds of Maryland and the District of Columbia, by Robert E. Stewart 
and Chandler S. Robbins. 1958. 401 p. 

*63. The Trumpeter Swan; Its history, habits, and population in the United 
States, by Winston E. Banko, 1960. 214 p. 

*64. Pelage and Surface Topography of the Northern Fur Seal, by Victor B. 
Scheffer. 1961. 206 p. 

65. Seven New White-winged Doves From Mexico, Central America, and 

Southwestern United States, by George B. Saunders. 1968. 30 p. 

66. Mammals of Maryland, by John L. Paradiso. 1969. 193 p. 

67. Natural History of the King Rail, by Brooke Meanley. 1969. 108 p. 

68. The Sea Otter in the Eastern Pacific Ocean, by Karl W. Kenyoh. 1970. 

352 p. 

69. Natural History of the Swainson's Warbler, by Brooke Meanley, 1971. 

90 p. 



NATURAL HISTORY 
OF THE 

SWAINSON'S WARBLER 



by Brooke Meanley, Wildlife Biologist 

Patuxent Wildlife Research Center 
Division of Wildlife Research 
BUREAU OF SPORT FISHERIES AND WILDLIFE 




NUMBER 69 



m BOSTON PUBLIC LiBRARY 
GOVERNMENT OOCUMENTS OEPARTMENT 
RECEMED 




UNITED STATES 
DEPARTMENT OF THE INTERIOR 

FISH AND WILDLIFE SERVICE 
BUREAU OF SPORT FISHERIES AND WILDLIFE 




North American Fauna, Number 69 

Published by 

Bureau of Sport Fisheries and Wildlife 

February 1971 



U.S. GOVERNMENT PRINTING OFFICE 
WASHINGTON : 1971 



For sale by the Superintendent of Documents, U.S. Government Printing Office 
Washington, D.C. 20402 - Price 50 cents 



Contents 



Page 

Introduction 1 

Methods 2 

Acknowledgements 3 

History 5 

Distribution 13 

Breeding Range 13 

Atlantic Coastal Plain 13 

Gulf Coastal Plain 15 

Southern Appalachians 17 

Ozark Mountains . 19 

Piedmont Province . 19 

Extralimital records (United States) 19 

Winter Range 20 

Cuba -20 

Jamaica 20 

Swan Islands 20 

Mexico 21 

British Honduras 21 

Migration 22 

Spring 22 

Fall 23 

Ecological Relations 25 

Coastal Plain 26 

Ocmulgee River floodplain forest in Georgia 30 

The Great Dismal Swamp 33 

Bayou Boeuf Swamp, La., and Monkey John 

Swamp, S.C. 35 

Western Kentucky 36 

Southern Appalachians . 36 

Allegheny Plateau in West Virginia 39 

Toxaway River Gorge 41 

Description '_ 43 

Size 43 

Distinguishing characters 44 

Adult plumage 44 

Juvenile plumage 45 

Geographic variation 45 

Molting 45 

Breeding Biology 46 

Territorial behavior 46 

Arrival on the breeding grounds 46 

Homing 46 

Territories 47 



iv CONTENTS 



Page 



Defense of territories 50 

Courtship and mating 51 

Vocalizations 52 

Pouncing 53 

Nesting behavior 54 

Nesting period 54 

Nest site and materials : ■_ 55 

Egg laying and clutch size 60 

Cowbird parasitism 62 

Incubation 62 

Care of nestlings 63 

Care of fledglings 64 

Voice 64 

Song 64 

Whisper song 65 

Flight song ^ 66 

Incomplete song 66 

Singing behavior 66 

Seasonal song cycle 68 

Daily pattern 69 

Rate of singing 69 

Cadence of delivery 71 

Comparison with associates 72 

Alarm or call note 72 

Feeding Behavior and Food 74 

Feeding behavior 74 

Bill wiping 75 

Food , 75 

Miscellaneous Notes on Behavior 77 

Ground locomotion 77 

Preening 77 

Head scratching 77 

Tail spreading 78 

Factors Affecting the Population 79 

Summary 81 

Literature Cited 84 

ILLUSTRATIONS 

Frontispiece, Pair of Swainson's Warblers at nest near Jackson- 
ville, Fla. vi 

Figure 

1. The Reverend John Bachman 5 

2. Audubon's painting of Bachman's type specimen 6 

3. Type locality of the Swainson's Warbler 7 

4. Edisto River near Jacksonboro, S.C. 8 

5. John Abbot 9 

6. Abbot's painting of the "Swamp Worm-eater" 10 

7. Brier Creek, Screven County, Ga. 11 



CONTENTS 



Page 



8. Distribution of the Swainson's Warbler 14 

9. Canebrake along edge of Ocmulgee River near Macon, Ga. 27 

10. Canebrake habitat in Ocmulgee River floodplain forest near 

Macon, Ga. 28 

11. Canebrake habitat in Ocmulgee River floodplain forest near 

Macon, Ga. 29 

12. Canebrake habitat in Ocmulgee River floodplain forest near 

Macon. Ga. 30 

13. Typical canebrake breeding territory occupied by a male 

Swainson's Warbler near Macon, Ga. 31 

14. Mixed swamp hardwood habitat in the Dismal Swamp in 

southeastern Virginia 34 

15. Part of scrub palmetto territory of a male Swainson's 

Warbler in Monkey John Swamp, S.C. 35 

16. Rhododendron-hemlock association mountain habitat of the 

Swainson's Warbler along Collison Creek, Nicholas 
County, W. Va. 37 

17. Mountain breeding habitat, Collison Creek, Nicholas 

County, W. Va. 38 

18. Mature mountain cove hardwood habitat of the Swainson's 

Warbler near Charleston, W. Va. 39 

19. Umbrella magnolia, prominent understory tree in habitat 

of the Swainson's Warbler near Charleston, W. Va. 40 

20. Overlapping territories in the Dismal Swamp occupied by 

the same male Swainson's Warbler for 3 successive years 47 

21. Variation in size of male Swainson's Warbler territory 

during breeding season 49 

22. Display of male Swainson's Warbler during boundary dis- 

pute with a neighboring male 51 

23. Swainson's Warbler incubating during flood stage in 

Ocmulgee River floodplain forest canebrake near Macon, 
Ga. 56 

24. Swainson's Warbler nest in greenbrier vine, 2 feet above 

the ground, Dismal Swamp in Virginia 57 

25. Nest of the Swainson's Warbler compared with nest of the 

Cardinal i 58 

26. Nest and eggs of the Swainson's Warbler in cane 61 

Photographs are by the author unless otherwise credited. 




A pair of Swainson's Warblers at their nest near Jacksonville, Fla. 
(Photograph by Samuel A. Grimes). 



VI 



Introduction 

The Swainson's Warbler (Limnothlypis swainsonii) is one of 
the least known of songbirds in the southern United States and 
one that is widely sought by bird enthusiasts. It is unusually 
appealing to the student of birds because it is hard to find, be- 
cause its forbidding habitat is challenging, and because it is as- 
sociated with the Audubon-Bachman period of North American 
ornithology. 

The difficulty of becoming well acquainted with the Swainson's 
Warbler has been noted by a number of field ornithologists. In the 
Alabama River bottoms, Arthur H. Howell of the U.S. Biological 
Survey reported (1928, p. 284-285) it as confined to the deep 
swamps and riverbottom woods where canebrakes occur, and re- 
marked that its secretive habits conceal it from all but the most 
persistent observers. In the big swamps above Mobile in May 
1911, July 1913, and May 1914 he heard at least nine of these 
warblers, but because of the impenetrable vegetation was unable 
to collect any. 

Maurice G. Brooks, Professor of Wildlife Management at West 
Virginia University, and his coworker W. C. Legg (Brooks and 
Legg, 1942, p. 81) found this elusive warbler extremely difficult 
to observe in the dense shadows of the "rhododendron hells" of 
the Alleghenies : 

With their neutral brown coloration, their rapid movements, and their ap- 
parent liking for the centers of the thickets, they seemed to blend imper- 
ceptibly into their surroundings. 

While the remarks of Sprunt and Chamberlain (1949, p. 435) 
are generally true — that "Swainson's Warbler remains today one 
of the few land birds really difficult to find and study" — there are 
times when it can be observed at closer range than almost any 
other songbird. It is not a very suspicious bird. It seems hard to 
find chiefly because of the character of its habitat. 

The bird student seeking this species in a briery-viny entangle- 
ment or canebrake disrupts the peaceful atmosphere of the bird's 
home, naturally frightening it. Or perhaps it is the never-ending 
wall of nearly impenetrable vegetation between the observer and 
the bird that discourages one. But in some habitats, when the 



2 NORTH AMERICAN FAUNA 69 

birds are on breeding territories, and especially during the court- 
ship and preincubation periods when the pair are traveling to- 
gether, they can often be approached to within 5 feet and kept under 
observation at close range for many minutes. Several times during 
its preincubation period, one paired bird fed within 2 feet of my 
eyes as I lay prone on the ground. I found canebrakes to be the 
best habitat for sustained observations : the visual conditions are 
generally uniform, and the birds tend to stay away from the 
densest part of the canebrake. 

Although the Swainson's Warbler is not as abundant as some 
of the other southern warblers, in 1968 I knew of at least two 
areas in which I could find 50 individuals in a single day. One of 
these was the Great Dismal Swamp in southeastern Virginia ; the 
other was the Ocmulgee River floodplain forest, 3 to 5 miles south- 
east of Macon, Ga., where I first became acquainted with the 
Swainson's Warbler (Meanley, 1945, p. 395-401). When stationed 
at Camp Wheeler near Macon, 1944-46, I began making observa- 
tions in the extensive riverbottom canebrakes, and I returned to 
this area for further study in 1963 and each spring thereafter 
through 1968. During these 24 years the habitat and number of 
individuals remained virtually unchanged. 

When living at Alexandria, La., in 1956 and 1957, I made ob- 
servations in Bayou Boeuf Swamp, at the edge of that central 
Louisiana city. In Arkansas in 1967 I obtained information on 
territorial and nesting behavior in the batture (land between the 
levee and the river), between the mouth of Bayou Meto and 
Pendleton Ferry, along the Arkansas River. Mountain habitats 
near the City of Charleston and in Nicholas County, W. Va., were 
visited during the spring of 1965 and 1966. In 1966 I began ob- 
servations in the Great Dismal Swamp, a few miles south of 
Norfolk, Va. This continues to be my main study area. 

METHODS 

Habitats in breeding territories were analyzed in several ways. 
Plant species composition was determined by sampling 1/4-acre 
plots. In canebrake and scrub palmetto (Sabal minor) habitats, 
the density and number of stems were determined by sampling 
10-foot-square quadrats. 

The light-shading effect of the combined canopy, lower tree, 
and shrub strata was determined in 14,-acre plots of several 
tracts. A 2-foot-diameter hoop divided into eight equal sections 
was held directly overhead, and 20 random readings were made, 
sighting upward. Readings were taken between 11:30 a.m. and 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 3 

12:30 p.m. on sunny, windless days. To measure the light in- 
tensity, I placed a mirror on the ground in the exact spot where a 
Swainson's Warbler had been feeding less than 1 minute before, 
held an exposure meter 1 foot above the mirror with the photo- 
electric cell upward, and took a reading. 

Territory-mapping and transect methods were used in making 
censuses. Dimensions of territories were determined by spot- 
mapping males on maps marked off into transects or grids. Stud- 
ies of territorial behavior were facilitated by color-marking birds 
of both sexes with celluloid or metal leg bands. Birds were cap- 
tured with mist nets for marking. 

Birds taken on the breeding and wintering grounds were 
weighed shortly after capture ; birds taken during migration were 
weighed after being held in a freezer for various periods of time. 

Measurements are from files in the U.S. National Museum. 
Time is given as Eastern Standard Time unless otherwise indi- 
cated. Bird names used in the text are from the A.O.U. Check-list 
of North American Birds (1957) ; plant names are from Fernald 
(1950) and Radford, Ahles, and Bell (1964) ; and insect names 
are from Lutz (1935). 

ACKNOWLEDGEMENTS 

I am grateful to many persons for their contributions to this 
project. Anna Gilkeson Meanley, my wife, worked with me on 
several occasions in the Ocmulgee riverbottom canebrakes and in 
the Great Dismal Swamp. Linda Hail, Lucille F. Stickel, Nancy 
C. Coon, Paul A. Stewart, and Van T. Harris reviewed the manu- 
script. Samuel A. Grimes gave me a copy of his superb photograph 
of a pair of Swainson's Warblers at their nest, and Frederick C. 
Schmid made several excellent photographs for me. Oliver H. 
Hewitt of Cornell University presented me with a photograph of 
John Abbott, and E. Milby Burton of the Charleston Museum gave 
me permission to use a photograph of the Reverend John Bach- 
man. The Fogg Art Museum of Harvard University and the 
Harvard College Library made available a copy of John Abbot's 
illustration of the Swainson's Warbler. H. L. Stoddard, Sr., and 
Robert A. Norris of the Tall Timbers Research Station, Talla- 
hassee, Fla., gave me specimens that struck the TV tower at the 
station. Eugene P. Odum and William Dopson of the University 
of Georgia and James B. Cope of Earlham College gave me data 
from specimens in their collections. J. Fred Denton of Augusta, 
Ga., and M. G. Vaiden of Rosedale, Miss., provided me with im- 
portant data from their studies. John W. Aldrich, Gorman M. 



4 NORTH AMERICAN FAUNA 69 

Bond, and Allen J. Duvall of the U.S. Fish and Wildlife Service 
helped with taxonomic problems and other matters. I also wish 
to thank Olin Sewall Pettingill, editor of the Living Bird, and 
George A. Hall, editor of the Wilson Bulletin, for permitting me 
to quote extensively from papers of mine appearing in those 
journals. 



History 

The Swainson's Warbler was described by Audubon from speci- 
mens collected by John Bachman (fig. 1) on the banks of the 
Edisto River in South Carolina in 1832 or 1833. Audubon named 




Figure 1. — The Reverend John Bachman. He collected the type specimen of 
the Swainson's Warbler along the banks of the Edisto River in South 
Carolina in 1832 or 1833. Photograph courtesy Charleston (S.C.) Museum. 



NORTH AMERICAN FAUNA 69 







Figure. 2. — Audubon's painting of the Swainson's Warbler, from Bachman's 

type specimen. 

the new bird for his friend the English ornithologist William 
Swainson, giving it the scientific name Sylvia Swainsonii. 1 Audu- 
bon's painting of the new warbler (fig. 2) appeared in his Birds 
of America (1834a, plate 198). The description appeared in his 



1 The present generic name, Limnothlypis, meaning marsh finch, is credited to 
Stone (1914, p. 26). 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 




ston 



Savannah 



Figure 3. — The arrow-designated circle in South Carolina marks Bachman's 
type locality; that in Georgia marks the approximate locality where Abbot 
collected specimens some 25 years before Bachman. 

Ornithological Biography (Audubon, 1834b, p. 564-565). The 
type specimen was given to the U.S. National Museum by Spencer 
F. Baird, one-time Secretary of the Smithsonian Institution, who 
acquired it from Audubon. 

The discovery of this new species by Bachman, some 25 miles 
south of Charleston, is described as follows (in Audubon 1834b, 
p. 564) : 

I was first attracted by the novelty of its notes, four or five in number, 
repeated at intervals of five or six minutes apart. These notes were loud, 
clear, and more like a whistle than a song. They resembled the sounds of 
some extraordinary ventriloquist in such a degree, that I supposed the bird 
much farther from me than it really was; for after some trouble caused by 
these fictitious notes, I perceived it near me and soon shot it. 

Bachman collected five specimens in the spring of 1832 or 1833. 
The type locality apparently is in the vicinity of Jacksonboro and 
Parker's Ferry Landing, S.C. (figs. 3 and 4). Audubon reported 



NORTH AMERICAN FAUNA 69 





Figure 4. — The Edisto River near Jacksonboro in South Carolina, where 
Bachman collected the type specimen of the Swainson's Warbler. 

that the type specimen was collected in 1832, the year that he was 
on an expedition to Labrador. However, Arthur T. Wayne (1906, 
p. 227), Charleston ornithologist of the late 1800's and early 
1900's, pointed out that since Audubon was in Labrador in 1833 
and not 1832 the type specimen must have been collected in 1833. 
While John Bachman gets the credit for the discovery of the 
Swainson's Warbler, John Abbot (fig. 5), a Georgia naturalist, 
apparently collected a specimen some 25 years earlier but made no 
public record of the event. However, he made an identifiable 
portrait of the bird (fig. 6). Many of Abbot's Georgia bird paint- 
ings were deposited in the British Museum and the Boston Society 
of Natural History. Those, including the Swainson's Warbler, 
deposited in the latter place now repose in the Fogg Art Museum, 
Harvard University. Walter Faxon (1896, p. 207), one of the 
first persons to study Abbot's paintings, made the following re- 
marks about the painting of the Swainson's Warbler : 

On looking through the Abbot bird-portraits several arrest the eye from 
their historic interest. Plate 68 is a good representation of Swainson's- War- 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 9 

bier, drawn at least a quarter of a century before this species was described 
and named by Audubon. On the reverse of the plate is the following auto- 
graph note by Abbot: L. 6. May 8. Swamp. — Swamp Worm-eater. 




Figure 5. — John Abbot (self portrait), Georgia naturalist who collected a 
specimen of the Swainson's Warbler about 25 years earlier than Bach- 
man, but did not report it. His painting of the bird was discovered many 
years later. Photograph courtesy Oliver H. Hewitt, Cornell University. 



During his first years in Georgia after the Revolutionary War,. 
Abbot lived in the town of Jacksonboro in Screven County. Jack- 
sonboro, no longer in existence, was located in the Savannah River 
valley near Sylvania. Abbot did much of his collecting in a swamp, 
along Brier Creek (fig. 7), a tributary of the Savannah. 



10 



NORTH AMERICAN FAUNA 69 




a < i 






Figure 6. — Photograph of John Abbot's painting of the Swainson's Warbler, 
which he called the "Swamp Worm-eater." Illustration courtesy Fogg Art 
Museum, Harvard University, and the Harvard College Library. 



After Bachman collected his historic five specimens in 1832 
or 1833, the Swainson's Warbler was almost a lost species for the 
next 50 years. According to William Brewster (1885a, p. 66). 
only eight or nine specimens were collected during that period. 
Then in 1884, Brewster and Arthur T. Wayne made significant 
collections and studies in the vicinity of Charleston, S.C. (Brew- 
ster, 1885a). Wayne reported the first nest and eggs known to 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 



11 



science (Brewster 1885b, p. 468), near Charleston on June 6, 
1885. Troup D. Perry (1886, p. 188) of Savannah, Ga., found a 
nest 22 days earlier (May 16) but did not report his discovery 
as soon as did Wayne. 

