Life Histories of North American Wood Warblers, Part One and Part Two. Arthur Cleveland Bent
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 Yucatán 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 Tillandsia, 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 1.00. * * * 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 finished 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 fibre, 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 21⁄2 feet high. S. A. Grimes has sent us a photograph of a nest on the broad leaf of a saw palmetto (pl. 7). Albert J. Kirn (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. maximum) 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 113⁄16 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 “cinnamon-brown” 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 reddish-brown, the crown scarcely deeper-colored than the back, the wings a trifle redder; loral stripe blackish;