Swainson’s Warbler

Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.

Bent Life History for the Swainson’s Warbler – the common name and sub-species reflect the nomenclature in use at the time the description was written.

“The history of our knowledge of Swainson’s Warbler,” write Brooks and Legg (1942), “is a curious one, falling into definite periods.” This bird was discovered in the spring of 1832 by the Rev. John Bachman “near the banks of the Edisto River, South Carolina.” His discovery of the bird is described as follows: “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 to me and soon shot it” (Audubon, 1841). Dr. Bachman took five specimens; then, up to the spring of 1884, Swainson’s warbler remained almost a lost species, for according to Brewster (1885a) there is no record of more than eight or nine birds being collected. Wayne, through collections and field work near Charleston, opened a productive 25-year period in the history of swainsonii, in which many valuable contributions were made by various observers. From 1910 to 1930 the name swainsonji was practically absent from the pages of current ornithological literature.

Brewster (1885a) has given us the best description of the bird’s haunts in the low country:

The particular kind of swamp to which he Is most partial Is known In local parlance as a “pine-land gall.” It Is usually a depression in the otherwise level surface, down which winds a brook, In places flowing swiftly between well defined banks, in others divided into several sluggish channels or spreading about in stagnant pools, margined by a dense growth of cane, and covered with lily leaves or other aquatic vegetation. Its course through the open pine-lands is sharply marked by a belt of hardwood trees nourished to grand proportions by the rich soil and abundant moisture. Beneath, crumbling logs cumber the ground, while an under-growth of dogwood (Cornus florida), sassafras, viburnum, etc., is interlaced and made well-nigh impenetrable by a net-work of grapevines and greenbriar. These belts: river bottoms they are in miniature: rarely exceed a few rods in width; they may extend miles in a nearly straight line.

The writer has had a long acquaintance with Swainson’s warbler in the low country of Carolina. Except during September (fall migration) the birds were almost never seen out of sight of substantial growths of cane, even when the nests were built in bushes, low trees, or vines. This has been the experience of practically all observers and, as Brooks and Legg (1942) remark, “an idee fixe among ornithologists” existed; the familiar description of habitat by Brewster (1885a) became a dictum: “Briefly, four things seem indispensible to his existence, viz., water, tangled thickets, patches of cane, and a rank growth of semi-aquatic plants.”

Hence, the ornithological world received a surprise to learn that swainsonii was a summer resident and breeder in different localities of high altitude in the Appalachian Chain. Although several observers have found the bird nesting beyond the limits of the Coastal Plain, even in Piedmont territory, as La Prade (1922) did at 1,050 feet above sea level, it was E. A. Williams (1935) who first detected it in a truly mountainous terrain. During two successive summers he found birds near Tryon, N. C., “in open woods.”

Loomis (1887) was quite prophetic when, in recording a Swainson’s warbler from Chester, S. C., “in the heart of the Piedmont Region, one hundred and fifty miles from the coast,” he wrote: “It awakens the mind to the possibility of an Up-Country habitat, yet awaiting discovery, where the true centre of abundance will finally be located.”

The efforts of Brooks and Legg (1942) have shown Swainson’s warbler to be a locally common summer resident in south-central West Virginia up to an elevation of 2,000 feet above sea level; no positive evidence of breeding has been found, but it undoubtedly does breed. In Tennessee, Wetmore (1939) has found the bird in mountainous country at 3,000 feet.

The question naturally arises, Did Swainson’s warbler always inhabit higher altitudes, or is this a recent extension of range and partial change of habitat? The answer will probably never be found; but study of changing conditions in its low country habitat for the past several decades may throw light on this interesting problem. Within the writer’s experience the canebrake areas have long been exposed to forest fires, timber cutting, overgrazing, drainage, and the construction of a hydroelectric project, as a result of which thousands of acres of timbered swampland are now under water.