Since the Swainson's Warbler was thought to be restricted to 
the Coastal Plain, ornithologists were surprised to learn by the 
1930's that this warbler was a locally common breeding bird to 
an elevation of about 3,000 feet in the Southern Appalachians. 
Before the 1930's there had been several records from the Pied- 
mont suggesting the possibility of an up-country population. L. M. 
Loomis (1887, p. 347-348) found the bird at Chester, S.C., 150 
miles from the coast, and W. H. LaPrade, Jr., (1922, p. 88-89) 
found a nest with eggs at Atlanta, Ga., 1,050 feet above sea level 
in the foothills of the Appalachians. 





Figure 7.— Approximate location on Brier Creek, Screven County, Ga., where 
Abbot collected the "Swamp Worm-eater." 



12 NORTH AMERICAN FAUNA 69 

The first record of this species in the Appalachians is apparently 
based on a specimen collected on June 14, 1924, by P. C. Bibbee 
(see Brooks and Legg, 1942, p. 76) in West Virginia. The bird 
was taken at Buzzard's Rocks, Monongalia County, in what 
Brooks and Legg describe as "a rugged region of hemlock-and- 
rhododendron-clad mountains only a few miles from the Pennsyl- 
vania border." 

Additional early records from the Appalachians are those of 
T. D. Burleigh, who collected three specimens near Asheville, N.C., 
on September 17, 1930, August 31, 1931, and September 14, 1932, 
(in U.S. National Museum collection) and those of E. A. Williams 
(1935, p. 458-459) who sighted several birds near Tryon, N.C., 
on May 8, 1934. The Swainson's Warbler was established as a 
breeding bird of the Appalachians in the summer of 1932 when 
F. M. Jones discovered several nests in southwestern Virginia 
near Bristol (Murray, 1939, p. 9). 



Distribution 

BREEDING RANGE 

The Swainson's Warbler spends nearly 6 months of the year in 
the United States (fig. 8). During this period the bird is primarily 
associated with the river floodplain forests and swamps of the 
South Atlantic and Gulf Coastal Plains, and with the rich moist 
woods of the Mixed Mesophytic forest (see Braun, 1950, p. 39-49) 
of the Southern Appalachians. The mountain habitats are in the 
hemlock-rhododendron (Tsuga canadensis-Rhododendron maxi- 
mum) association and the cove hardwoods forest. Apparently the 
Piedmont Province is generally unsuitable for occupation by this 
species. While there are scattered records of its occurrence in the 
Piedmont Province during the breeding season, there appear to be 
no breeding concentrations in this in-between area. The swamps 
and floodplain forests of the Coastal Plain, and sections of the 
Mixed Mesophytic forest where this species occurs in the moun- 
tains, are more humid than most of the forests of the Piedmont. 

During the summer the climatic features of the two major 
physiographic regions occupied by the Swainson's Warbler are 
somewhat similar. Blair (1942, p. 130, 132) has classified the 
climate of the South Atlantic and Gulf Coastal Plains as Humid 
Subtropical type, and the climate of the Southern Appalachians 
as Humid Continental type (warm long summer subtype). The 
Humid Subtropical climatic type has a moderate-to-heavy rainfall 
at all seasons, usually with a maximum in summer ; 9 to 12 months 
with mean temperature above 50° F. ; and a growing season of 
220 days or more. The Humid Continental type (warm long sum- 
mer subtype) has a rainfall between 20 and 40 inches with a 
summer maximum ; 6 to 9 months with mean temperature above 
50° F. ; and a growing season of 140 to 220 days. 

Atlantic Coastal Plain 

Along the Atlantic Coastal Plain the Swainson's Warbler occurs 
from extreme southern Delaware to southeastern Virginia and 
southward and inland as far as the fall line to about Jacksonville 
and the Suwannee River in Florida. 

The northern limit on the Atlantic coast is the Pocomoke River 
Swamp in Sussex County, Del., and Worcester County, Md. The 
Pocomoke Swamp lies about 10 miles inland from the Atlantic 



14 



NORTH AMERICAN FAUNA 69 





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Figure 8. — Distribution of the Swainson's Warbler. Hatched area indicates 
general limits of breeding range; solid black area indicates general limits 
of winter range. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 15 

Ocean and extends from just above the Delaware-Maryland line 
southward nearly to the Virginia boundary. Only a few scattered 
pairs nest in this cypress-gum disjunct swamp. 

The Swainson's Warbler is locally common in the Great Dismal 
Swamp in southeastern Virginia and northeastern North Caro- 
lina, and in certain floodplain forests just below the fall line. In 
many of these river floodplains its distribution coincides with 
that of the giant cane ( Arundinaria gigantea). It was also re- 
ported to be common in the 1960's in the Ocmulgee River flood- 
plain forest, 3 to 5 miles south of Macon, Bibb County, Ga. ; in 
the Savannah River Valley, from Augusta, Richmond County, 
Ga., downstream about 25 miles; and in the Wateree River 
Swamp, northwest Sumter County, S.C. Scattered pairs and sing- 
ing males have been reported from many other areas in the 
Carolinas and Georgia. 

The distributional status of the Swainson's Warbler in the 
lower Coastal Plain of South Carolina and Georgia has apparently 
changed in the last 50 years. In the Living Bird, Fifth Annual, 
(Meanley, 1966, p. 152), I made the following comments regard- 
ing the former abundance of this species in the lower Coastal 
Plain of the Southeast : 

At the close of the 19th century and the beginning of the 20th, Swainson's 
Warblers were apparently more numerous in the lower Coastal Plain than 
they are today. Wayne (1910:149-150) found them to be common breeding 
birds near Charleston, South Carolina, as did Perry (1887:142) near Savan- 
nah, Georgia. During the period of 22 April to 25 September 1884, Wayne 
collected 47 specimens of this species near Charleston. Considering modes of 
travel available to Wayne and the limited area of his operations, his collect- 
ing of so many specimens would seem to indicate a sizable population in the 
area. Perry (1887) reported 24 active nests near Savannah in the spring of 
1887, which likewise suggests that Swainson's Warblers were more abundant 
in the late 19th century than at present. E. S. Dingle of Huger, South 
Carolina, who worked with Wayne and who bridged the gap between Wayne's 
time and the present, informed me in April 1958 that he had noted during 
his lifetime a marked downward trend of the population in the coastal area. 
A. Sprunt, Jr. (in Sprunt and Chamberlain, 1949:435), a protege of Wayne's, 
has seen this warbler only four times in the lower Coastal Plain of South 
Carolina. 

In the lower Savannah River Valley, an area extending 30 miles upriver 
from Savannah, E. O. Mellinger and I found only scattered individuals and 
occasional pairs during the early 1960's — certainly not the numbers and 
concentrations found farther up the valley near Augusta, as reported by 
Murphey (1937:42), Norris (1963:47), and J. F. Denton (pers. commun.). 

Gulf Coastal Plain 

In the Gulf Coastal Plain the Swainson's Warbler occurs from 
north of the Suwannee River in northern Florida, northward and 



16 NORTH AMERICAN FAUNA 69 

westward to southern Alabama, eastern, Mississippi, and the 
lower Mississippi Valley as far as southern Illinois, and westward 
through southern Arkansas and the southeastern corner of Okla- 
homa to at least Brazos County, Tex. 

During the mid-20th century, areas where it was reported as 
locally common were mostly in the lower Mississippi Valley. How- 
ever, the lower Mississippi Valley was the center of the most 
intensive ornithological investigations during the period. It un- 
doubtedly was common also in many areas east of the lower 
Mississippi Valley. 

In northwestern Florida it was formerly reported as a locally 
common breeding bird along the Wacissa River near Waukeenah, 
along the Suwannee River near Old Town (Wayne, 1893, p. 338 ; 
1895, p. 367), and along the Aucilla River (Howell, 1932, p. 386). 
F. M. Weston (1965, p. 105) regarded it as an uncommon summer 
resident at Pensacola. 

In Alabama it is rather widely distributed, with breeding con- 
centrations in the Alabama River bottoms above Mobile and in 
the vicinity of Bear Swamp a few miles west of Montgomery 
(Howell, 1928, p. 284; Imhof, 1962, p. 439). 

In the Louisiana section of the lower Mississippi Valley, G. H. 
Lowery (personal communication, 1962) reported it as commonly 
breeding in the vicinity of Baton Rouge, and I found it locally 
common in 1956-57 in Bayou Boeuf Swamp near Alexandria as 
well as in the Tensas River area a few miles south of Tallulah. 

In the Mississippi River Delta, at Rosedale, Bolivar County, 
Miss., M. G. Vaiden (personal communication, 1968) found nests 
and reported the species as fairly common in the batture along 
the Mississippi River. 

In eastern Arkansas I found it locally common in the lower 
White River bottoms, in the East Moon Lake and Scrubgrass 
Bayou areas, and along the Arkansas River between the mouth 
of Bayou Meto and Pendleton Ferry. Five nests were located 
in the latter locality between 1966 and 1968. 

Apparently the Swainson's Warbler was a breeding bird in the 
late 1800's and early 1900's in the St. Francis River "sunken 
lands" of southeastern Missouri and northeastern Arkansas, 
where it occurred in canebrakes with the Bachman's Warbler 
(Vermivora bachmanii) (Widmann, 1895, p. 115-117) . Since the 
time of Widmann's investigations, much of the swampland in that 
area has been drained and the canebrakes destroyed. 

At Memphis, Tenn., B. B. Coffey, Jr., (1941, p. 30-31) reported 
Swainson's Warblers nesting within the city limits and in at least 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 17 

10 localities in surrounding Shelby County. These warblers occur 
regularly in most of the Coastal Plain riverbottoms of western 
Tennessee and in the Reelfoot Lake area. Mengel (1965, p. 389) 
reported the species as "fairly common locally in lowland forests 
of extreme western Kentucky (Fulton, Hickman, and Ballard 
Counties), rare and local in swamp forests of the Pennyroyal and 
Western Highlands." 

The Gulf Coastal Plain extends as far northward as the south- 
ern tip of Illinois, a short distance above the confluence of the 
Ohio and Mississippi Rivers. Records from the Coastal Plain of 
southern Illinois are as follows : Olive Branch, Alexander County, 
May 15 and 20, 1909, and Reevesville, Johnson County, June 
21-22, 1909 (Howell, 1910, p. 216) ; Cairo, Alexander County, 
September 1, 1938, female collected (Ammann, 1939, p. 185-186) ; 
and DuQuoin, Perry County, a few miles north of the Coastal 
Plain, June 7, 1907 (Gross, 1908, p. 225) . 

The breeding range of the Swainson's Warbler west of the 
Mississippi Valley is imperfectly known. It has been found during 
the breeding season as far west as Brazos County, Tex. (Purring- 
ton, 1966, p. 35) ; and in southeastern Oklahoma (McCurtain 
County) just beyond the Coastal Plain (Sutton, 1967, p. 491). 

Southern Appalachians 

The Swainson's Warbler breeds in the mountains in south- 
central West Virginia, perhaps southeastern Ohio, eastern Ken- 
tucky, southwestern Virginia, eastern Tennessee, western North 
and South Carolina, and northern Georgia and Alabama. 

In West Virginia, Swainson's Warblers occur mostly on the 
Allegheny Plateau, west of the main Allegheny ridges. M. G. 
Brooks and W. C. Legg (1942, p. 78) found the species locally 
common near Mt. Lookout, Nicholas County, where elevations 
are between 2,200 feet and 1,300 feet at the Gauley River level. 
The three principal streams along which Swainson's Warblers 
were found are Gauley River; Collison Creek, a tributary of the 
Gauley ; and Anglins Creek, a tributary of Meadow River. 

The Swainson's Warbler breeds commonly in the mountain 
ravines opposite Charleston, W. Va., in the Kanawha River Valley. 
Charleston lies at an elevation of about 600 feet, and the birds 
are found from the city limits upward. Fifty miles west of 
Charleston, in the Ohio River Valley, there are records from 
Huntington, W. Va., (Seeber and Edeburn, 1952) and across the 
river at Chesapeake, Lawrence County, Ohio (Green, 1947, p. 
211). M. G. Brooks (1965, p. 281) states that Swainson's War- 
blers are known from 14 West Virginia counties. 



18 NORTH AMERICAN FAUNA 69 

In the mountains of eastern Kentucky this warbler was first 
noted by G. H. Brieding (1944, p. 6-7) on Black Mountain, 
Harlan County, on July 5 and 6, 1944. R. M. Mengel (1965, p. 
391) collected a specimen on June 26, 1951, near Elkhorn City, on 
the line between Dickinson County, Va., and Pike County, Ky. 
The elevation at this point is about 2,200 feet. 

Farther south along the Appalachian chain in the Holston 
Mountains of southwestern Virginia and northeastern Tennessee, 
nesting has been recorded by F. M. Jones near Bristol, Washing- 
ton County, Va. (Murray, 1939, p. 9). Three miles northeast of 
Shady Valley, Johnson County, Tenn., W. M. Perrygo and C. 
Lingebach collected an adult male at an elevation of 3,000 feet on 
June 8, 1937, and observed two others at 2,600 feet elevation 5 
miles north of Shady Valley near Beaverdam Creek (specimen in 
U.S. National Museum) . 

In western North Carolina, T. D. Burleigh collected three 
specimens near Asheville, in the Pisgah National Forest, one 
each on September 17, 1930, August 31, 1931, and September 14, 
1932 (specimens in U.S. National Museum). At Tryon, near the 
North Carolina-South Carolina border, E. A. Williams (1935, p. 
458-459) observed a Swainson's Warbler on May 8, 1934, and 
the following year observed a pair from May 9 to 14. 

An important concentration area of this species in the Southern 
Appalachians is where the States of North Carolina, South Caro- 
lina, and Georgia meet. H. M. Stevenson, Jr., (1941, p. 46) re- 
ported Swainson's Warblers from Highlands, Macon County, N.C., 
June 20, 1937, at 3,800 feet elevation, and July 3, 1937, at 3,700 
feet elevation. J. F. Parnell and T. L. Quay (1964, p. 144) re- 
ported Swainson's Warbler "as a rather common summer resi- 
dent" at Toxaway River Gorge, Transylvania County, N.C. In 
that area at an elevation of 1,400 feet Parnell observed an adult 
feeding young. R. H. Peake, Jr., (1965, p. 114) reported finding 
a bird near Cashiers, Jackson County, N.C, April 22, 1965. 

In western South Carolina an adult male was taken by W. M. 
Perrygo at Walhalla, Oconee County, June 25, 1940. Also in 
Oconee County, J. B. Shuler (1962, p. 75-76) noted a singing 
male in the Sumter National Forest, May 19 and 30, 1962. 

The first record in the mountains of Georgia was obtained June 
3, 1948, by C. Neal and J. F. Denton (Denton, 1948, p. 24-25), at 
an elevation of 1,700 feet on Tray Mountain near Robertstown, 
White County. In the same locality, Denton and Neal (1951, p. 
27-28) saw three males on May 8, 1949, and four males on May 
9, 1950. At Clayton, Rabun County, Ga., E. O. Mellinger (personal 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 19 

communication) observed two pairs almost daily during April, 
May, and June 1968. 

In Alabama, T. A. Imhof (1962, p. 439) recorded this species 
in the northeastern corner of the State (Long Island Gulf, Jack- 
son County), at 1,150 feet, June 7, 1957. 

Ozark Mountains 

There are records of birds in two locations in the Arkansas 
Ozarks. D. A. and F. C. James and S. Hilty (1966, p. 577) 
recorded three territorial males 12 miles southeast of Yellville, 
Marion County, Ark., June 25, 1966. At Fayetteville, Washington 
County, in the northwestern corner of the State, the Jameses 
(1966, p. 518) observed a male on territory daily, May 4 to 31, 
1966. 

Westward beyond the Ozarks, the breeding range extends into 
the Prairie Plains physiographic region of northeastern Okla- 
homa. Nice (1931, p. 155) reported that A. J. Kirn located several 
nests along the Little Caney River near Copan, Washington 
County, in June 1914 and June 1917. This locality is only about 
10 miles from the Kansas border. A more recent occurrence in 
the same county was reported at Bartlesville, April 23, by S. Veal 
(Williams, 1966, p. 524). 

Piedmont province 

The following are records made during the breeding season. 
Records from the Piedmont province before May and after July 
may represent either birds on their breeding grounds or migrants. 

Virginia. — Charlottesville, in the upper Piedmont, in the foot- 
hills of the Blue Ridge Mountains: Summer 1913 (Ferneyhough, 
1914, p. 291), and spring 1961 through 1964, by R. S. Merkel 
(Scott and Cutler, 1964, p. 442). 

South Carolina. — Greenwood County, near the Savannah River 
Valley, approximately 40 miles above the fall line: July 3, 1924, 
nest (F. W. Hahn in Sprunt and Chamberlain, 1949, p. 436). 

Georgia. — Atlanta, in the foothills at an elevation of about 
1,200 feet: May 27, 1920, and May 30, 1922, nests (LaPrade, 
1922, p. 88-89). Athens: May 20, 1921 (Burleigh, 1938, p. 24). 

Kentucky.— Bullitt County: June 27, 1937 (Carpenter, 1937, 
p. 32). 

Extralimital records (United States) 

Records of occurrence beyond the limits of the normal breeding 
range are as follows: Kearney, Neb., April 9, 1905, by C. A. Black 
(Worthen, 1906, p. 227) ; Holly, Prowers County, Colo., May 12, 
1913 (Lincoln, 1918, p. 236) ; Prospect Park, New York City, 



20 NORTH AMERICAN FAUNA 69 

May 5, 1950, by Carleton and Helmuth (Bull, 1964, p. 362) ; Mt. 
Carmel, Wabash County, 111., April 1878 (Ridgway, 1878, p. 163) ; 
Lake Quivira, Johnson County, Kans., May 11, 1957 (Hardy, 
1957, p. 10) ; and Linwood, N.J., May 23, 1968 (Savell, 1968, p. 
159). 

WINTER RANGE 

The main wintering grounds are the Caribbean archipelago in 
the general area of latitude 20° N., including Jamaica and Cuba, 
and the Yucatan Peninsula south to British Honduras (fig. 8). 2 

Cuba 

Oriente Province. — Guantanamo: January 18, 1914, male col- 
lected (Ramsden, 1914, p. 253). 

