Geothlypis philadelphia.
Descriptions of First Plumage of Certain North Am, Bbs. Wm. Brewster.
39. Geothlypis philadelphia.
First plumage: female. Remiges, rectrices, etc., as in adult. Rest of upper parts, with wing-coverts and sides of head, dull reddish-brown, becoming almost cinnamon on the back, and tinged strongly with ashy on the pileum. Entire under parts light reddish-brown, most pronounced on the abdominal and anal regions, becoming lighter on the throat, and darker, with a strong olive suffusion, on the breast and sides. No appreciable maxillary or supra-orbital stripes. From a specimen in my collection shot at Upton, Me., August 11, 1876. This bird was very young; in fact, barely able to fly. A slight doubt exists in my mind as to its identity, for I did not actually see the parent birds feed it, though both were in the immediate vicinity and exhibited much solicitude. This specimen is separable from the corresponding stage of G. trichas by the ashy cast of the pileum and the absence of brownish on the sides.
Autumnal plumage: young male. Entire upper parts olive-green, the feathers of the pileum and nape being just tipped with this color and showing plainly the ashy underneath when disarranged. Sides of head, with broad bands extending down each side of the throat and nearly meeting across the jugulum, ash, washed with greenish-olive. Sides, with a broad connected band across anal region and breast, dull olive-green. Rest of under parts, with central areas of throat and jugulum, very clear rich yellow, intensifying into a spot of orange on the breast. In two specimens (both males) a yellow tipping of the feathers on the jugulum nearly conceals much black underneath, which becomes conspicuous when the plumage is slightly disarranged.
Autumnal plumage: young female. Similar to the male, but with a more olive cast to the green of the dorsal aspect, less ashy on head, and the spot on the breast of richer, deeper color, and broader diffusion. The young of both sexes in autumnal plumage have the upper and lower eyelids conspicuously fulvous-yellow. In one specimen (male, taken August 21), the eyelids are dirty-white. From seven specimens (two females, five males) in my collection shot at Upton, Me., August, 1874. Irrespective of generic characters, the young of G. philadelphia in autumn are at once distinguishable from those of Oporornis agilis in corresponding stages, by the total absence of ashy on the central regions of throat, jugulum, and breast. So marked is the difference that obtains in this respect that I am easily able to separate the two species, when lying side by side, at a distance of fifteen or twenty feet.
Bull. N.O.O. 3, April, 1878. p. 61-62.