Spring: The birds that winter in Jamaica enter the United States through Florida, but it is probable that those from YucatAn make a direct flight across the Gulf to the delta of the Mississippi. The earliest recorded spring arrival in the United States was on March 22, 1890, on the lower Suwanee River. The same year the species was taken at the Tortugas, March 25 to April 5 (Chapman, 1907). The earliest arrival near New Orleans, was March 30, 1905 (Kopman, 1915). Meanley (MS.) records it from central Georgia on March 31, 1944. Swainson’s warbler reaches the vicinity of Charleston, S. C., during the first week of April, the earliest being the fifth of that month.

Nesting: Nests are built in bushes, canes, masses of vines, and briers; 10 feet seems to be the maximum height from the ground, while some nests have been found as low as 2 feet. The average elevation would be around 3 feet. As many nests are built over dry ground as over water. The nest is quite bulky and loosely constructed; a typical one in situ looks like a bunch of leaves lodged in a bush or cane, as the stems point upward. The outer walls of the nest are composed of various leaves such as oak, gum, maple, tupelo, and cane; the inner walls are usually of cane, while the lining is of pine needles, black fiber of moss ( 7’iZlandsia), cypress leaves, rootlets, or grass stems. Sometimes horsehair is also present.

[AUTHOR’S NOTE: A few more notes on the nesting of Swainson’s warbler may well be added to the above general statements. Brewster’s (1885b) nests, taken by Wayne in the low country of South Carolina~, are evidently typical for that region. All four of these nests were in canes. Wayne (1886) says that the nests “are generally built in canes,~~ but he has also found them “in small bushes, and in one instance in a climbing vine, by the side of a large public road.” Brewster (1885b) gives the measurements of two of his nests; the smallest of the four measures: externally 3.50 in diameter by 3.00 in depth; internally 1.50 in diameter by 1.50 in depth; the greatest thickness of the rim or outer wall being 1.4~iJ.

The nest June 27 is very much larger, in fact quite the largest specimen that I have seen, measuring externally 5.00 in diameter by 6.00 in depth; internally 1.50 In diameter by 1.25 in depth; with the rim in places 1.75 thick. It is shaped like an inverted cone, the apex extending down nearly to the point of junction of the numerous fascicled stems which surround and support its sides. Its total bulk fully equals the average nest of our Crow Blackbird, while it is not nearly as ~nlshed a specimen of bird architecture. Indeed it would be difficult to imagine anything ruder than its outer walls,: composed of mud-soaked leaves of the sweet gum, water oak, holly, and cane, thrown together into a loose mass, bristling with rough stems, and wholly devoid of symmetry or regularity of outline. The Interior, however, lined with pine needles, moss ~bre, black rootlets, and a little horse-hair, is not less smooth and rounded than in the other specimens.

Troup D. Perry (1887), with his friend George Noble, found no less than 24 nests near Savannah, Ga., in 1887; some of these were in gall or myrtle bushes and one was in a saw palmetto 2½ feet high. S. A. Grimes has sent us a photograph of a nest on the broad leaf of a saw palmetto (p1. 7). Albert J. Kim (1918) says of the nesting sites of Swainson’s warbler in Oklahoma: “A well shaded clump of trees in the woods, such a place as would suggest itself for a Wood Thrush, yet not exactly so, with considerable ‘buck brush’ undergrowth, but no grass or weeds is selected for a nesting site. In the top of this ‘buck brush’ usually about two feet high the nest is built; about half of the nests found were close to the river bank: the Little Caney River. All but two were built in the brushy undergrowth. These two were fastened to briers and slender brush and were higher up, 3.5 and 4 feet.”

F. M. Jones wrote to Brooks and Legg (1942) of a nest found in southwestern Virginia: “This nest was in a very dense growth of rhododendron bushes close to a stream of water where the sunlight never penetrated. It was 5 ft. 6 in. up, built in the forks of a slender beech limb which grew across the top of a rhododendron bush (R. macvim’um) and partly supported by the top of the rhododendron. * * * The outside of the nest measured 7 in. wide by 5 in. deep and the inside 2 in. wide by 113A6 in. deep.”