Las Villas Province. — Cienf uegos : December 23, 1948, through 
January 3, 1949, several specimens collected (Eaton, 1953, p. 
169). 

La Habana Province. — Havana: September 25, year ?, one 
specimen collected, and April 14, 1922, one specimen collected, 
both possibly migrants (from the distribution files of the Migra- 
tory Bird Populations Station of the Bureau of Sport Fisheries 
and Wildlife, at Laurel, Md.). 

Jamaica 

St. Thomas Parish. — Kingston: December 31, 1946, and Feb- 
ruary 5 and 7, 1947, 3 females collected; December 3, 1946, 
through February 7, 1947, 9 birds observed (Tordoff, 1952, p. 
321). Port Royal Mountain: February 18, 1879, specimen col- 
lected by E. Newton (Merriam, 1885, p. 377). 

St. Andrew Parish. — Hope : February 1879, specimen collected 
by E. Newton (Merriam, 1885, p. 377). Hermitage: April 8, 1879, 
specimen collected by E. Newton (Merriam, 1885, p. 377). Mt. 
Elizabeth: October 1 and 7, 1879, December 21, 1881, and March 
16, 1882, specimens collected by E. Newton (Merriam 1885, p. 
377). 

Swan Islands 

A specimen was collected on March 1, 1912 (Peters, 1913, p. 
378). The Swan Islands are in the Caribbean Sea, between the 
Yucatan Peninsula and Jamaica, near latitude 18° N. and longi- 
tude 84° W. 



2 There are several records for the Bahama Islands that probably represent migrants, 
and they are treated as such here. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 21 

Mexico 

Quintana Roo. — Santa Lucia: January 24, 1912, specimen col- 
lected (Peters, 1913, p. 378). Chetumal : February 12, 1949, speci- 
men collected (Paynter, 1955, p. 242). Cozumel, Cozumel Island: 
December 27, 1961, specimen collected by L. C. Binford (Louisi- 
ana State University collection). 

Campeche. — Pacaytain : January 15, 1940, specimen collected 
(Traylor, 1941, p. 219). 

Veracruz. — Veracruz: winter of 1887-88 (distribution files, 
Migratory Bird Populations Station). 

British Honduras 

February 20, 1956, specimen collected by S. M. Russell (Louisi- 
ana State University collection) in the Orange Walk District. 



Migration 

SPRING 

Swainson's Warblers apparently follow the most direct routes 
in migrating from wintering to breeding grounds. From West 
Indian wintering grounds they apparently reach the United 
States by island-hopping to southern Florida. Birds moving north- 
ward from eastern Cuba and Jamaica may touch some of the 
Bahama islands and cays enroute: there are March and April 
records from Bimini, Andros Island, and Cay Lobos. 

The northern coast of Yucatan is a natural departure point for 
trans-Gulf flight to the Gulf Coast of the United States. Studies 
by G. H. Lowery (1945, p. 92-121; 1946, p. 175-211) and H. M. 
Stevenson (1957, p. 39-77) and observations by several other 
ornithologists lend credence to a trans-Gulf movement of Swain- 
son's Warblers from the northern coast of Yucatan and the shore 
of the Bay of Campeche. The distribution of casualties at the 
base of the Tall Timbers TV tower near Tallahassee, Fla., 50 
miles from the Gulf, indicates that the spring flight through that 
region is mainly in a southwest-to-northeast direction (Stoddard 
and Norris, 1967, p. 11, 15). Stoddard and Norris believe that this 
is mainly a trans-Gulf flight, with a minor segment of the flight 
skirting the Gulf. The lesser migration, which they refer to as the 
"Florida Peninsula-West Indian Flight" comes through mainly 
on easterly, southeasterly, and southerly winds. 

It is probable that some of the Swainson's Warblers that winter 
in eastern Mexico migrate around the Gulf, moving northward 
along the eastern coasts of Mexico and Texas. The numerous 
spring records from coastal Texas could represent both trans-Gulf 
and circum-Gulf migrants. 

Exceptionally early arrivals reach Florida by the middle of or 
the third week of March. There are records by J. Johnson and 
D. R. Paulson for March 16 offshore near Eau Gallie and for 
March 19 at Goulds, south of Miami (Stevenson, 1960, p. 304), 
and Bush Key pond, Dry Tortugas, March 17, 1964 (Robertson 
and Mason, 1965, p. 136). The first wave of migrants reaches 
northern Florida during the last week in March. At Tallahassee, 
during the period 1956 to 1966, 14 of 83 birds striking the Tall 

22 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 23 

Timbers TV tower arrived in the last week of March (Stoddard 
and Norris, 1967, p. 71). The earliest arrival date at Tallahassee 
was March 21. 

Earliest arrivals at other localities are as follows: New Orleans, 
La., one on March 30 and four on April 1 (Kopman, 1905, p. 292; 
and 1915, p. 186) ; Savannah, Ga., March 25 (Burleigh, 1958, p. 
495) ; Macon, Ga., March 31 (B. Meanley, MS.) ; and noted by 
K. McCracken and E. Payne, Corpus Christi, Tex., March 28 
(Webster, 1966, p. 531). 

Average dates of first arrivals are : Baton Rouge, La., April 2 
(Lowery, 1945, p. 107) ; Alexandria, La., April 3 (B. Meanley, 
MS.) ; Macon, Ga., April 3 (B. Meanley, MS.) ; Augusta, Ga., 
April 3 (J. F. Denton, Jr., personal communication) ; Suffolk, Va. 
(Dismal Swamp), April 15 (B. Meanley, MS.); Clayton, Ga. 
(mountains), April 17 (E. O. Mellinger, personal communica- 
tion) ; Charleston, W. Va., April 15-17 (Sims and DeGarmo, 1948, 
p. 3) ; and Maryland-Delaware boundary (Pocomoke Swamp), 
April 21 (Meanley, 1950, p. 94). 

The main flights at Tallahassee, Fla., for the period 1956 to 
1966 were during the first and second weeks in April, when 50 
of 83 birds that struck the Tall Timbers TV tower (Stoddard 
and Norris, 1967, p. 71) were reported to be this species. At 
Macon, Ga., from 1963 to 1968, the main flights were in the 
second week of April (B. Meanley, MS.). At Charleston, W. Va., 
the main flight was April 19 (Sims and DeGarmo, 1948, p. 3). At 
the Dismal Swamp in southeastern Virginia, the main flight was 
during the third week in April (B. Meanley, MS.). 

FALL 

During 3 years at Macon, Ga., and at Gillett, Ark., I made 
weekly observations from the time the local population arrived in 
the spring until it departed in the fall,. and I found that most of 
the breeding population remained until about the middle of Sep- 
tember. A. T. Wayne (1910, p. 150) reported that at Charleston, 
S.C., "The song period lasts from their arrival until September 
15." E. Sims and W. R. DeGarmo (1948, p. 3) stated that at 
Charleston, W. Va., "singing males were heard briefly in early 
mornings as late as September 15." 

Apparently the bulk of the birds migrate through the Deep 
South between the middle of September and the middle of Octo- 
ber. At the Tall Timbers TV tower at Tallahassee, Fla., Stoddard 
and Norris (1967, p. 71) reported, 58 of 60 fall strikes of this 
species occurred between September 11 and October 10. 

The earliest migrants reach the middle Gulf Coast by early 



24 NORTH AMERICAN FAUNA 69 

August and the Florida Keys by mid- August and early September. 
Migrants were reported at Gulfport, Miss., on August 8 and 19, 
and at Deer Island, Miss., on August 26 (Burleigh, 1945, p. 110) ; 
at Sombrero Key, Fla., on August 17 (Howell, 1932, p. 386) ; and 
at Dry Tortugas, Fla., by September 2-9 (Sprunt, 1951, p. 224). 

Late records of departure are : Knoxville, Tenn., October 7 and 
8 (Howell and Tanner, 1951, p. 62) ; Tybee Island, near Savannah, 
Ga., October 18 (distribution files, Migratory Bird Populations 
Station) ; Tallahassee, Fla., October 14 (Stoddard and Norris, 
1967, p. 71) ; and Sombrero Key, Fla., November 8, 10, and 13 
(Howell, 1932, p. 386). 

The migration route to the wintering grounds is apparently 
the reverse of that to the breeding grounds. The distribution of 
casualties at the base of the Tall Timbers TV tower indicates 
that the heaviest flight is from northeast to southwest, the direc- 
tion of trans-Gulf migration. Some birds that migrate through 
southern Florida also pass through the Tallahassee area in the fall 
(Stoddard and Norris, 1967, p. 71). 

The coast of Georgia and the eastern coast of Florida are also 
a southward migration route, as evidenced by the following rec- 
ords : Tybee Island, Ga., September 23 and 24 and October 2 and 

18 (Burleigh, 1958, p. 496) ; Jacksonville, Fla., October 5 and 7, 

19 birds picked up at TV towers (Cunningham, 1965, p. 29) ; St. 
Augustine, Fla., September 14 (distribution files, Migratory Bird 
Populations Station); Miami, Fla., October 2 (L. A. Stimson, 
distribution files, Migratory Bird Populations Station) ; and 
Loxahatchee National Wildlife Refuge, Fla., October 6 (P. W. 
Sykes, Jr., personal communication). 

Southward movement along the Gulf Coast in Texas and north- 
ern Mexico would be expected, but records are fewer for the fall 
than for the spring: Rockport, Tex., October 20 (C. H. Hagar, 
distribution files, Migratory Bird Populations Station) ; Kemak, 
Tex., September 27 (J. S. Heiser, distribution files, Migratory 
Bird Populations Station) ; and Matamoros, Tamaulipas, Mexico, 
just over the Texas border from Brownsville, August 29 (Phillips, 
1911, p. 84). 

Early arrival records in the West Indies are: Havana, Cuba, 
September 25 (Bent, 1953, p. 38) ; and Mt. Elizabeth, Jamaica, 
October 1 and 7 (Merriam, 1885, p. 377). 



Ecological Relations 

The optimum habitat of the Swainson's Warbler is a rich, damp 
(but not wet) woods with deep shade and moderately dense under- 
growth. This combination occurs in the physiographic areas in 
which this species is nearly always found — namely, the floodplain 
and swamp forests of the Atlantic and Gulf Coastal Plains and 
certain plant associations of the mixed mesophytic forest of the 
Southern Appalachians. When in swamps, the Swainson's War- 
bler frequents those parts that usually are not inundated, but 
occasionally on the Coastal Plain it may be observed foraging 
along the wet margin of a swamp or in low wet spots that have 
been left from receding floodwaters in floodplain forests. In such 
situations, its foraging behavior on the ground may resemble that 
of the Louisiana Waterthrush (Seiurus motacilla) . Where inunda- 
tion is present in a floodplain forest, it is usually the result of late 
spring floods or heavy rains, after the birds have selected a breed- 
ing territory in a dry section of woods. 

Whether on the Coastal Plain or in the mountains, this species 
is usually near some major drainage system. The river valleys 
provide moist conditions on the breeding grounds, as well as 
"highways" for migration. 

In Coastal Plain forests, where most of my experience has been, 
it is my observation that the Swainson's Warbler, more than its 
closest avian associates, is restricted to the shadier part of the 
forest. Species such as the Carolina Wren (Thryothorus ludo- 
vicianus), the White-eyed Vireo (Vireo griseus), the Prothonotary 
Warbler (Protonotaria citrea), the Hooded Warbler (Wilsonia 
citrina), the Kentucky Warbler (Oporomis formosus), the Cardi- 
nal (Richmondena cardinalis), and the Rufous-sided Towhee 
(Pipilo erythrophthalmus) spend only a part of their time in parts 
of the forest as shady as those frequented most of the time by the 
Swainson's Warbler. The deep shade of the Swainson's Warbler 
environment is the result of dense upper canopy, layer of lower 
trees, and shrub strata. Herbaceous ground cover is absent in 
most of the warbler's habitats, and where it occurs it is usually 
of little consequence as a shade producer. 

The Swainson's Warbler lives mostly in the shrub stratum and 

25 



26 NORTH AMERICAN FAUNA 69 

on the ground. In many habitats, the shrub stratum, or under- 
growth, is composed mainly of a single species such as giant cane 
in the floodplain forest, sweet pepperbush (Clethra alnifolia) in 
the swamp forest, scrub palmetto in the bottomland forest, and 
rhododendron (Rhododendron maximum) in the mixed mesophytic 
forest. The structure of the undergrowth may be remarkably uni- 
form, as in some canebrakes, palmetto thickets, and sweet pepper- 
bush stands. 

GOASTAL PLAIN 

In the Coastal Plain Province, river floodplain forests and 
swamps are the principal physiographic types in which the Swain- 
son's Warbler lives during the breeding season, or summer half 
of the year. Since the terms swamp, riverbottom, hardwood 
bottom, and floodplain forest are often used synonymously, an 
explanation of these terms seems appropriate. The lowland forest 
bordering a southern river is generally known to the forester or 
plant geographer as a riverbottom or bottomland. It is usually a 
complex of several forest communities, including swamps, flood- 
plain forests (also known as hardwood bottoms), and riverfront 
hardwoods. Most swamps are permanently flooded except during 
droughts; they thus differ from floodplain forests which are 
periodically flooded, usually in late winter or spring. There are 
several types of swamps. Those in riverbottoms are known as 
river or alluvial swamps; they are found in the lowest part of 
the bottomland, either bordering the river or between the flood- 
plain forest and adjacent uplands. Swamps found away from 
riverbottoms are known as nonalluvial or inland swamps; good 
examples are the Great Dismal and Okefenokee Swamps. 

Recognized as subdivisions within the floodplain or bottomland 
forests of the lower Mississippi Valley are the first bottoms, and 
the ridge bottoms (or cane ridges) . In low, poorly drained flats of 
the first bottoms, the Overcup Oak-Bitter Pecan (Quercus lyrata- 
Carya aquatica) type is predominant. The Sweetgum-Water Oak 
(Liquidambar styraciflua-Quercus nigra) type is found in the 
better drained parts of the first bottoms. Sweet Pecan (Carya 
illinoensis), Sweetgum, and Southern Red Oak (Quercus falcata) 
are prominent on the cane ridges. These subdivisions are not as 
distinct or are non-existent in the South Atlantic coastal floodplain 
forests. 

In floodplain and swamp forests, the main plant formations 
selected by the warbler are usually canebrakes (figs. 9-12), scrub 
palmetto, and sweet pepperbush. Greenbrier (Smilax spp.) is 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 27 




Figure 9. — Canebrake along the edge of the Ocmulgee River, about 3 miles 
south of Macon, Bibb County, Ga., 1968. 

often associated with sweet pepperbush where the Swainson's 
Warbler is found. 

The canebrake is the prime and classic habitat of the Swain- 
son's Warbler on the Coastal Plain. This habitat has mostly dis- 
appeared, having been reclaimed for agriculture, or grazed, 
burned, or flooded out of existence. Canebrakes are restricted 
mostly to floodplain forests or hardwood bottoms. In the lower 
Mississippi River Valley they occur on first bottom ridges, which 
are well-drained areas; whereas on the South Atlantic Coastal 
Plain they occur along the river and stream edges in floodplain 
forests where there is little change in elevation from the river to 
the edge of the uplands. Thus, they are subject to partial inunda- 
tion during periods when the bottomlands are flooded. 

Scrub palmetto occurs in floodplain forests and swamps in the 
southern part of the Coastal Plain breeding range of the Swain- 
son's Warbler. Sweet pepperbush is an important plant for the 
Swainson's Warbler in the northern part of its Atlantic Coastal 
Plain breeding range. This was the principal habitat in which I 
found it in the Great Dismal Swamp of southeastern Virginia and 
the Pocomoke Swamp on the Eastern Shore of Maryland. In some 
places, sweet pepperbush stalks have a somewhat canebrakelike 
aspect, the main stems growing fairly straight, with similar 
spacing or density and shade effect. 



28 



NORTH AMERICAN FAUNA 69 







Figure 10. — Canebrake habitat in the Ocmulgee River floodplain forest near 
Macon, Ga. The longest poles are 30 feet in length. The diameter of the 
largest poles is 1M inches. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 



29 




Figure 11. — Canebrake habitat in the Ocmulgee River floodplain forest near 
Macon, Ga. The overstory is mainly ash, hackberry, elm, and ash-leaved 
maple. 



30 



NORTH AMERICAN FAUNA 69 



fjl M^ ' 
















Figure 12. — Canebrake habitat in the Ocmulgee River floodplain forest near 
Macon, Ga. Of 91 territorial males that I observed along the Ocmulgee 
over a period of years, 87 had territories in canebrakes. 



Ocmulgee River jloodplain forest in Georgia 

In this area the Swainson's Warbler is found in the extensive 
canebrakes some 3 to 5 miles southeast of Macon in Bibb County 
in central Georgia (Meanley, 1945). The largest stands I have 
ever seen of the fast-disappearing canebrake habitat occur in this 
area. In 1968, there were still some sections in the Ocmulgee 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 31 




Figure 13. — Typical canebrake breeding territory occupied by a male 
Swainson's Warbler near Macon, Ga., May 1965. 



floodplain forest where canebrakes, nearly uninterrupted, covered 
1-square-mile areas. The cane poles in these stands averaged about 
15 feet in height and three-fourths of an inch in diameter at 
ground level. The largest poles reached 30 feet in height and an 
inch and a half in diameter at base. In the Living Bird, Fifth 
Annual, (Meanley 1966, p. 155) I published notes on the density 
of a tract of cane in a male Swainson's Warbler territory (fig. 13) 
near Macon : 



32 NORTH AMERICAN FAUNA 69 

The number of cane poles in 10 quadrats varied from 18 to 75 per 10-foot- 
square quadrat. There were about 20,000 cane poles per acre in my sample 
area which was virtually devoid of other plants, except for a scattering of 
large trees. 

Of 91 territorial males that I observed in seven nesting seasons 
near Macon, 87 had territories (averaging about 1 acre each) in 
patches of cane growing beneath the floodplain forest canopy. 
The floodplain forest in this area was composed mainly of the 
following trees (in descending order of abundance) : hackberry 
(Celtis occidentalis), boxelder (Acer Negundo), red ash (Frax- 
inus pennsylvanica) , American elm (Ulmus americana), sweet- 
gum, water oak, swamp chestnut oak (Quercus Michauxii) , silver 
maple (Acer saccharinum) , and mulberry (Morus sp.). The 
understory was mostly cane, but in openings included blackberry 
(Rubus sp.), swamp privet (Forestiera acuminata), or saplings 
of the above-mentioned trees. The coverage of the combined strata 
of upper canopy, lower trees, and understory was about 85 per- 
cent. Twelve exposure meter readings, made at feeding sites of 
four Swainson's Warblers, ranged from 100 to 225 footcandles. 

