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. 0 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
0 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
' \v L •' "
»<!>
i-:f
■ ** Jfl|
nj'i'-~
&"■
A
d
Rk ■ WS !^fi?F\iS
I
/,i
VA1
fc^
fa
^|
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^BS*«£^
vd it
.#1 L i
\
2^T ('
. Hi
^i
^
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,"
S-
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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,
0
61
27
33
51
53
47
23
0
0
0
0
25
21
1
0
0
0
84
50
44
48
35
29
0
0
0
1
7
12
20
0
0
0
75
48
47
43
35
0
0
0
0
0
3
31
17
0
0
0
186
192
194
198
155
76
0
0
0
1
35
72
59
0
0
0
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.
0
0
87
67
12 noon .. .
1 p.m
0
... 0
69
68
2 p.m
... 0
70
3 p.m
.... 8
70
4 p.m.
. 21
69
5 p.m
6 p.m.
0
... 0
62
60
7 p.m. .
.... 0
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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1935. Swainson's warbler in the North Carolina mountains. Auk, vol. 52,
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