It is evident, from the above and other similar accounts that, at higher elevations northward and westward, Swainson’s warbler nests in bushes and vines where there are no canes to be found.]

Eggs: Swainson’s warbler usually lays three eggs; sets of four are rare and of five very rare. Although there are records of nests containing two incubated eggs or two young birds, these probably represent incomplete sets or cases where an egg or a nestling has been destroyed. Eggs are quite globular, the two ends sometimes scarcely distinguishable; the shell is thick and has a distinct polish; the ground color is white with a bluish tinge; however, a set of three eggs in the writer’s collection had a faint greenish tinge, while several observers describe sets of pale pink or buffy white.

Rarely, spotted eggs are found. Wayne (1910) says: “Spotted eggs are, however, very rare and I have found only four or five nests containing them.” The only spotted egg the writer has found is in the set referred to above; of these, two are immaculate, while the third is “faintly though distinctly speckled around the larger end with reddish brown” (Dingle, 1926).

Brewster (1885b) describes a set collected by the late Arthur T. Wayne: “One is perfectly plain; another * * * has two or three minute specks which may be genuine shell markings; while the third is unmistakably spotted and blotched with pale lilac. Over most of the surface these markings are fine, faint, and sparsely distributed, but about the larger end they become coarser, thicker, and deeper colored, forming a well-defined ring or wreath.”

Burleigh (1923) writes: “Unlike all the descriptions I had read, and the few eggs I had seen, these were light pink in ground color and dotted distinctly over the entire surface with light brown spots, this almost forming a wreath at the larger end of one egg.” These eggs were found near Augusta, Ga., and the parent was secured.

Wayne (1910) was of the opinion that two broods are raised in a season.

[AUTHOR’S NOTE: The measurements of 50 eggs average 19.5 by 15.0 millimeters; the eggs showing the four extremes measure 21.6 by 14.2, 20.8 by 16.0, 18.0 by 14.1, and 19.5 by 13.5 millimeters (Harris).]

Plumages: [AUTHOR’s NOTE: Ridgway (1902) describes the juvenal plumage of Swainson’s warbler as follows: “Head, neck, back, rump, upper tail-coverts, chest, sides, and flanks plain brown (varying from broccoli to bister) ; rest of under parts whitish or dull pale yellowish, more or less clouded with brown; middle and greater wing-coverts indistinctly tipped with cinnamon-brown; otherwise like adults, but no trace of lighter superciliary nor darker postocular stripes.” Specimens that I have seen in this plumage are more nearly “cinnamonbrown” than the colors named above on the back and wing coverts, and the latter show very little evidence of cinnamon tips.]

The postjuvenal molt, which evidently includes only the contour plumage and the wing coverts, occurs early in the summer; I have seen young birds beginning to acquire the first winter plumage as early as June 12, and others that had nearly completed the molt on July 20; these birds were not yet fully grown. Wayne (1910) writes: “I have taken young birds which were as large as the adults and which were acquiring their autumnal plumage as early as June 2, but it must be borne in mind that the season in which these young were taken (1906) was exceptionally advanced.”

Brewster (1885a) describes the young bird in its fall plumage as follows: “Entire upper parts rich olive strongly tinged with reddishbrown, the crown scarcely deeper-colored than the back, the wings a trifle redder; loral stripe blackish; superciliary stripe tinged with yellow; under parts strongly yellowish, otherwise like the adult.”

The nuptial plumage is apparently assumed by wear and fading, the reddish-brown and yellowish colors becoming much duller. There are no specimens available of either young or adult birds that indicate a prenuptial molt.

The postnuptial molt seems to occur mainly in August, but perhaps earlier, and is evidently complete; I have seen birds in full, fresh autumn plumage as early as August 28. This fresh plumage is similar to the spring plumage, but the crown and back are nearly uniform brown, the crown is darker than in spring, the back is browner than in spring, and the breast and flanks are more or less clouded with grayish.