The ground in areas occupied by the warblers is dry except 
during periodic flooding. During three nesting seasons when I 
entered the floodplain forest the water was 6 feet deep in some 
canebrake areas where I usually conducted studies. Sometimes 
these floodwaters recede in less than a week, and the habitat re- 
turns to normal. Such flooding sometimes occurs during the height 
of the nesting season, with a devastating effect on nesting success, 
since the average nest height is about 4 feet, and some nests are 
only a foot and a half from the ground. 

A 7-acre tract of cane about 3.5 miles southeast of Macon had 
three territorial males in 1944, five in 1945, four in 1963, and one 
in 1968. There was gradual reduction in the amount of cane in 
this tract over the 24-year period. In 1968, I counted 19 territorial 
males along a 2-mile transect about 5.5 miles southeast of Macon 
in an area known as Bond Swamp. 

The following notes that I made on breeding bird associates 
appeared in the Living Bird, Fifth Annual, (Meanley 1966, p. 
158-159) : 

In the Ocmulgee River floodplain forest near Macon, the nesting species 
in closest association with the Swainson's Warbler were the Cardinal (Rich- 
mondena cardinalis), Hooded Warbler (Wilsonia citrina), and the White- 
eyed Vireo (Vireo griseus). All three nested in or on the edge of canebrakes 
as well as in other plant associations. The Cardinal fed mainly along the 
edge of cane thickets and in forest openings such as logging roads. The 
Hooded Warbler, which fed regularly from 2 to 30 feet above the ground, 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 33 

ranged through the more open growths of cane as well as the more open 
parts of the forest undergrowth. The White-eyed Vireo preferred mostly 
a less homogeneous habitat, more often the edge of viney thickets, and 
usually fed from 5 to 20 feet above the ground. 

Other species, present in canebrakes but not so closely associated with the 
Swainson's Warbler, were the Carolina Wren (Thryothorus ludovicianus), 
Kentucky Warbler (Oporornis formosus), Rufous-sided Towhee (Pipilo 
erythrophthalmus) , and Prothonotary Warbler (Protonotaria citrea). The 
Carolina Wren ranged throughout the floodplain forest, especially about old 
logs and brush piles. The Kentucky Warbler occurred most often where 
there was a denser ground cover, particularly of herbaceous plants, than in 
the canebrakes. The Towhee, a ground-feeder like the Swainson's and Ken- 
tucky Warblers, fed in the canebrakes but usually where the leaf litter and 
cover was thicker than in the areas used by the Swainson's Warbler. The 
Towhee also fed in other parts of the forest and in the edge of habitats. The 
Prothonotary Warbler preferred the banks of streams that flowed through 
the canebrakes and the vegetation along the banks. 

During migration, Worm-eating Warblers and Ovenbirds (Seiurus auro- 
capillus) moved through the canebrakes as well as other parts of the flood- 
plain forest. 

The Great Dismal Swamp 

This extensive southern swamp a few miles south of Norfolk, 
Va., covers an area of about 600,000 acres in Nansemond and 
Norfolk Counties, Va., and in Pasquotank, Gates, and Camden 
Counties, N.C. In 1968 the Swamp was still a great wilderness, 
but with no virgin timber remaining. The part of the Swamp in 
which the Swainson's Warbler occurs is generally devoid of sur- 
face water (but low and damp) owing to drainage in connection 
with logging operations during the past 200 years. Being on low 
flat land with a high water table, some Swainson's Warbler terri- 
tories are partially inundated after heavy rainfall. 

The Dismal Swamp is quite diversified floristically but in the 
past apparently was predominantly forested with swamp black- 
gum (Nyssa silvatica var. biflora) (Kearney, 1901). It is in the 
remnant of this forest type, now of mixed species composition, 
that the Swainson's Warbler is mainly found today. 

I examined such a mixed forest community along the northern 
end of Jericho Ditch (fig. 14), about 3 miles southeast of Suffolk, 
Va., in June 1966 and found that it was composed of the following 
plants : Predominant trees of the upper canopy were swamp black- 
gum, red maple (Acer rubrum), sweetgum, willow oak (Quercus 
phellos), water oak, tulip poplar (Liriodendron Tulipifera); 
lower trees were American holy (Ilex opaca), paw-paw (Asimina 
triloba), swamp magnolia (Magnolia virginiana) , and red bay 
(Persea borbonia); undergrowth was mainly sweet pepperbush 
and greenbrier, but netted chain-fern (Woodwardia areolata) 



34 



NORTH AMERICAN FAUNA 69 










v-^Imt 






Figure 14. — Mixed swamp hardwood habitat in the Dismal Swamp in south- 
eastern Virginia, 1968. Major forest species are swamp blackgum, sweet- 
gum, and red maple. Note Swainson's Warbler nest 2 feet from the ground 
in sweet pepperbush, center of picture. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 



35 



covered the ground where there was more light. The Swainson's 
Warbler foraged mostly in openings between clumps of sweet 
pepperbush and greenbrier and in the small pure stands of 
sweet pepperbush. It nested mostly in the greenbrier tangles. A 
community of this composition also is the major Swainson's 
Warbler habitat in the Pocomoke Swamp on the Eastern Shore of 
Maryland. 

I counted eight territorial males along a 0.5-mile transect in the 
vicinity of the Virginia-North Carolina line on April 20, 1958. 
Bird associates during the breeding season in the sweet pepper- 
bush-greenbrier undergrowth are the White-eyed Vireo, Prothono- 
tary Warbler, Prairie Warbler (Dendroica discolor), Ovenbird, 
Hooded Warbler, and Cardinal. The presence of the Prairie War- 
bler in this habitat was most unexpected, since nowhere else have 
I encountered it breeding in closed-forest habitat. An interesting 
breeding bird of this same swamp forest, but at higher elevations, 
is Wayne's Black-throated Green Warbler (Dendroica virens 
waynei) . 

Bayou Boeuf Swamp, La., and Monkey John Swamp, S.C. 

Observations were made in the scrub palmetto breeding ground 
habitat in Bayou Boeuf Swamp near Alexandria, La., in the spring 
of 1956 and 1957, and in Monkey John Swamp near Savannah, 




Figure 15. — Part of scrub palmetto territory of a male Swainson's Warbler 
in Monkey John Swamp, Jasper County, S.C, May 1964. 



36 NORTH AMERICAN FAUNA 69 

Ga., (fig. 15) in the spring of 1964. The physical features of these 
two areas were quite similar. Red ash, American elm, water oak, 
sweetgum, and hackberry formed an important part of the forest 
in both areas. 

In Monkey John Swamp the density of the combined layers of 
the upper canopy and lower trees was about 90 percent. The 
undergrowth, almost entirely scrub palmetto, averaged about 3 
feet in height, with about 800 plants per acre. Most of the ground 
area beneath the palmettos was dry. Wet spots under the palmettos 
in the territory of a Swainson's Warbler were generally avoided. 

In the scrub palmetto habitat of Bayou Boeuf Swamp, I found 
a population density of 10 territorial males per 100 acres in April 
1957. 

Western Kentucky 
R. M. Mengel (1965, p. 69) states that the ridge bottoms — 

the driest habitat of the alluvial forests, contain the finest broadleaf forest 
and the richest small bird populations of the region. It is in such areas that 
Swainson's Warbler is most numerous. 

These are the cane ridges so favored by the Swainson's Warbler 
in the lower Mississippi Valley. 



SOUTHERN APPALACHIANS 

In the Southern Appalachians the Swainson's Warbler is pri- 
marily associated with the moist lower slopes of mountain ravines 
and various drainage systems of the Mixed Mesophytic Forest 
Region. On these lower slopes, where the proportion of hemlock 
in the mesic forest increases, rhododendron is often the main 
understory species ; and it is within this association (figs. 16-17) 
that the warbler is most often found. It also occurs in some cove 
hardwood forests (fig. 18), where the understory may be com- 
posed of a heterogeneous growth of deciduous shrubs, and in other 
habitats. 

In areas where the Swainson's Warbler is locally common, indi- 
viduals of a population may "spill over" from optimum to marginal 
habitats, as cited by Brooks and Legg (1942, p. 70-80), who in 
West Virginia found a singing bird near the top of a ridge in a 
thicket beneath dead chestnut (Castanea dentata) trees. Parnell 
and Quay (1964, p. 139) reported a few Swainson's Warblers in 
dry sites, such as an oak-hickory forest in Toxaway Gorge in 
western North Carolina. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 37 

■■■■■■ 




Figure 16. — Rhododendron-hemlock association. Mountain breeding habitat of 
the Swainson's Warbler along Collison Creek, on the Allegheny Plateau, 
Nicholas County, W. Va., May 15, 1966. 



38 



NORTH AMERICAN FAUNA 69 




Figure 17. — Mountain breeding habitat, Collison Creek, Nicholas County, 

W. Va. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 39 




:-. 



Figure 18. — Mature mountain cove hardwood habitat of the Swainson's 
Warbler near Charleston, Kanawha County, W. Va., May 1965. Tulip 
poplar is the dominant plant species. 



Allegheny Plateau in W est Virginia 

In West Virginia the Swainson's Warbler is best known from 
the rugged Allegheny Plateau region of the south-central and 
southwestern part of the State. Studies of its habitats have been 
concentrated mainly in the Mt. Lookout section of Nicholas County 
along the Gauley River drainage (Brooks and Legg, 1942), and 
at Charleston in the Kanawha River area (Sims and DeGarmo, 
1948). 

In the Mt. Lookout region Brooks and Legg (1942, p. 78-79) 
found Swainson's Warblers in virtually all areas containing 
tangles of rhododendron, mountain laurel (Kalmia latifolia), hem- 
lock, and American holly. In May 1940 they recorded 10 or 11 
singing males within 1.5 miles along Franzy Creek, a small branch 
of Collison Creek. 

On the south side of the Kanawha River, in Donley Hollow, 
at the edge of the city of Charleston, Eleanor Sims found 18 
Swainson's Warbler nests during 1945-47 (Sims and DeGarmo, 
1948, p. 1). This is a rather good indication of the local abundance 
of the species in this section of the Allegheny Plateau. 

At the foot of the mountain where Donley Hollow meets the 
floodplain the elevation is only 600 feet. As one travels up the 



40 



NORTH AMERICAN FAUNA 69 




Figure 19. — Umbrella magnolia, prominent understory tree in habitat of the 
Swainson's Warbler near Charleston, W. Va. 

ravine beside Donley Branch and climbs several hundred feet 
higher, Swainson's Warblers can be heard singing on both forested 
slopes, often two or three hundred feet up from Donley Branch. 
I counted seven singing males as I walked a mile up the hollow 
on May 15, 1965. There are probably fewer birds in the hollow 
now than at the time Sims and DeGarmo made their study, 
since the lower, moister slopes are now occupied by suburban 
residences. 

The Donley Hollow habitat is like a Costal Plain floodplain 
forest on the side of a hill. In these moist hollows or mountain 
ravines the dominant canopy species of the mature cove hard- 
woods forest is tulip poplar. The diameters at breast height of the 
four largest tulip poplars in one Swainson's Warbler breeding 
territory in 1965 were 25, 30, 33, and 36 inches. Other trees of 
the upper canopy layer were mainly beech (Fagus grandifolia) , 
buckeye (Aesculus sp.), black oak (Quercus velutina), red maple, 
and sweetgum. Lower trees were umbrella magnolia (Magnolia 
tripetala) (fig. 19), dogwood (Cornus florida), and paw-paw. The 
undergrowth was mainly spicebush (hinder a benzoin), with oc- 
casional thickets of greenbrier and Japanese honeysuckle 
(Lonicera japonica). Thinly distributed herbaceous plants of the 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 41 

ground flora were nettle (Laportea canadensis), mayapple 
(Podophyllum peltatum), violet (Viola sp.), baneberry (Actaea 
sp.), and Christmas fern (Polystichum acrostichoides). Twenty 
exposure meter readings at Swainson's Warbler feeding sites 
ranged from 50 to 245 footcandles. 

The closest avian associates of the Swainson's Warbler in this 
habitat are the same as in most Coastal Plain breeding localities : 
the White-eyed Vireo, the Hooded and Kentucky Warblers, the 
Cardinal, and the Rufous-sided Towhee. 

Toxaway River Gorge 

Parnell and Quay (1964) found the Swainson's Warbler to be 
a common summer resident in Toxaway River Gorge, Transyl- 
vania County, N.C., in the summer of 1961. This section of south- 
western North Carolina is in the part of the Southern Appala- 
chians where North Carolina, South Carolina, and Georgia come 
together. There are breeding records from the mountains of all 
three States. 

In Toxaway Gorge, Swainson's Warblers were found at alti- 
tudes of 1,200 to 2,800 feet. According to Parnell and Quay (1964, 
p. 144), these birds — 

showed a preference for dense stands of rhododendron, mountain laurel, and 
dog hobble (Leucothoe editorum) along the narrow riverbottom Pine Flats. 
The Mixed Mesophytic Coves and Slopes and the Oak Forest were utilized 
to a lesser degree. 

The Pine Flats are generally more mesic, more mature, and less 
disturbed than the other habitats. Canopy species are white pine 
(Pinus strobus), Virginia pine (Pinus virginiana), hemlock, and 
tulip poplar. The understory is mainly rhododendron. The Mixed 
Mesophytic Cove and Slope Forest canopies included such species 
as red maple, sweet birch (Betula lenta), hemlock, beech, bass- 
wood (Tilia americana), and tulip poplar. They have poorly de- 
veloped shrub layers, but local thickets of rhododendron and laurel 
occur. The sparsity of Swainson's Warblers in this forest type 
may be due to the poorly developed shrub stratum. The Oak 
Forest gradually becomes differentiated from the Mixed Meso- 
phytic type as the sites become drier. Mountain laurel is the main 
Oak Forest understory species. 

Most of the same avian associates of the Swainson's Warbler as 
in the Coastal Plain and other localities of the Southern Appala- 
chians are found in Toxaway Gorge. Parnell and Quay (1964, p. 
145) list the Worm-eating Warbler (Helmitheros vermivorus) as 
an associate of the Swainson's Warbler. The Worm-eating War- 



42 NORTH AMERICAN FAUNA 69 

bier is also a nesting associate in the Pocomoke Swamp in Mary- 
land, in the Arkansas River bottoms near Gillett, Ark., and at 
Charleston, W. Va., Mountain warblers breeding in the Toxaway 
Gorge included the Black-throated Blue (Dendroica caerulescens), 
the Black-throated Green (Dendroica virens), the Chestnut-sided 
(Dendroica pensylvanica) , the Canada (Wilsonia canadensis), 
and the Blackburnian (Dendroica fusca). 



Description 

SIZE 

The Swainson's Warbler is a rather short and stocky bird. Its 
length, 5 to 5!/2 inches, is about average for warblers, but it is 
heavier than most of the Dendroicas and Vermivoras. Four males 
collected during the breeding season weighed 13.2, 15.4, 16.2, and 
16.6 grams (Mengel, 1965; Norris and Johnston, 1958; and L. C. 
Binford, Louisiana State University Collection). Two females 
taken in winter, one in Quintana Roo, Mexico, and one in British 
Honduras, weighed 13.7 and 13.9 grams (L. C. Binford and S. M. 
Russell, Louisiana State University Collection). A live male at 
Andros Island, Bahamas, in March, weighed 15.6 grams (Walkin- 
shaw and Walkinshaw, 1961). 

A series of birds that struck a Tallahassee, Fla., TV tower in 
spring migration averaged lighter than those striking the tower 
in the fall. The mean weight of the spring series of 15 birds was 
14.9 grams, whereas the mean weight of the fall series of 19 was 
18.9 grams (table 1). The Tallahassee TV tower is less than 50 
miles from the Gulf Coast, and birds coming in from a trans-Gulf 
or circum-Gulf migration would have used up much of their re- 
serve fat; whereas those leaving the United States would have a 
large fat reserve for the long journey to the wintering ground. 
Norris (1963, p. 47) reported that two birds that struck a TV 
tower in the Savannah River Valley in South Carolina on Septem- 
ber 24, 1957, were excessively fat : one was recorded as having 19 
percent fat, and the other, 24 percent. 

Table 1. — Weights of Swainson's Warblers killed at TV tower, Tallahassee, 

Fla., during migration 

[In grams] 

Spring Fall 

(15 specimens) (19 specimens) 

Minimum . 

Maximum i 

Median __ 

Standard deviation 



11.3 


14.3 


15.7 


20.4 


14.9 


185 


13.9 


18.3 


±1.2 


±1.7 



48 



44 NORTH AMERICAN FAUNA 69 

Measurements in millimeters of 11 male specimens collected 
during the breeding season on the Coastal Plain are as follows : 
Wing, 3 67.5-72.5 (70.2) ; tail, 46.5-52.0 (49.1) ; exposed culmen, 
15.0-16.5 (15.3) ; tarsus, 17.0-19.0 (17.8) ; middle toe, 12.5-14.0 
(13.2). Measurements in millimeters of 10 female specimens col- 
lected during the breeding season on the Coastal Plains, are: 
Wing, 66.0-72.0 (69.0) ; tail, 46.5-52.0 (49.4) ; exposed culmen, 
14.8-16.0 (15.3) ; tarsus, 17.5-19.0 (18.2) ; middle toe, 13.0-14.0 
(13.3). 

DISTINGUISHING CHARACTERS 

Sexes of the Swainson's Warbler are alike. Upperparts, includ- 
ing wings, are brown, except the crown which is reddish brown ; 
underparts are yellowish-white and unstreaked. There is no white 
in wings or tail. The bill is large, thick at the base, and sharply 
pointed. 

Similar species. — The Worm-eating Warbler has black stripes 
on its crown. The Ovenbird is streaked below. Immature Con- 
necticut Warblers (Oporomis agilis) and Mourning Warblers 
(Oporomis Philadelphia) in fall plumage have eye rings. 

ADULT PLUMAGE 

The crown of the Swainson's Warbler varies from almost cin- 
namon to chocolate brown, with a barely distinct buffy median 
stripe from the base of the culmen through the forehead. There is 
a white or pale yellowish supercilliary (eye) stripe, a dusky spot 
in front of the eye, and a brownish postocular streak. The sides 
of the head are otherwise pale buffy brownish. Back, scapulars, 
rump, upper tail coverts, tail, and wing coverts are olive brown 
or olive-grayish brown. Tertials are warmer brown (toward 
mummy or prouts brown) ; secondaries and primaries are dusky, 
edged with brown. (The closed wing appears browner than the 
back). Underparts are yellowish white to nearly plain white 
(possibly geographic variation), shaded with olive or olive- 
grayish on the sides. Adults in autumn are indistinguishable from 
breeding birds. 

The bill is brownish, except the undersurface of the lower 
mandible, which is flesh colored. The iris is brown. Legs and feet 
are of a pale (pinkish) flesh color. The culmen is slightly curved, 
narrowed, and elevated between the nostrils. The foregoing de- 
scription of plumage and soft parts is partly from R. Ridgway 
(1902 p. 436-437). 



3 Wing measurements are for the chord, from bend ol wing to tip of longest primary. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 45 

JUVENILE PLUMAGE 

The juvenile wings and tail are similar to those of adults. 
Upperparts are brown; throat and chest are dark brown; and 
other underparts are mottled brown and white. There is no 
whitish line over the eye. 

GEOGRAPHIC VARIATION 

Breeding birds from the Southern Appalachians differ from 
Coastal Plain birds in that underparts tend to be whiter (less 
tinged with yellow) . The underparts of 15 Coastal Plain specimens 
in breeding plumage were primrose yellow ; whereas seven moun- 
tain specimens in breeding plumage were almost immaculate 
below but had a light suffusion of napthalene yellow on breast and 
abdomen. There is no significant size difference between these two 
forms. 

The mountain form was described as a new subspecies by B. 
Meanley and G. M. Bond (1950, p. 191-193) and is known as 
Limnothlypis swainsonii alta (Appalachian Swainson's Warbler). 
The type specimen, adult male, United States National Museum 
No. 362424, was collected at Walhalla, S.C., on June 25, 1940, by 
W. M. Perrygo and S. Y. Hoyt (original number 4,681). 

MOLTING 

Virtually nothing is known of the molt of this species. M. G. 
Vaiden (1940, p. 126) collected a male in partial molt on July 17, 
1939, in Sunflower County, Miss. 



Breeding Biology 

TERRITORIAL BEHAVIOR 

Arrival on the breeding grounds 

The Swainson's Warbler is one of the last of the southern 
warblers to arrive on the breeding grounds, but it is earlier than 
most of the northern transient members of the family. When I 
visited the Dismal Swamp on April 11, 1969, all of the resident 
breeding warblers except the Swainson's Warbler had returned. 
Wayne's Black-throated Green Warbler had already begun to 
nest. Since the foliage was only about one-third out, and since 
Swainson's Warbler occupies the shadiest part of the swamp, its 
late appearance is probably timed with that of the foliage. 

Since males sing the first day on the breeding grounds, the 
schedule of their arrival is better known than that of females; 
but females have struck the TV tower at Tall Timbers Research 
Station, Tallahassee, Fla., as early as the first week in April (Wil- 
liam Dopson and James B. Cope, personal communication). At 
the Dismal Swamp in southeastern Virginia, earliest males have 
been recorded as arriving on April 15. On April 20, 1969, I ob- 
served a mated pair on their breeding territory in this swamp. 

In the relatively late season of 1966, at my Macon, Ga., study 
area, the local male population arrived during a period of about 1 
week. The first four males arrived on April 12 ; by the next morn- 
ing there were eight males ; there were nine on the 14th, and ten 
on the 15th, the date I departed from the area. When I returned 
on April 28 there were 19 males in the area. Apparently the males, 
and probably the females, arrive at night. I was on the breeding 
grounds 2 whole days preceding the arrival of the first males on 
the 12th, and on that morning I was there before dawn. At day- 
break on April 12, I heard the first Swainson's Warbler. 
Homing 

Individuals that establish a territory one year may return to 
the same place in succeeding years. John Weske banded a Swain- 
son's Warbler on territory in the Pocomoke Swamp in Maryland 
in May 1960, and the bird was recovered at virtually the same 
place the following four seasons by mist-netters David Bridge and 
Vernon Kleen. In my study area in the Dismal Swamp, a marked 
male occupied the same general territory for 3 successive years. 

46 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 47 



Figure 20. — Overlapping territories occupied by the same (marked) male 
Swainson's Warbler for three successive years (1966, 1967, 1968) in the 
Dismal Swamp in Virginia. 

Territories 

Males establish territories soon after arrival on their breeding 
grounds. The size and distribution of territories in an optimum 
area may depend upon the extent and arrangement of the habitat, 
as well as upon competition with other male Swainson's Warblers 
for food and space. Where prime habitat is limited in extent, it 
may support several territories, thus creating a group or "colony" 
of birds. This situation frequently occurs in southern canebrakes 
and is not unlike breeding "colonies" of the Kirtland's Warbler 
(Dendroica kirtlandii) in Michigan jack pine (Pinus Bankisiana) 
habitat. In a 7-acre canebrake in the Ocmulgee River floodplain 
forest near Macon, Ga., there were four territories, and not all 
of the canebrake was occupied. 

Sprunt and Denton (in Griscom and Sprunt, 1957 p. 51) re- 
ported that four territories in Georgia ranged in size from 0.72 
to 0.91 acre (table 2). Two of the territories were adjacent and 
two were not. The smallest territory that I measured at Macon 
contained only 0.3 acre (table 2). It was in a block of woodland 
approximately 2 acres in size and was separated from the main 
forest by a cleared powerline right-of-way 50 yards wide. 

In the Dismal Swamp, prime habitat is spotty; the territories 
are farther apart and larger than in the Ocmulgee River flood- 
plain forest, where optimum habitat often occurs in larger blocks. 
The territory of one paired male in the Dismal Swamp covered 



48 NORTH AMERICAN FAUNA 69 

nearly 6 acres, and that of another nearly 4 acres (table 2). The 
overlapping territories occupied by the same Dismal Swamp male 
in 1966, 1967, and 1968 (fig. 20) contained 4.8, 1.7, and 1.6 acres 
respectively. In contrast, territories in the floodplain forest cane- 
brakes seldom exceeded 1 acre. In two Dismal Swamp territories, 
only a part of each defended area was suitable for feeding and 
nesting; whereas in the canebrakes virtually all of the defended 
area was utilized for feeding. The "excess" area of the Dismal 
Swamp territories is used mainly for singing, but it is also 
defended. 

Sometimes in discontinuous habitat a male may occupy a split 
territory or a territory composed of separate segments. One such 
territory in Monkey John Swamp, a few miles north of Savannah, 
Ga., had three segments. Two of the segments were on opposite 
sides of a cypress (Taxodium distichum) pond; the third was 
across a road from the pond. The occupied segments totaled 0.6 
acre (table 2) . 

Table 2. — Size of Swainson's Warbler territories 



Size 
Locality (acres) 


Reference 


Ocmulgee River bottom, Bibb County, Ga. 0.3 .. 

Monkey John Swamp, Jasper County, S.C 0.6 

Savannah River bottom, Richmond County, Ga. 0.72.. 
Do. 79 


..Meanley, 1969, p. 247. 

Do. 
..Griscom and Sprunt, 1957, p. 51. 

Do. 


Ocmulgee River bottom, Bibb County, Ga. . 0.83- 


Do. 


Little River Swamp, Tift County, Ga. 0.91 .. 


Do. 


Dismal Swamp, Nansemond County, Va. 1.7 .. 

Tin, 3,9 


..Meanley, 1969, p. 247. 
Do. 


Do, 4.8 .. 


Do. 





Males may remain in the same area for most of the summer. 
One marked Arkansas male occupied the same territory for at 
least 4 months (April 15 to August 15). Six males occupied the 
same territories in my Dismal Swamp study area from April 20 
to at least June 30, the date of my last visit that season. 

However, shifting of boundaries takes place from time to time, 
and the size and shape of territories change. In the Dismal Swamp 
where Swainson's Warblers have plenty of room to spread out 
because of low population densities, and where territories are 
seldom contiguous, a territory may retain its identity throughout 
the breeding cycle. 

During various phases of the breeding cycle different parts of 
the territory may receive major use, but the original territory 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 



49 



established by the male shortly after arrival on the breeding 
grounds may be defended at any time. When the male is not paired 
he uses most of the territory. If the first nest is destroyed, and 
the male and female become separated before the start of a 
second nesting attempt, the whole territory may be used. The part 
used is smallest during the mating and nest-building periods 
(fig. 21), and sometimes during egg-laying. Stenger and Falls 



POWE R 



LINE 




64 feet 



Figure 21. — Variation in size of the territory of a male Swainson's Warbler 
during breeding season. Only the hatched area (with densest cover) was 
occupied during the courtship and mating period. Dismal Swamp in 
Virginia, April 1969. 



(1959, p. 136) found that the area utilized by Ovenbirds was 
larger during the premating, mating, incubation, and nesting 
periods than during nest-building and egg-laying. 

Swainson's Warblers usually occupy larger territorial areas 
during the first few days after their arrival on the breeding 
grounds ; and after the nesting season males that remain on their 
territories may extend the boundaries considerably. A male in the 
Dismal Swamp that occupied 4.1 acres in May and June occasion- 
ally extended his range over an 8-acre area in July. 

The size and shape of a territory changes during each nesting 
attempt, because a different nest site is chosen each time and the 
sites may be several hundred feet apart. The male gives the nest 
site a wide berth when the female is incubating, thus giving the 
appearance that the nest is out of the territory when actually it is 
inside near the edge. The part of the territory most frequented by 
one Dismal Swamp male during a first nesting attempt was 



50 NORTH AMERICAN FAUNA 69 

avoided during the second nesting when the female built her nest 
there and started incubating. 

Defense of territories 

Territories are defended by singing, chasing, and combat. The 
song signals ownership, and each male's primary advertising song 
is usually different from his neighbor's. 

Paired males appear to be more aggressive than unpaired males 
and usually initiate border encounters, which most often take 
place along territory boundaries. A paired and an unpaired male 
with adjacent territories at Macon, Ga., contended each time at 
virtually the same point along the boundary. As these males 
chased each other along the boundary, the paired female was 
close by but remained 10 to 15 feet within her territory, chipping 
excitedly. 

A territorial male with an incubating mate at Pendleton Ferry, 
Ark., apparently had more time for hostile activity and thus was 
involved more often than the Macon paired male, which I observed 
during preincubation traveling with his mate. The Pendleton 
Ferry male would fly from any point in his territory deliberately 
to start a fight at the mutual boundary. He always began chipping 
excitedly as he moved toward his neighbor's territory, and both 
males chipped constantly during border clashes. In addition to 
chasing, the birds fluttered about on the ground after making 
contact and sometimes flew together a few feet up from the 
ground, grasping each other's bill. 

Sometimes when a male invades a neighbor's territory and is 
chased out, he may perform a display on his side of the boundary. 
Such displays most often occur immediately after prolonged en- 
counters. The wing and tail feathers are spread laterally (fig. 22), 
and the tail is vibrated. The bird sidesteps back and forth along a 
branch, frequently turning around, all the time chipping ex- 
citedly. Ficken and Ficken (1962, p. 110) observed a similar dis- 
play in the Redstart (Setophaga ruticilla). At the end of a chase 
in which its adversary is evicted from the territory, a Swainson's 
Warbler male may fly up to a perch and sing vigorously for 10 to 
15 seconds. 

Following boundary encounters, males drift back into their 
territories and usually sing unbroken courses of songs for several 
minutes. Sometimes they start singing close to the boundary, in 
which case songs are incomplete, consisting only of the first two 
or three notes. Then as they move farther into their respective 
territories, they sing more complete songs. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 51 




5. A. Brings 



Figure 22. — Display of a male Swainson's Warbler during or immediately 
following a boundary dispute with a neighboring male. The display re- 
sembles a female soliciting copulation. The wings are quivered, the tail 
feathers are alternately spread and closed, and the bird may step sideways 
back and forth along the limb. 



There is usually little antagonism toward other species, and 
vice versa. White-eyed Vireos, Prothonotary Warblers, Hooded 
Warblers, Cardinals, and occasionally other species nest in terri- 
tories of the Swainson's Warbler and, like the Swainson's War- 
bler, live close to the ground. On one occasion I saw a Hooded 
Warbler chase a Swainson's Warbler, after which the latter flew 
to a high branch within its territory and sang vigorously for 
about 10 seconds. 

COURTSHIP AND MATING 

I have never been present the minute the pair-bond was formed, 
nor have I witnessed male courtship displays before pair forma- 
tion. 

On one occasion when a female entered a male's territory for 
what I believe was the first time, she was chased for short dis- 



52 NORTH AMERICAN FAUNA 69 

tances but not driven beyond the territory boundary. The action 
of the two birds reminded me somewhat of the well-known sexual 
chase of Red-winged Blackbirds (Agelaius phoeniceus), when the 
females arrive on the breeding grounds. 

During prenesting I observed a display by a paired male where 
he assumed a posture similar to a female ready for copulation. 
The posturing occurred when the male was perched about 3 feet 
from the ground and was approached by the female to within 
about 1 foot. When the female alighted near the male, he uttered 
a faint twee-twee-twee that was barely audible from where I was 
standing less than 8 feet away. The next day under similar cir- 
cumstances, the same male extended his rump feathers only and 
uttered the same faint notes. 

Also during prenesting, a paired male was observed to perform 
a "moth" or floating" flight. I could not locate the female at the 
time. 

Vocalizations 

During the courtship and mating period, a pair spends most of 
the day foraging on the ground, usually within 30 feet of each 
other and often only 2 to 3 feet apart. The male sings very little 
during this period and is otherwise less vociferous than the fe- 
male. He may do some sustained singing early in the morning, 
usually before 7 a.m. I spent 3 consecutive days in the territory of 
one male, and after 7 a.m. on these days he sang four, none, and 
two primary advertising songs. During the day singing was more 
subdued and appeared to be for the purpose of singnaling the 
female when she was momentarily out of contact with the male. 
Sometimes a song was incomplete, consisting only of the first, 
second, or third notes. 

Vocalizations other than song are used by the pair to maintain 
contact. "Chipping" by the female is the most obvious and fre- 
quently used vocalization. Some females chip often enough for 
the investigator to follow a pair during most of the day in habitats 
where he can move about easily. 

The chipping of the female often differs from the conventional 
alarm (chip) notes of both sexes. At times the chip note is more 
subdued, more of a squeak, and toward the end of the vocal 
performance the notes run together into a sort of muted chatter. 
At that point the chipping has the ring of excitement, and has 
attracted the male, who may attempt copulation. 

Sometimes a very faint chip (that I could barely hear at 20 
feet) is used by both members of the pair. This is a single chip, 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 53 

well-spaced and not in a series like constant chipping when the 
birds seem excited. A paired female sometimes utters a faint zeep 
when a male in an adjacent territory sings. 

On one occasion a pair that I had under observation was joined 
by a third bird, presumably a female. The visiting female fed with 
the pair for about 4 minutes, and at no time was chased by the 
male. The paired female chipped constantly while the interloper 
remained. 

Pouncing 

During the mating period males resort to pouncing on the 
females. The male flies to the female, who usually is foraging on 
the ground, and either pecks her rump feathers or pounces on her. 
I observed this behavior for several breeding seasons before I 
was sure that sometimes copulation was taking place. It was 
difficult to believe that copulation could occur under such circum- 
stances. Hann (1937, p. 154) also had difficulty in observing 
copulation during similar behavior by Ovenbirds on the ground : 

When copulation takes place on the ground, it is practically always accom- 
panied by a struggle, which looks more like mortal combat than sexual inter- 
course. The fact that the female does not flee, and may even court the 
procedure, however, dispels any doubt as to her willingness. When they 
emerge from the struggle, the male usually flies to a nearby perch with an 
evident feeling of satisfaction, and the female, after shaking her ruffled 
feathers, proceeds with her eating or nest building. 

Essentially the same behavior is exhibited by the Swainson's 
Warbler. 

Pouncing may occur with or without an "invitation" from the 
female. Most of the time the female appears to be unaware that it 
is going to happen. Sometimes the female's excited chipping im- 
mediately preceeds the stalking and pouncing. 

After observing pouncing behavior a few times, I could always 
anticipate when it was going to happen. The male, feeding on the 
ground, usually within 20 feet of his mate, discontinued feeding 
and mounted a branch or log, usually 6 to 12 inches from the 
ground. Then he remained virtually motionless in a crouched 
position for 1 to 5 minutes, facing and watching the female who 
was foraging on the ground or perhaps preening. In his crouched 
position the flank feathers of the male were slightly fluffed out, 
and his head was drawn in close to his body. Occasionally he 
would slowly move his head slightly to one side. When the female 
moved too far out of range, the male shifted to a closer perch and 
continued his crouched stance. His performance reminded me of 
a cat getting ready to pounce on its prey. He would then fly to 



54 NORTH AMERICAN FAUNA 69 

the female, and the two would flutter together on the ground. 
Sometimes the male stopped short of the female, and sometimes 
when contact was made copulation did not take place. The female 
sometimes responded with a faint tweet-tweet-tweet. Following 
such an encounter, the male might fly off singing a song as loud 
as the primary advertising song but not resembling it. These 
flights were sometimes upward in a sort of spiral. One male I 
watched often sang a whisper song after pouncing. Usually, how- 
ever, the pair started feeding within a few feet of each other and 
near the spot where pouncing occurred. Pouncing is also known 
in the Red Warbler (Ergaticus ruber) (Elliott 1969, p. 188). 

Nice (1943, p. 174-175) reported Song Sparrow (Melospiza 
melodia) pouncing as a form of courtship display "confined 
typically to the early stages of the nesting cycle." The male flies 
down to his mate, collides with her, and then flies away singing. 
Nice states that pouncing by the Song Sparrow early in the season 
has no immediate connection with copulation. 

Pouncing on the mate occurs during the long period while song is inhibited 
and also during building. It may be a technique of the male for impressing 
himself upon his mate during the time of silence, of making his presence 
keenly felt. 

Howard (1929, p. 22) observed that after the sexual chase 
recently paired Yellow Buntings (Emberiza citrinella citrinella) 
flutter together on or near the ground or peck each other as they 
rise in perpendicular flight, like fighting males. Howard believed 
that the sexual chase and pouncing show that the male is ready to 
copulate and that the female is not ready to receive him. 

One male that I watched for 2 days pounced about three times 
each hour ; another that I watched for 3 days before the beginning 
of nest building pounced about once every 10 minutes. A third 
male pounced about once an hour on the day nest building began ; 
nest building was sporadic that day and occurred mostly in the 
morning, for just 2 or 3 minutes following pouncing. 