Food: IHowell (1924) says that “four stomachs of this bird from Alabama contained remains of caterpillars, spiders, and Ilymenoptera (ants, bees, etc.).”

Brewster (1885a) considered the principal food to be small coleopterous insects, “as well as some small green worms that are found on water plants, such as the pond lily (Nymphaea odorata) and the Nelumbium (Cyamua flavicomus).

Behavior: Swainson’s warbler is an unsuspicious bird and can be easily observed in its haunts where the vegetation is not too dense and tangled and the tree canopy overhead partially open. The neutral color of. the bird is often apt to conceal him in the shadowy undergrowth. Singing males usually remain on the same perch during their periods of song, apparently disinclined to move. He often sings from the ground during insect hunting; Meanley (MS.) says: “It was so wrapped up in its song as to be absolutely unconcerned; it sang at my very feet with its head thrown back, its beak pointing perpendicularly toward the sky, pouring forth its resounding melody in the best of warbler fashion.”

The female is a close sitter, and the observer has usually to touch her before she leaves the nest. Grimes (1936) writes: “This bird would not leave her eggs until pushed off, and when I held my hand over the nest she straddled my fingers in trying to get back onto it. * * * When I did drive her away from the nest she fluttered along on the ground in the manner of a crippled bird, her actions manifestly intended to induce me to follow. This bird certainly was not badly frightened, for within a few minutes she was back on her nest, accepting deerflies from my fingers and swallowing them with apparent relish.”

Brewster (1885a) gives an admirable portrayal:

His gait is distinctly a walk, his motions gliding and graceful. Upon alighting In the branches, after being flushed from the ground, he assumes a statuesque attitude, like that of a startled Thrush. 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 bopping through the twigs in the manner of most Warbiers. Under the influence of excitement or jealousy he sometimes jets his tail, droops his wings, and raises the feathers of the crown In a loose crest, but the tall is never jerked like that of a Geothlypi8, or wagged Like that of a Siures. On the contrary, his movements are ali deliberate and composed, his disposition sedentary and phlegmatic.

Voice: 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 hoooded warbler and the Louisiana waterthrush. Close up, however, the appealing quality, lacking in the other two, impresses the listener strongly. The song has, in the majority of individuals, a highly ventriloquial effect, but the writer has listened to birds whose notes did not in the slightest degree possess this quality.

The song varies in length and number of notes but can be separated into two distinct parts; the first few notes are uttered rather slowly, the last ones more rapidly and on a descending scale. The second part closely follows the first, with no apparent separation. Brooks and Legg (1942) write: “It might be translated as whee, whee, whee, whip-poor-will, the first two (or three) introductory notes on an even pitch, the last whee a half-tone lower, and the slurred phrase with will separated into two syllables, and accented on the whip and on the wi-part of the will. The last phrase sounded at times remarkably like one of the songs of the ‘White-eyed Vireo.”

When the singer begins his performance, the bill is pointed directly up, and he seems entirely unconscious of anything but his own musical efforts. “During his intervals of silence,” says N. C. Brown (1878), “he remains motionless, with plumage ruffled, as if completely lost in musical reverie.” Brewster (1885a) adds:

It is very loud, very rich, very beautiful, while it has an Indescribably tender quality that thrills the senses after the sound has ceased. * * * Although a rarely fervent and ecstatic songster, our litle friend Is also a fitful and nncertam one. You may wait for hours near his retreat, even in early morning, or late afternoon, without hearing a note. But when the Inspiration comes he floods the woods with music, one song often following another so quickly that there Is scarce a pause for breath between. In this manner I have known him to sing for fully twenty minutes, although ordinarily the entire performance occupies less than half that time. Such outbursts may occur at almost any hour, even at noontide, and I have heard them in the gloomiest weather, when the woods were shrouded In mist and rain.

Several times the writer has seen males when the inspiration had not quite come to them; the bird would throw back its head but utter only one or two opening notes of his song.