Copulation occasionally occurs while the female is perched on a 
limb of a shrub or tree. When copulating in this manner the male 
sometimes holds onto the female's crown feathers. 

NESTING BEHAVIOR 

Nesting period 

The prenesting period for paired Swainson's Warblers is rela- 
tively brief, for nesting begins soon after pair formation. For 
example, I visited the breeding grounds in the Dismal Swamp on 
April 12, 1969, at which time the Swainson's Warblers had not 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 55 

yet returned. When I returned on April 20, I found birds paired 
in at least one territory, and by April 23, nest-building had started 
in that territory. 

The earliest nesting anywhere is reported by Wayne (1910, p. 
150) who collected eggs containing small embryos on April 28, at 
Charleston, S.C. However, May 1 is about the average date for 
the beginning of nesting throughout the Swainson's Warbler 
range. 

Nest building at Macon, Ga., and Pendleton Ferry, Ark., started 
about 3 weeks after the first males arrived on the breeding 
grounds. A completed nest ready for eggs was found at Macon 
on April 27, 1946, and nests with full clutches were found by May 
3, 1945. A nest containing one Swainson's Warbler egg and three 
Brown-headed Cowbird (Molothrus ater) eggs was found at 
Pendleton Ferry on May 1, 1967. This nest was probably con- 
structed during the third week in April. 

In the Dismal Swamp the earliest record of nest building is 
April 23, 1969. This is about 8 days after the average arrival date 
of first males. In this same area I observed two nests under con- 
struction on May 1. 

On the Allegheny Plateau near Charleston, W. Va., Sims and 
DeGarmo (1948, p. 4) state, nest building begins about 2 weeks 
after arrival on the breeding grounds. They found a completed 
nest as early as May 1. 

Renestings or second nestings occur throughout June and into 
early July. Perhaps the latest date is a nest with slightly incubated 
eggs found on July 13, 1886, at Savannah, Ga. (Perry 1886, p. 
188). Young from this nest would have fledged about August 1. 

Nest site and materials 

For three or four days before nest building, and possibly longer, 
another activity of the pair is the examining of nest sites. The 
male of a pair that I watched at this activity led the way more 
than his mate, and at times he examined nest sites alone. One 
might therefore conclude that the male selects the nest site. 

The average height of 10 nests in various localities was 4 feet 
inches, with a range of 1 foot 9 inches to 6 feet 3 inches. Nests 
are usually built in the predominant understory vegetation (fig. 
23). In the Dismal Swamp, nests are frequently placed in green- 
brier vines (fig. 24), as well as in Japanese honeysuckle, sweet 
pepperbush, and switch cane (Arundinaria tecta). 

Most nests in my Dismal Swamp study area were located within 
30 feet of a road or path. Vegetation in these situations is denser 
because of better exposure to light. 



56 



NORTH AMERICAN FAUNA 69 



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»<!> 


i-: f 




■ ** Jfl| 




nj'i'-~ 


&"■ 


A 


d 


Rk ■ WS !^fi?F\iS 




I 


/,i 


VA 1 






fc^ 


fa 


^| 


■ 


^BS*«£^ 


vd it 




.#1 L i 
\ 




2^T (' 




. Hi 


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S 


," 


S- 




n ' 




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- r 





Figure 23. — A Swainson's Warbler incubating during flood stage in Ocmul- 
gee River floodplain forest near Macon, Ga., May 1946. Water is 3 feet 
deep. 



In Bayou Boeuf Swamp in central Louisiana, one nest in a scrub 
palmetto thicket was placed in a blackberry vine in such a way 
that it was directly beneath the broad frond of a scrub palmetto. 
The nest was completely shielded from above as if it had a roof 
over it 4 inches from the rim. 

In a canebrake the nest is rarely located in the densest part of 
the stand, but is usually nearer the edge where the stand is thin- 
ner and the cane poles are smaller. In a mature mountain cove 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 57 




Figure 24. — Swainson's Warbler nest in greenbrier vine, 2 feet above the 
ground, Dismal Swamp in Virginia. 

hardwood forest at Charleston, W. Va., Sims and DeGarmo (1948, 
p. 4) found that — 

the bird avoids placing the nest in dense cover, yet in all instances, a patch 
of some type of such cover is within a distance of twenty-five to fifty feet. 
In many cases, this thicket is a growth of greenbriar but may be grape, 
honeysuckle, blackberry or bittersweet. There, appears to be a definite effort 
to locate the nest in such a manner that it is in close proximity to a screen 
of protective cover. 

All nests that I found in territories of known boundaries were 
inside the territorial borders. However, they were often near the 
edge, or the male spent most of his time in an area to one side of 
the nest. Sprunt and Denton (in Griscom and Sprunt, 1957, p. 51) 
had this to say about the location of the nest in the defended 
territory : 

The territory defended by the male is used primarily for mating and 
feeding and not for nesting. The nest itself is usually located along the 
margin of the territory but may be entirely outside of it . . . 



58 



NORTH AMERICAN FAUNA 69 



I wonder whether Sprunt and Denton's observations were not 
made during the incubation period when most males avoid the 
nest site, which is often near the edge of the territory, thus giving 
the impression of being outside it. When the eggs hatch, the male 
attends the young along with the female; then the territory no 
longer has a buffer zone. 

The Swainson's Warbler builds a large and bulky nest (fig. 25), 
apparently larger than that of other warblers that nest above the 
ground. Of two nests, in Dismal Swamp, that I saw under con- 
struction from the beginning, one took 2 days and one 3 days to 
complete, and they were built entirely by the females. At one site 
the male was often close by but visited the nest no more than 
twice each day during the 3 days of construction ; the male did not 
assist in construction and apparently visited the nest in search 
of the female. At the other site, during the initial stages of con- 
struction the male occasionally accompanied the female to the 
nest as she flew in with nesting materials; he brought along no 
material and left almost immediately after arriving at the nest. 

At both these Dismal Swamp nests the female did virtually all 
of the building before noon. Building of the nest that I watched 




Figure 25. — The large, bulky nest of a Swainson's Warbler (right) and the 
nest of a nesting associate, the Cardinal, a species nearly twice the size of 
the warbler. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 59 

more closely took parts of 3 days, mostly between 7 and 11 a.m. 
Building was resumed in the late afternoon of each day between 
4 and 5 p.m. However, during the late afternoon building period 
no more than half a dozen trips were made to the nest each day. 
The female made between 100 and 125 trips each morning. From 
9:25 to 10 a.m. one morning, she made 34 trips, an average of 
about one trip a minute. During any sustained period she spent an 
average of 24 seconds at the nest, with a range of 9 to 70 seconds. 
The female sometimes chipped a few times while working on the 
nest. During the nest-building period, her mate rarely sang after 
8 a.m. 

All nest materials were gathered from the ground within 30 
feet of the nest. Dry leaves, used in the bulky part of the nest 
and the outer layer, were obtained from the drier part of the 
woods ; the cypress needles and red maple flower pedicels used in 
the lining came from a wet spot near the nest site. 

Nests are constructed of a rather wide assortment of materials, 
but there is a selection of certain plant parts. The number of 
species of plants represented in a nest depends somewhat on the 
composition of the forest in which the nest is located. There sel- 
dom were more than a dozen species of plants in the nests I ex- 
amined. The number of plant pieces in a Pendleton Ferry, Ark., 
nest totaled 418; there were 323 in a Dismal Swamp nest. The 
most pieces were in the lining of the cup. Sticks are seldom used 
in nests, and the few that occur seem almost incidental. But the 
first of three nests built by a female in a single season in the 
Dismal Swamp contained a great many sticks, which is the reason 
why it weighed more than the second and third nests. 

In canebrakes the foundation of a nest is often a bunch of dead 
leaves that have lodged in the axils of a cane stalk. The Dismal 
Swamp female that built three nests used the relatively large 
leaves of the swamp magnolia as a platform for each of them. 
Each was at a site where several greenbrier vines crossed a hori- 
zontal limb of a shrub, so that the half dozen magnolia leaves 
formed a rather level base. Deposited upon these magnolia leaves 
were dried leaves, sticks, vines, and tendrils that formed the 
rather loose outer layer of the nest. Most of the leaves were 
swamp magnolia, red maple, red bay, and greenbrier. Most of the 
sticks were greenbrier. 

The next layer was more compact, consisting almost entirely 
of decomposed or skeletonized leaves of the swamp magnolia. 
This layer formed the outer shell of a cup composed of finer 
materials in which the eggs were deposited. In positioning the 



60 NORTH AMERICAN FAUNA 69 

leaf skeletons, their tips were drawn toward the rim at a grad- 
ually sloping angle to the curve of the cup. All of them were placed 
in a regular pattern, being drawn clockwise from near the base 
on one side of the cup to emerge and protrude from the rim almost 
at the opposite side. All of the protruding petioles thus pointed 
away from the circle of the rim at a narrow angle. This layer 
was constructed similarly in all three nests. Swamp magnolia 
leaves, being enlongated in shape, are well suited for this part of 
the nest structure. 

Next to the layer of magnolia leaves was a layer of cypress twigs 
with needles. Cypress twigs and needles were also used as a lining 
for the upper inside half of the cup and for the rim of the nest. 
The lower inside half and bottom of the cup were lined mostly 
with pedicels of red maple flowers. All 11 of the Dismal Swamp 
nests were lined with these pedicels. Apparently they are a pre- 
ferred item for the lining, since I have also found them in nests 
at Macon, Ga. F. M. Chapman (1907, p. 53) reports that J. N. 
Clark found them in linings of nests of the Worm-eating Warbler 
in New Jersey. 

The Dismal Swamp female that built three nests in one season 
used fewer materials in constructing each succeeding nest; thus 
her nests were progressively lighter ; dry weights were 47.7, 39.8, 
and 26.3 grams. Dimensions of an Arkansas nest were as follows : 
Greatest outside diameter, 15.0 cm.; inside diameter of cup, 4.0 
by 5.0 cm. ; outside depth, 7.8 cm. ; inside depth, 4.2 cm. 

EGG LAYING AND CLUTCH SIZE 

At a Louisiana nest, there was a lapse of 2 days between the 
completion of the nest and the laying of the first egg ; at a Dismal 
Swamp nest there was a lapse of 4 days. Eggs were laid daily 
until the clutches were complete, and incubation began with the 
laying of the last egg in each. At one Dismal Swamp nest the eggs 
were laid in the morning before 7 a.m. By marking eggs, incuba- 
tion period at a nest at Augusta, Ga., was determined to be 14 or 
15 days (J. Fred Denton, personal communication). The incuba- 
tion period of eggs in a nest in the Dismal Swamp in 1969 was 
13 days (F. C. Burford, personal communication). The first egg 
of this clutch of four was laid on May 1, and an egg was deposited 
daily; the first egg was hatching at 6:30 a.m. on May 17. 

Of six first clutches in nests in Georgia, four consisted of three 
eggs each and two had four eggs. Of second clutches in four nests 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 61 

in Dismal Swamp, three had two eggs and one had three. The 
somewhat globular eggs are white (fig. 26), but slightly spotted 
eggs are found on rare occasions (Wayne 1910, p. 149). 




Figure 26. — Nest and eggs of the Swainson's Warbler in cane. 



62 NORTH AMERICAN FAUNA 69 

Cowbird parasitism 

In some parts of its breeding range the Swainson's Warbler 
may be rather heavily parasitized by the Brown-headed Cowbird. 
During the first week in May 1967 at Pendleton Ferry, Ark., I 
located three Swainson's Warbler nests, all of which were para- 
sitized. At one of the nests the warbler was incubating three 
cowbird eggs and one of its own. Three days later it was still 
incubating, but one of the cowbird eggs and its own egg were 
missing. At another one of the nests a warbler was incubating a 
single cowbird egg, and at the third a warbler was incubating 
three cowbird eggs ; evidently the warbler eggs had been removed 
by the cowbirds. 

Kirn (1918, p. 97-98) reported several parasitized nests in 
Copan County, Okla. ; Sims and DeGarmo (1948, p. 5), in the 
course of 3 years, found three of 18 nests parasitized at Charles- 
ton, W. Va. I found that none of 11 Dismal Swamp nests were 
parasitized. Dismal Swamp is near the northern limit of the 
southeastern breeding range hiatus of the cowbird (Webb and 
Wetherbee 1960, p. 83-87), and I found only two or three cow- 
birds during an entire day in the Swamp in the spring of 1968. 
From 1944 to 1946 at Macon, none of six nests were parasitized, 
since at that time the area was out of the cowbird breeding range. 
By 1960, however, cowbirds were commonly breeding there. 

INCUBATION 

Information on behavior during the incubation period was ob- 
tained from a nesting pair in the first week of May at Pendleton 
Ferry, Ark., and from a pair in the Dismal Swamp in the middle 
of June. The Pendleton Ferry pair was the one mentioned above 
whose nest contained three cowbird eggs and one warbler egg. The 
nest was located about 2 feet above the ground between two cane 
poles. The height of the Dismal Swamp nest was also about 2 
feet, and it was placed in a greenbrier vine. At each nest, incuba- 
tion was performed only by the female. 

During incubation the Pendleton Ferry female spent about 78 
percent of her daylight time on the nest. The average period on 
the nest was 70 minutes ; the average period off was 19 minutes. 
The longest period on the nest was 110 minutes, and the shortest 
was 30 minutes. The longest period away from the nest was 25 
minutes ; the shortest was 15 minutes. The Dismal Swamp female 
averaged 54 minutes on and 15 minutes off the nest. Lawrence 
(1953, p. 138), summarizing studies of six wood warblers, found 
that the birds were at the nest 67 to 83 percent of the time. 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 63 

The two females I observed always sat in the same positions 
when incubating. Each left the nest each time in the same direc- 
tion and fed in the same general area. The Pendleton Ferry fe- 
male fed as far as 75 yards from her nest, but usually only about 
30 yards from it. She fed both alone and with her mate. On one 
occasion her mate, which had not sung for more than an hour, 
flew to within 50 feet of the nest and sang two songs. The female 
chipped and left the nest, and the two flew off together to feed. 
Sometimes on leaving the nest the female flew out to about 30 
yards from the nest where she chipped several times, presumably 
to attract her mate. 

Upon returning to the vicinity of her nest, each female in- 
variably chipped two or three times just before settling down. 

The Dismal Swamp female was often fed by her mate when she 
left the nest during the incubation period. She followed the male 
on the ground like a fledgling following its parent. The male, 
walking about with cocked tail, gathered food and presented it to 
her. 

During the several days of my observations, the Pendleton 
Ferry male never visited the nest. He did not come closer than 40 
feet and usually stayed more than 100 feet distant. The Dismal 
Swamp male once, while the female was off feeding, visited the 
nest briefly and, not finding the female there, flew off and began 
singing vigorously. At dusk the Pendleton Ferry male was usually 
seen closer to the nest (40 to 50 feet) than during the lighter part 
of the day. He fed and sang in all areas surrounding the nest but 
was seldom closer than 50 feet. He did not sing as much as an 
unmated male in an adjacent territory. 

CARE OF NESTLINGS 

Most of my information on the care of nestlings is based on 
observations made during a 7-hour period on July 7, 1967, in the 
Dismal Swamp. Between 9:45 a.m. and 4:45 p.m. the 3-day-old 
nestlings were fed 14 times, eight times by the male and six by 
the female. The intervals between feedings ranged from 9 to 59 
minutes. The female was at the nest 53 percent of the time brood- 
ing the young and sometimes standing on the rim. If she was 
brooding when the male came to the nest, she moved to the rim 
while he fed the young. Only the male removed fecal sacs from 
this nest, although at a Macon, Ga., nest the female also removed 
fecal sacs, sometimes swallowing them. 

The male always approached from the same direction and 
worked his way slowly through the undergrowth until he was 2 



64 NORTH AMERICAN FAUNA 69 

to 3 feet beneath the nest; then he hopped up to the rim. The 
female approached from various directions, and flew 20 to 30 feet 
directly to the rim of the nest. On three occasions the male and 
female departed from the nest at the same time. Each time they 
flew in different directions. 

Sims and DeGarmo (1948, p. 5) found that at several West 
Virginia nests young left after 10 days of nest life. At Augusta, 
Ga., the young remained 12 or more days in their nests (Griscom 
and Sprunt 1957, p. 53). Young that I observed at Macon, Ga., 
fledged at 10 days. 

CARE OF FLEDGLINGS 

Fledglings of a Dismal Swamp brood, just 2 days out of the 
nest, were fed only by the female during my 2 days of observa- 
tions (June 13-14, 1967). The male was usually within 100 feet of 
the young and sang much of the time. The three fledglings usually 
did not attempt to follow the parents, but stayed within a rela- 
tively small area where they waited for the female to return with 
food. Most of the time they were perched 6 to 12 inches from the 
ground in heavy cover. During one 2-hour period, two of the three 
fledglings remained close together (5 to 10 feet) within a 20-foot- 
square area ; at other times they were 50 to 100 feet apart. Some- 
times after being fed, a fledgling attempted to hop along after its 
parent, but was soon left behind as the parent flew off in quest of 
food. 

The fledglings were fed an average of every 15 minutes. When 
returning with food the female would walk and hop, rather than 
fly, to the waiting young. The young, hearing the approaching 
female parent rustling through the leaf litter, would intensify 
their chipping as she reached a point about 20 feet from them. 

On three occasions, just as the female was about to feed a 
fledgling, the male pounced on her. As related above, pouncing 
also occurs during the prenesting period after the birds have 
paired. 

Voice 

SONG 

The song of the Swainson's Warbler is loud and ringing and of 
marked musical quality. As Dingle (in Bent, 1953, p. 36) states, 

The bird student who hears the song of Swainson's warbler as he sings in 
his wooded retreat is fortunate, for it is one of the outstanding warbler 
songs and, once heard, leaves a lasting impression upon the listener. At a 
distance it bears much resemblance to the songs of the hooded warbler and 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 65 

Louisiana waterthrush. Close up, however, the appealing quality, lacking in 
the other two, impresses the listener strongly. 

Songs of different individuals of the species vary. I have stood 
in one spot and heard the songs of five Swainson's Warblers, each 
distinctly different. 

The song consists of three or four high introductory notes, all 
separated, followed by a phrase of four or five syllables uttered 
rapidly and slurred (Brooks and Legg, 1942, p. 82). 

The songs of seven birds were analyzed from tape recordings 
made by W. W. H. Gunn (in Griscom and Sprunt 1957, p. 26-27) 
at Charleston, W. Va. Gunn's rendition is as follows : 

tee-o tee-o (tee) whit-sut-say bee-o, or tee-o tee toot-sut-say bee-u, or whee-u 
whee wkit-sut-say bee-o. 