The call note is a chip, which Brewster calls “a soft tchip indistinguishable from that of Parula americana.” But Murray (1935) writes that it is “more throaty and full-bodied than that of most Warbiers.” Brooks and Legg (1942) describe it as “clear, penetrating chirps, having (to our ears) much the same quality as do the chirps of the Mourning Warbler. They are not quite so loud, but have a more ringing quality than those of the Hooded Warbler.”

Field marks: [AUTHOR’S NOTE: Swainson’s warbler is a plainly colored bird, with no conspicuous field marks. It is brownish olive above and whitish below, with no white in either wings or tail; there is a whitish line over the eye and a dusky streak through it; but the bill is long and sharply pointed.]

DISTRIBUTION
Range: Southeastern United States to southern Mexico.

Breeding range: Until about 1935 Swainson’s warbler was considered to be confined in summer to the southern canebrakes and coastal marshes. It is now known to breed north to extreme southern Illinois, probably (seen in breeding season to Olive Branch, Duquoin, and Mount Carmel) ; southeastern Kentucky (Big Black Mountain) ; central to northern West Virginia (Charleston, Mount Lookout, Sutton, and Buzzard Rocks, Monongalia County); and southeastern Maryland (Pocomoke River Swamp). East to eastern Maryland (Pocomoke River Swamp) ; eastern Virginia (Warwick County and Dismal Swamp); eastern North Carolina (New Bern, Lake Ellis, and Red Springs); eastern South Carolina (Summerton, Charleston, and (Yemassee); eastern Georgia (Savannah and Okefinokee Swamp); and northeastern Florida (Jacksonville). South to northern Florida (Jacksonville, Oldtown, Whitfield, and Pensacola) and southern Louisiana (Mandeville, New Orleans, and Baton Rouge). West to eastern Louisiana (Baton Rouge, Bayou Sara, and Jena); central Arkansas (Camden and Conway); extreme northeastern Oklahoma (Copan) ; and central Missouri (Concordia).

Within this large breeding area are two almost discontinuous breeding ranges: the coastal and swamp range long considered the only home of the species; and the more recently discovered mountain home along the slopes of the Allegheny Mountains from northern West Virginia nearly to the Georgia line where it has been found to an altitude of nearly 3,000 feet.

Winter range: The winter home of the Swainson’s warbler is very imperfectly known from a dozen or more specimens, most of which are from Jamaica where it has been listed as a rare winter resident. There are records also from the Swan Islands (March 1); Santa Lucia, Quintana Roo; Pacaytain, Campeche; and the city of Veracruz. Two specimens have been taken near Habana, Cuba; one on September 25, the other in April; and one near Guant~namo on January 18, 1914.

Migration: Dates of spring departure are: Jamaica, April 8. Cuba: Habana, April 14.

Early dates of spring arrival are: Florida: St. Petersburg, March 25. Alabama: Autaugaville, April 3. Georgia: Savannah, March 25. South Carolina, April 1. Louisiana: New Orleans, March 30. Mississippi: Biloxi, March 31. Tennessee: Memphis, April 20. Texas: Point Bolivar, April 17.

Late dates of fall departure are: Texas: Kemah, September 27. Tennessee: Sulphur Springs, September 9. Mississippi: Gulf port, October 6. South Carolina: Charleston, October 10. Georgia: Savannah, October 18. Alabama: Greensboro, September 6. Florida: Pensacola, October 2; Sombrero Key (4 struck lighthouse November 10).

Dates of fall arrival are: Tamaulipas: Matamoros, August 29. Jamaica, October 1.

Casual records: A specimen was recorded near Corsicana, Tex., on August 24, 1880; another was collected at Kearney, Nebr., on April 9, 1905; and one near Holly, Prowers County, Cob., on May 12, 1913.

Egg dates: Florida: 3 records, May 7. Georgia: 35 records, May 4 to July 13; 19 records, May 29 to June 17, indicating the height of the season. South Carolina: 28 records, May 2 to June 30; 14 records. May 12 to June 12 (Harris).