. . . they have louti ringing songs closely resembling those of the Louisiana 
Waterthrush both in tonal quality and phraseology. However, certain char- 
acteristic differences are evident: First, songs of Swainson's Warblers are 
noticeably shorter in duration, being composed of fewer syllables. Then too, 
the slow opening notes comprising the first part of the song differ markedly 
in phrasing between the two species, and although there is a remarkable 
resemblance in the second portion of the song, the Louisiana Waterthrush 
then typically goes on to add a final phrase missing from songs of Swain- 
son's Warblers. 

Gunn says that the duration of the Swainson's song is 1% sec- 
onds and that of the Louisiana Waterthrush's 1^2 to 2 seconds. 

At a distance the strongly accented slurred ending (the first 
note high in pitch, the second low) of the Hooded Warbler song is 
suggestive of the ending of the Swainson's Warbler song, and 
often is confusing. 

Whisper song 

Berger (1961, p. 169) defines the whisper song as "the soft 
inward rendering of the primary advertising song, with or with- 
out variations." Muted or whisper songs of the Swainson's War- 
bler are a continuous chatter or musical twittering that may go on 
for as long as 3 minutes. I have never noticed any resemblance to 
the primary advertising song; rather they sound more like the 
continuous chattering notes of Goldfinches (Spinus tristis) in the 
spring, but are more musical. I have also heard in the spring a 
chattering song of kinglets (Regulus satrapa and R. calendula) 
and Blue-gray Gnatcatchers (Polioptila caerulea) that sounded 
a bit like the Swainson's Warbler whisper song. In the floodplain 
forest canebrakes of the Ocmulgee River in Georgia in April, I 
have heard all four of these species rendering these notes at 
nearly the same time. There have been times when I was not sure 



66 NORTH AMERICAN FAUNA 69 

whether I was hearing a Swainson's Warbler whisper song or 
notes of the other three birds. In fact, the whisper songs of 
several species of warblers sound alike. I have been fooled by the 
Prothonotary Warbler and the Yellowthroat (Geothlypis trichas), 
thinking I was hearing a Swainson's Warbler. 

The whisper song is seldom audible beyond 30 feet. It is given 
throughout the breeding season. Mayfield (1960, p. 127) thought 
that the Kirtland's Warbler sang whisper songs mainly when 
other males were nearby. Morse (1967, p. 497) found that in the 
Parula Warbler (Parula americana) muted and incomplete songs 
were associated with a high level of aggression. I have heard the 
Swainson's Warbler give the whisper song when in the presence 
of other males, following a conflict at a territorial border, when 
alone on an isolated territory, and after pouncing on a female 
just as she was about to feed fledglings. I have heard the whisper 
song of the Swainson's Warbler most often when there was no 
other male or female of the species, or any other bird, nearby. 

The whisper song may be delivered when the bird is standing 
or moving on the ground, perched on a limb, or in flight. I heard 
one male give the whisper song as he flew along about 2 feet above 
the ground for a distance of 50 feet. The whisper and primary 
advertising songs may be alternated : I observed a perched Swain- 
son's Warbler that sang both, preening in between, and then 
hopped to the ground, alternating the songs while foraging. 

Flight song 

I have heard flight songs that had no resemblance to whisper or 
primary advertising songs. They were as loud as the primary 
advertising songs but continuous and run together, and they 
lasted as long as the flight. One singing bird took off from the 
ground in a spiralling flight to a height of about 35 feet ; another 
flew from the ground at a 60-degree angle to a perch 40 feet up. 

Incomplete song 

Incomplete songs — songs without endings and songs consisting 
of only the first, second, or third notes — may be heard at any time 
during the breeding season. As mentioned above, incomplete 
songs are sometimes given following territorial bouts with neigh- 
boring males. They are often heard when a bird is startled or 
frightened. For example, a Dismal Swamp male alternately sang 
only one and then two notes when a Common Grackle (Quiscalus 
quiscula), a nest robber, invaded his territory. 

SINGING BEHAVIOR 

The primary advertising song is sung only by the male, and so 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 67 

are whisper songs, as far as I can ascertain. When singing the 
primary advertising song, the bird changes the position of its 
head more than that of its body. The body is only slightly angled 
upward from the silent perching position; the head is thrown 
back with the bill pointed upward at a sharp angle, although not 
quite perpendicular. (Bird artists who have attempted to portray 
a singing bird of this species have usually done so incorrectly.) 
The bird's head and body are not tilted upward when singing 
muted or whisper songs. 

The Swainson's Warbler sings from the ground, and from trees, 
shrubs, vines, and logs, usually below 30 feet. I have heard a bird 
singing from a perch as high as 50 feet, but singing from such a 
height is very uncharacteristic. 

Singing from the ground is usually sporadic, since it is done 
while hunting for food. The bird nearly always stops to sing when 
foraging along the ground, assuming virtually the same posture 
as when singing from a branch; sometimes it starts singing be- 
fore coming to a complete halt. After a male has spent some time 
on the ground intermittently foraging and singing, he may fly 
to the limb of a tree, where he rests, preens, or continues singing. 

During the first few days after they arrive on the breeding 
grounds, birds in the canebrakes of the Ocmulgee River floodplain 
forest sing much more often from the ground than from trees or 
shrubs. In 40 hours of observation, three of four individuals were 
observed to sing only from the ground during their first week, 
April 12-19, 1965. During April 12-15, 1966, soon after the birds 
had arrived on the breeding grounds, one male sang only from 
the ground when under observation for 10 hours. When I next 
observed this bird, on April 28, it sang also from trees. Another 
male sang 135 songs from the ground and 65 from trees when 
under observation for 90 minutes on April 15. 

When the Swainson's Warbler sings from trees, some of the 
perches most often used are dead branches well out from the 
trunk in the lower parts of the trees. The bird sings from a sta- 
tionary position when perched in a tree or shrub, as pointed out 
by Brewster (1885a, p. 73-74) : 

While singing he takes an easier posture, but rarely moves on his perch. If 
desirous of changing his position he flies from branch to branch instead of 
hopping through the twigs in the manner of most warblers. 

However, a singing bird may reverse its position on the same 
perch and resume singing while faced in the opposite direction. 

In the course of 1 hour a Charleston, W. Va., male sang from 
18 perches, once only from each of 17, and five times from one. 



68 NORTH AMERICAN FAUNA 69 

In the Dismal Swamp on June 3, 1966, a Swainson's Warbler 
shifted from perch to perch during the first half hour or more 
of the morning song. The bird started singing at 4 : 27 a.m. It sang 
from the first location for 11 minutes, from the second for 10 
minutes, from the third for 10 minutes, from the fourth for 4 
minutes, from the fifth for 1 minute, and from the sixth for 
1 minute. It began feeding and singing from the ground at 
5:15 a.m. 

Seasonal song cycle 

The song period in the breeding range lasts from 5 to 6 months, 
depending on locality, but the most vigorous singing occurs during 
April and May. Males still mated in June and July sing almost as 
frequently as earlier in the breeding season. Singing is fairly 
regular but mostly in the morning until about August; it is 
sporadic from mid-August to mid-September when birds begin to 
leave the breeding grounds. 

In floodplain forests of the Ocmulgee River in Georgia and the 
Arkansas River in Arkansas, I heard individuals singing daily 
in July and August. On August 6, 1966, during a 2-hour period 
(11 a.m. to 1 p.m.) when I was in a canebrake near Pendleton 
Ferry, Ark., a male sang 93 songs. In this same area on Septem- 
ber 7, 1968, four males sang sporadically in the morning until 
about noon. They sang complete, incomplete, and whisper songs. 
Much of their singing was instigated by Carolina Wrens, which 
are among the loudest songsters of the southern woods. 

The male sings vigorously following arrival on the breeding 
ground and until the pair bond is formed. Then, while traveling 
with and courting his mate during the prenesting period, he sings 
very little. Most of the singing is during the first 2 or 3 hours 
after daylight. After 7:30 or 8 a.m. during this period males may 
sing only half a dozen songs during the rest of the day. Such 
songs later in the day are usually for the purpose of rallying the 
mate. 

During nest building, singing may be sporadic, and often very 
little singing is done. The male may sing infrequently in the morn- 
ing while the female is working on the nest, but in the afternoon 
when nest building is at a virtual standstill the pair remains 
together and the male sings hardly at all. On the first day of nest 
building, a Dismal Swamp male sang only one cadence, of 7 
seconds, between 9 a.m. and 6 p.m. The next day he did not sing 
at all after 9 a.m. 

During incubation the male sings more often than during the 
courtship, mating, and nest-building periods. One of the functions 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 69 

of song during incubation appears to be to let the female know 
of her mate's whereabouts. I assume this, since the incubating 
female, upon leaving the nest, often goes to the male, with whom 
she feeds. 

Singing during the nestling period is sporadic, since the male 
assists in the feeding of the young ; after the young leave the nest, 
apparently only the female attends them, and the male increases 
his singing. During a 2-hour period (10:30 a.m. to 12:30 p.m.) 
when a Dismal Swamp female was attending her fledglings, the 
male sang a course about once every 10 minutes. After destruction 
of its mate's first nest, another male sang vigorously throughout 
the day and moved about the territory much more than usual; 
the female became very quiet and avoided the male, although she 
remained in the territory. 

Daily pattern 

The daily singing schedules of the Swainson's Warbler and 
other passerine woodland birds are about the same. In the Ocmul- 
gee River forest the first singing of the Swainson's Warbler and 
other woodland birds was noted on a mild, cloudy morning, April 
14, 1966. Sunrise was at 6:07 a.m. The first bird that sang was a 
Cardinal at 5 :25 a.m., followed by a Rufous-sided Towhee at 5 :32, 
a White-throated Sparrow (Zonotrichia albicollis) at 5:33, a 
Wood Thrush (Hylocichla mustelina) at 5:35, and then two 
Swainson's Warblers at 5:47. The Swainson's was the first war- 
bler to sing, followed by a Prothonotary Warbler at 5:55 a.m. and 
a Hooded Warbler at 5:57 a.m. Almost all species of woodland 
birds were singing by 6 a.m. 

In one of my study areas in the Dismal Swamp on June 3, 1966, 
the first Swainson's Warbler sang at 4:27 a.m., following a 
Cardinal, Wood Thrush, Wood Pewee (Contopus virens), Crested 
Flycatcher (Myiarchus crinitus), Hooded Warbler, and Tufted 
Titmouse (Parus bicolor), all of which began singing after 4:05 
a.m. Sunrise was at 4 :44 a.m. 

On April 14, 1966, in the Ocmulgee floodplain forest, two 
Swainson's Warblers with adjoining territories stopped singing at 
7 and 7:14 p.m. On June 2, 1966, in the Dismal Swamp, a Swain- 
son's Warbler sang until 6:45 p.m. Only the Wood Thrush, 
Cardinal, and Wood Pewee sang later in that section of the woods. 
Sunset was at about 7 :28 p.m. 

Rate of singing 

A song is sung in a course or series, that is, a period of steady 
singing for several minutes at a time. Sometimes in the early 



70 NORTH AMERICAN FAUNA 69 

morning the pause between courses is so brief that they seem to 
run for half an hour or more. Norris and Hopkins (1947, p. 8) 
noted that the average interval between songs of a male at Tifton, 
Ga., was 10.7 seconds. 

The rate of singing is usually faster at the beginning of a course 
of songs (see table 3). During the first hour of morning song on 
June 2, a Dismal Swamp male sang at a fast but gradually di- 
minishing rate of speed: nine songs per minute for the first 8 
minutes, and five or six per minute thereafter. 

The rate of singing is sometimes relatively constant over long 
periods of time. A male in the Ocmulgee floodplain forest on April 
19 sang between 40 and 46 songs (40, 42, 46, 43, 42) in each 
15-minute period from 8 to 9:15 a.m. Table 4 shows songs per 
15-minute interval by a male in the Dismal Swamp. 



Table 3. — Songs per minute in courses by a territorial male Swainson's 

Warbler 

[4:15 p.m. to 6:43 p.m., 15 June 1966, in the Dismal Swamp in Virginia. Data from 
Meanley, Wilson Bulletin, 1968, p. 75] 



Minutes in course 


Time 




Songs in each minute 


5 


4:15-4:20 


8, 
8, 
7, 
8, 
9, 
5, 
8, 
5, 
7, 
5, 


5, 
6, 
7, 
6, 
6, 
5, 
4, 
5. 
5, 
6, 


5, 
5, 
7, 
4, 
5, 
5, 
1. 

3, 

4. 


3, 2. 


5 

« .... 

13 


4:27-4:32 

4:40-4:46 
. 4:50-5:03 


2, 4. 

4, 4, 4. 

5, 5, 4, 5, 6, 6, 5, 5, 4, 1. 


12 


5:13-5:25 


4, 5. 4, 4, 4, 3. 4, 4, 2. 


5 


5:26-5:31 


6, 5. 




5:48-5:51 




2 


6:14-6:16 




S 


6:33-6:38 


4, 2. 


3 


6:40-6:43 











NATURAL HISTORY OF THE SWAINSON'S WARBLER 



71 



Table 4. — Number of songs per 15-minute interval of a territorial male 

Swainson's Warbler 

[Observation made 3 June 1966, at Dismal Swamp, Nansemond County, Va. Sunrise 
about 4:44 a.m., sunset about 7:28 p.m.; sunny most of day; first song at 4:27 a.m.; 
sang until 6:45 p.m. previous evening. Data from Meanley, Wilson Bulletin, 1968, p. 76] 



Hour beginning at — 


Songs 

15 

min. 


in 15-minute period ending at 

30 45 60 Total songs 
min. min. min. in hour 


Temperature 

in woods 

(°F.) 


4 a.m. 

Sam, 



61 


27 

33 

51 

53 

47 

23 









25 

21 

1 








84 

50 

44 

48 

35 

29 







1 

7 
12 
20 





75 

48 

47 

43 

35 











3 

31 

17 








186 

192 

194 

198 

155 

76 







1 

35 

72 

59 







1,168 


42 
47 


6 a.m. 


52 


51 


7 a.m. . ... 


54 


52 


8 a.m. 


.38 


59 




24 


61 


10 a.m 

11 a m. 







87 
67 


12 noon .. . 

1 p.m 




... 


69 

68 


2 p.m 


... 


70 


3 p.m 


.... 8 


70 


4 p.m. 


. 21 


69 


5 p.m 

6 p.m. 




... 


62 

60 


7 p.m. . 


.... 


65 


Total in day 





















Cadence of delivery 

As pointed out by Reynard (1963, p. 139), an additional fea- 
ture of bird song "unconsciously recognized but not particularly 
noticed is the cadence of delivery." Reynard denned the cadence 
of delivery of a song as — 

the average length of time from the first note of a song unit to the first note 
of the succeeding unit throughout the whole song performance. The period 
timed includes that in which the song unit is heard and the silent period 
between song units. 

I recorded cadence of delivery of three territorial males on 
May 2 in the Dismal Swamp between 7 and 8 a.m. : the deliveries 
recorded were 20, 20, and 14. The average cadence for the sample 
was 13.7 seconds. Reynard (1963, p. 141-142) lists the cadence 



72 NORTH AMERICAN FAUNA 69 

of song delivery of several other parulids as follows: Yellow 
Warbler (Dendroica petechia), 11.2 seconds; Prairie Warbler, 
12.9 seconds; Ovenbird, 21.2 seconds; and Hooded Warbler, 9.8 
seconds. 

Some of the factors that influence the rate of singing are the 
stage of the reproductive cycle, time of day, and degree of ex- 
citement. During the nest-building period one male Swainson's 
Warbler had an extremely rapid cadence of 4 seconds early in 
the morning (at 6, 6:30, and 6:35 a.m.). He was signaling his 
mate, which at the time was building the nest. The course, or 
series, was short in each case, containing only four to six songs. 
On each of the three occasions, the female discontinued nest 
building and flew to her mate, a distance of about 100 feet. 

Comparison with associates 

On hot June days in the Dismal Swamp, I found the Swainson's 
Warbler to be one of the most frequent singers in the woods if it 
had an active nest or fledged young in its territory. The Red-eyed 
Vireo (Vireo olivaceus) sang more continuously, but its song did 
not stand out like that of the Swainson's Warbler. In the early 
afternoon when song activity is generally at a minimum for most 
birds, the Swainson's Warbler often was the most persistent 
singer. On July 8, 1967, a Swainson's Warbler was the only 
species that I could hear singing during a driving rainstorm. 

I have to disagree generally with Brewster (1885a, p. 72) who 
says that the Swainson's Warbler is a "fitful and uncertain 
singer" and that "you may wait for hours near his retreat, even 
in early morning, or late afternoon, without hearing a note." I 
have noted such behavior in many species of birds, but it may 
result from particular conditions at the time of observation. If 
one visits a Swainson's Warbler territory daily in the early part 
of the breeding season before pairing, it will soon be observed 
that this warbler sings as frequently as most of the other wood- 
land birds. Frequency of singing, as pointed out above, depends 
on the stage of the breeding cycle, the time of day, and the 
meteorological conditions, among other factors. Between the for- 
mation of the pair bond and nesting, they sing very little. 

ALARM OR CALL NOTE 

Next to the primary advertising song, the chip or tchip note, 
given by both sexes, is the best known vocalization of the Swain- 
son's Warbler. The chip note is sharper than the similar note of 
the Kentucky Warbler, an associate in much of the Swainson's 
Warbler breeding range. To me, the Swainson's Warbler chip is 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 73 

most like the chip of the first or last note of the song of the White- 
eyed Vireo. The two species occur together in the Coastal Plain 
Province, and I often have been fooled by the Vireo. However, it 
is not long before the Vireo reveals its identity as it follows through 
with the rest of the song or starts singing after giving the sharp 
chip note. Brooks and Legg (1942, p. 83) thought the Swainson's 
Warbler chip similar to that of the Mourning Warbler. 

The chip call is used during intraspecific territorial strife, 
when alarmed by such nest robbers as snakes, Blue Jays (Cy- 
anocitta cristata), and Common Grackles, and as a call-note for 
members of a pair. 

A variation of the chip note is used by the female during the 
mating period (see section on Courtship and Mating). In this 
case the notes may be softer and more musical, and they are run 
together, almost forming a chatterlike song. 

Another vocalization uttered by both sexes resembles the zeep 
note of various species of warblers during fall migration. I have 
heard Swainson's Warbler give this note in September when still 
on the breeding territory. On April 28 in the Dismal Swamp, 3 
days before nest building, I heard a female utter a soft zeep each 
time her mate sang. The note was so weak and the male so far 
from her that I am sure he seldom heard it. 



Feeding Behavior and Food 

FEEDING BEHAVIOR 

The Swainson's Warbler is primarily a ground feeder, but it 
sometimes searches for food a few feet above the ground in 
undergrowth. It also forages along the top sides of logs that are 
lying on the ground, and it may fly to the side of a tree trunk to 
pick off an insect that is a foot or so from the ground. Sometimes 
it reaches or hops up a few inches from the ground to take insects 
from the undersides of leaves of low-growing herbaceous plants, 
and occasionally it flies from perches in the lower parts of trees 
in pursuit of insects. Large insects are held in the end of the 
bird's bill and beaten against the ground until broken into several 
pieces. 

The Swainson's Warbler searches for food in a manner different 
from that of other ground-feeding parulids that I have observed. 
Insects are located mainly as the bird pokes its bill under leaves 
or piles of leaves, pushing them upward and searching the ground 
beneath or examining the undersides of the leaves. A leaf may 
be held up momentarily and tilted at an angle as the bird inspects 
the underside. If part of a leaf is curled, the upper and the lower 
mandible of the bird are parted to uncurl it. Sometimes, as the 
bird moves hurriedly forward lifting and shoving leaves from side 
to side, its entire body disappears beneath the leaves. Most of the 
Swainson's Warblers that I collected in the course of their food 
searching in the Ocmulgee River floodplain forest had their bills 
caked with mud. 

The bill of the Swainson's Warbler is larger and sharper pointed 
than the bills of the Ovenbird, the Louisiana Waterthrush, and 
the Kentucky Warbler, ground-feeding parulids that in the gen- 
erally level terrain of the southern floodplain forest obtain their 
food primarily from the surface of the leaf litter. The Kentucky 
Warbler works across the forest floor, often under a partial cover 
of low herbaceous vegetation such as wood-nettle, jewelweed 
(Impatiens sp.), or poison-ivy (Rhus Toxicodendron). It hops 
along, flushing insects and picking them off stems and from be- 
neath leaves of low-growing plants, and pokes its bill into piles 
of leaves or sticks. The Ovenbird (a walker) feeds similarly, but 
more in the open, as does the Louisiana Waterthrush (also a 

74 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 75 

walker) , which feeds about wet leaf litter and shallow pools and 
occasionally does some leaf-flipping, in contrast to the shoving 
aside and "plowing" of the leaf litter by the Swainson's Warbler. 
The Swainson's Warbler also obtains some food from the surface 
of the leaf litter. 

Within a breeding territory, a male usually uses several, per- 
haps half a dozen, foraging areas on the ground to which it 
consistently returns. Such areas are usually less than 50 feet 
square and free of obstructions at and just above ground level. In 
one Georgia canebrake I observed a male for 30 minutes as it 
searched for food in one of these special feeding sites measuring 
20 by 30 feet. 

When foraging in the shrub strata or undergrowth, the Swain- 
son's Warbler probes into clusters of dead leaves and the axils of 
cane plants, as is typical of the Worm-eating Warbler, a species 
which closely resembles the Swainson's Warbler in size and plu- 
mage and often occurs in the same place. 

Bill wiping 

After feeding, a Swainson's Warbler mounts a limb and, before 
preening, spends a number of seconds wiping its bill. Bill wiping 
presumably is done to remove caterpillar hairs or other insect 
parts and pieces of dirt. The Swainson's Warbler has a good rea- 
son to spend more time wiping its bill than most other parulids 
because of its continuous probing beneath the leaf mantle in moist 
or wet silty soil. 

FOOD 

A total of 11 Swainson's Warbler stomachs have been examined 
by biologists of the U. S. Department of the Interior. All were 
from birds collected in Alabama and Georgia canebrakes. These 
examinations indicate that the Swainson's Warbler is totally in- 
sectivorous. Among favorite food items typically occurring be- 
neath the leaf mantle are crickets (Gryllidae), ground beetles 
(Carabidae), ants (Formicidae), and spiders (Arachnidae). 

Caterpillars (Lepidoptera) occurred in five of six stomachs 
collected in May and June in Alabama and were the most im- 
portant by volume in four; ground beetles were the principal food 
item in one; and hymenopterous insects (probably ants) were 
most important in one. Spiders occurred in three of the stomachs. 

The following items, in order of volume, occurred in stomachs 
of two birds taken at Macon, Ga., in May : ground beetles, cater- 
pillars, stinkbugs, (Pentatomidae), homopterous insects (Homop- 
tera), silken fungus beetles (Nitidulidae), and beetle larvae. 



76 NORTH AMERICAN FAJJNA 69 

Crickets formed 43 and 40 percent by volume of the stomach 
contents of two birds collected near Augusta, Ga., in September ; 
other major items in the two stomachs were Acrydiinae (grass- 
hoppers), ichneumids, ants, and spiders. A stomach taken at 
Augusta in August contained the following items: 13 insect or 
spider eggs and the mass of silky material covering them, 16 
ants, two ground beetles, three unidentified beetles, seven unde- 
termined insect larvae, one caterpillar, one millipede (Diplopida), 
one stinkbug, one rove beetle (Staphylinidae), one darkling beetle 
(Tenebrionidae), and one beetle larva. 

Near Cienfuegos in Cuba, Eaton (1953, p. 172) collected several 
Swainson's Warbler stomachs that contained the bones of small 
lizards (Iguanidae). He also found such bones in the stomachs of 
Worm-eating Warblers and Ovenbirds. 



Miscellaneous Notes on Behavior 

GROUND LOCOMOTION 

The gait of the Swainson's Warbler is different from that of 
any other ground-feeding parulid. In searching for food, usually 
in dry leaf litter, its gait is described by Brewster (1885a, p. 74) 
as "distinctly a walk." Norris (1963, p. 47) also observed that it 
walked, and that its "gait was rather rapid and jerky, suggestive 
of that of the starling." He further stated that the Swainson's 
Warbler may hop "when traversing leaf litter." After 25 years 
of observing this species for many hours each spring, I would 
say that it hops some of the time, though mostly it moves in a 
rather rapid step that is a sort of a cross between a walk and a 
hop, suggesting a canter. 

In searching for food on the ground it moves along hurriedly, 
often turning from side to side, and sometimes making a complete 
turnabout (180°) in a single hop or jump. 

Another characteristic peculiar to this species while foraging 
on the ground is the quivering or tremulous movement of the 
posterior part of its body which sometimes occurs. This is not 
just a tail movement, but a part of the lower trunk of the body 
also is involved. I have observed this movement in both sexes. 

PREENING 

"This species often sits and engages in preening and scratch- 
ing — apparently more so than does any other warbler of my 
acquaintance." So writes Norris (1963, p. 47), a Georgia orni- 
thologist who knows this warbler well. I once observed a male 
preening continuously for 7 minutes. They seem to do a lot of 
preening in the center of the breast ; this behavior must be related 
to the method of foraging, wherein the breast constantly is coming 
in contact with leaves and soil. 

HEAD SCRATCHING 

Ficken and Ficken (1968, p. 136) have suggested that the 
"head scratching method may prove a valuable addition to the 
set of complex characters that can be used in defining genera." 
In the course of a series of observations of Swainson's Warblers 
in the Dismal Swamp in Virginia, I observed head scratching in 

77 



78 NORTH AMERICAN FAUNA 69 

three individuals : four times in one, three times in another, and 
once in a third. The three birds used the direct method, bringing 
the foot forward and under the wing. Ficken and Ficken (1968, 
p. 136) indicate that some Vermivora scratch directly and others 
indirectly and that all species of Dendroica observed in the wild 
scratched indirectly. 

TAIL SPREADING 

Tail spreading or fanning by a male may occur following terri- 
torial boundary disputes with another male. This is usually done 
by a male that invades another's territory and is driven out. I 
once saw a male on territory fanning its tail while being pursued 
slowly by a Redstart that had young in the territory. 



Factors Affecting the Population 

The Swainson's Warbler is the least abundant of southern war- 
blers, except for Bachman's Warbler. There are several reasons 
why the Swainson's Warbler is not more successful. From my 
observations it would appear that it has a lower nesting success 
than most other species of warblers. In a total of 16 nests of 
which I am reasonably sure that my presence had nothing to do 
with desertion, only three were successful. Some of these were 
second attempts; others were initial attempts, in which case the 
birds may have been successful on the second try. At three of the 
nests, cowbirds removed all of the Swainson's Warbler eggs. A 
mouse expropriated another nest during the laying period, and 
two nests were abandoned with clutches intact. 

Some of the reasons for its low nesting success may be the 
vulnerability of the large, bulky nest that is poorly concealed, is 
located close to the ground, and contains white eggs. Other 
species of warblers nesting in the same breeding range have 
better-concealed nests, most of which are much smaller, and all 
of which contain speckled eggs except the very rare Bachman's 
Warbler, which also has white eggs. Furthermore, most Swain- 
son's Warbler nests are lined with dark material, so that the 
white eggs stand out against the dark background. 

In the Dismal Swamp, I found that whenever a Common Grackle 
or a Blue Jay had a nest in or near a Swainson's Warbler nesting 
territory, the warbler's nest was almost always robbed. However, 
since the Grackle and Jay begin nesting before the Swainson's 
Warbler, and their nesting seasons overlap the first nesting at- 
tempt of these warblers, a second attempt can be made after the 
two nest plunderers have completed nesting and left the area. 

Since the Swainson's Warbler places its not-too-well-hidden 
nest close to the ground, it is well within the "cruising" range of 
various snakes and mammals. C. E. Collier, Jr., (1941, p. 28) 
discovered a milk snake (Lampropeltis triangulum) in the act of 
robbing a Swainson's Warbler nest, near Clarksville, Tenn. The 
snake had one of the warbler's eggs in its mouth at the time. 

Cowbird parasitism is becoming a more important limiting 
factor. Friedmann (1929, p. 150) and Mayfield (1965, p. 13-18) 
believe that the cowbird originated in the prairies and plains of 
the West, and only in the last 100 years or so invaded the eastern 
forest. As late as 1950 most of the southeastern Coastal Plain 

79 



80 NORTH AMERICAN FAUNA 69 

was outside the breeding range of the cowbird, but it is gradually 
extending its breeding range into that area (Webb and Wetherbee 
1960, p. 83-87). The cowbird is a common breeding bird through- 
out the lower Mississippi Valley and Appalachian mountains 
nesting range of the Swainson's Warbler. 

Since one of the choice nesting sites of the Swainson's Warbler 
in the Coastal Plain is the river floodplain forest, production is 
markedly limited when such areas become inundated during the 
nesting season. In the Ocmulgee River floodplain of central 
Georgia, virtually all of the Swainson's Warblers nest within 
half a mile of the river. This is where the canebrakes are located. 
Some of the birds nest right up to the river bank. I have seen 
some Swainson's Warbler territories that were under 12 feet of 
water. Three out of 10 years that I worked in this area the nesting 
ground was flooded during May when the Swainson's Warbler 
was nesting. 

Calhoun (1941, p. 306) found a similar situation in the Hatchie 
River bottoms in Hardeman County, Tenn. He made the following 
statement about these conditions : 

If the Swainson's warbler nests in this same type of region, it would be 
exceedingly difficult to study its nesting habits because such areas are subject 
to flooding in the spring and early summer. 

In the Coastal Plain part of its range the Swainson's Warbler 
would probably have a difficult time maintaining its present popu- 
lation level, not only because of low nesting success, but also 
because of its narrow habitat requirements. Canebrakes, prime 
habitat of this species, have disappeared faster than any other 
bottomland plant community. Habitat has disappeared faster in 
the lower Mississippi Valley than elsewhere in the range. Very 
early, rich bottomlands of the lower Mississippi Valley were 
stripped of their valuable hardwood timber and then cleared and 
drained for the agricultural use of their highly productive soils. 
Habitat in the Great Dismal Swamp and some other South 
Atlantic lowlands has contracted because the deep shade required 
by this species disappeared with the harvesting of the mature 
forest. The cut-over areas were drained and reforested with pine. 

It is possible that the Swainson's Warbler can adapt to so- 
called marginal Coastal Plain habitat better than is suspected. 
Some occur there, but these usually are bachelor males. But if 
the Swainson's Warbler ever has to make a last stand it may well 
be in the Southern Appalachians, where many of them occur in 
national forests and national parks or in areas unsuitable for 
agricultural production. 



Summary 

The Swainson's Warbler is one of the least known of southern 
birds. Studies of its life history and ecology were made by the 
author principally in canebrakes along the Ocmulgee River a few 
miles south of Macon, Ga., and near Pendleton Ferry, Ark., in 
deciduous thickets in the Dismal Swamp, Va., in scrub palmetto in 
Monkey John Swamp, S.C. ; and in mountain cove hardwoods near 
Charleston, W. Va. 

The Swainson's Warbler was described by Audubon from 
specimens collected. by John Bachman on the banks of the Edisto 
River in South Carolina in 1832 or 1833. John Abbot, a Georgia 
naturalist, collected a specimen some 25 years earlier but made 
no record of the event. However, he made an identifiable portrait 
of the bird. His illustrations of birds were discovered many years 
later in several museums. 

The Swainson's Warbler spends nearly 6 months in the United 
States. During this period (summer half of year) it is primarily 
associated with the river floodplain forests and swamps of the 
South Atlantic and Gulf Coastal Plain and the rich moist woods 
of the Mixed Mesophytic forest of the Southern Appalachians. 

The main wintering ground is the Caribbean archipelago in the 
general latitude of 20° N., especially the islands of Jamaica and 
Cuba; individuals also winter in the Yucatan Peninsula and 
British Honduras. 

Some migrants apparently fly across the Gulf, some around it. 
First spring migrants reach the southern coast of the United 
States usually by the last half of March or the first week in April. 
Most birds are on the breeding grounds by April 15, but some 
arrive by the first week in April. In the fall most have departed 
from the breeding grounds by September 15. 

The optimum habitat is rich damp woods with deep shade, 
moderately dense undergrowth, and relatively dry ground. Giant 
cane, scrub palmetto, and sweet pepperbush are the most im- 
portant plants of Coastal Plain breeeding grounds ; rhododendron 
and cove hardwood shrubs are important in the mountains. 

In April 1968, I counted 19 territorial males along a 2-mile 
transect through canebrakes near Macon, Ga. I found eight terri- 
torial males along a 0.5-mile transect in the Dismal Swamp in 

81 



82 NORTH AMERICAN FAUNA 69 

Virginia, April 20, 1958. Brooks and Legg counted 10 or 11 sing- 
ing males along 1.5 miles of Franzy Creek in Nicholas County, 
W. Va. 

The Swainson's Warbler is 5 to 5V& inches in length, and during 
the breeding season weighs about 15 grams. Breeding birds of 
the Southern Appalachians usually have whiter underparts than 
Coastal Plains birds. 

The Swainson's Warbler is one of the last of the southern 
warblers to arrive on the breeding grounds, but is earlier than 
most northern transient members of the family. One banded male 
returned to the same territory in Maryland for five consecutive 
breeding seasons. 

Nine territories ranged in size from 0.3 to 4.8 acres. The size 
and shape of a territory varies during different phases of the 
breeding cycle. 

Hostile encounters between neighboring males usually take 
place along territorial boundaries. Paired males usually initiate 
border encounters with unpaired males. A display is sometimes 
performed by an aggressive male after it is driven back into its 
territory. 

During courtship and mating the male sings very little. Fre- 
quently he flies to the female, who usually is foraging on the 
ground, and either pecks at her rump or pounces on her. Copula- 
tion sometimes takes place during pouncing. 

First nests usually are built by the first week in May. Although 
other investigators reported finding nests outside the defended 
territory, all nests that I found were within the territory. The 
large bulky nest of this species is usually placed 2 to 6 feet above 
the ground. It is built by the female from materials gathered 
close to the nest site ; she takes 2 or 3 days to complete it. 

Three and occasionally four white eggs are laid. At a Dismal 
Swamp nest the incubation period was 13 days. The cowbird 
parasitizes nests in some parts of the breeding range. 

During incubation two females spent 54 and 78 percent of day- 
light time on the nest. Both sexes feed young and clean the nest. 
Young remain in the nest 10 to 12 days. Fledglings of one brood 
were attended only by the female. 

The song of the Swainson's Warbler is loud and ringing and of 
marked musical quality. It consists of three or four high intro- 
ductory notes, all separated, followed by a phrase of four or five 
syllables uttered rapidly, and slurred. Songs are delivered at a 
rate of about 8 or 9 per minute for the first few minutes of morn- 
ing song, then decrease to 5 or 6 per minute for most of the 



NATURAL HISTORY OF THE SWAINSON'S WARBLER 83 

morning. Songs are given in courses or series. The rate of singing 
is usually faster at the beginning of a course. The number of 
songs sung by a territorial male in 1 day, June 3, in the Dismal 
Swamp was 1,168. It produced 186 songs the first hour and sang 
at a fairly constant rate from 5 to 8 a.m., 192, 194, and 198 songs 
per hour. 

Muted or whisper songs are a continuous chatter that may go 
on for as long as 3 minutes. They do not resemble the primary 
advertising song and may be given in the presence of other 
Swainson's Warblers or when alone. The alarm note is a sharp 
chip. A weaker chip is used for communicating during courtship. 

The primary advertising song is sung from the ground and 
from perches at low elevations. The whisper song is usually given 
from the ground. 

The Swainson's Warbler is primarily a ground feeder, but 
sometimes searches for food a few feet above the ground in under- 
growth. Insects, its main food, are located as the bird pokes its 
bill under leaves, pushing them upward and examining the under- 
side, and searching the ground beneath. Foods gleaned from 
beneath the leaf mantle usually are ground beetles, crickets, ants, 
and spiders. Sometimes caterpillars are taken in the course of 
foraging in the shrub strata. 

The usual gait of the Swainson's Warbler is a cross between 
a hop and a walk, suggesting a canter. The direct method is used 
in head scratching, that is, bringing the foot forward and under 
the wing. Tail spreading or fanning by a male may occur follow- 
ing a territorial boundary dispute with another male. 

The Swainson's Warbler is one of the least abundant of south- 
ern warblers. It has a low nesting success because its large bulky 
nest is poorly concealed, is located close to the ground, and con- 
tains white eggs. In parts of its range it is highly parasitized by 
the cowbird. In some Coastal Plain floodplain forests, nests are 
destroyed during floods. 



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I, Charleston, S.C. 254 p. 



90 NORTH AMERICAN FAUNA 69 

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