IDENTIFICATION
The Tennessee warbler “Vermivora peregrine” is a medium size, 11.5 cm in length. This is a small transatlantic vagrant with a fairly plump, short-tailed parulid. In the first winter or (slightly less bright) adult female winter plumage in autumn, an un-streaked green and yellow warbler with contrasting white undertail coverts, a rather poorly defined (and not very long) yellow supercilium, and one or two faint pale wing-bars often (maybe only adults) show a tiny whitish area at tail corners.
This clearly suggests a Phylloscopus, whose name call confusingly similar to that of the Arctic Warbler. The brightness of plumage is not normal for the Arctic (the race of Arctic breeding from Kamchatka to Japan, xanthodryas, not yet recorded in the European region, is, however, very yellow below) and further differs in having clean, whitish tips compared to primaries in fresh plumage, greyer legs, and a greyer, more sharply pointed bill with a pale grayish lower mandible.
Overall, the colors are more suggestive of the Wood Warbler, but the latter is stockier and has a longer primary projection, whiter underparts from the lower breast down, brighter green fringes to wing feathers, no white tips to primaries, no pale wing bar, a blunter bill with a more pinkish lower mandible, pinkish legs, and a diverse call (but is usually silent on passage).
Compare also Green Warbler and Philadelphia Vireo. The adult female winter is very comparable to the first winter, and so similar identification problems apply but are averagely duller. Adult male winter is often whiter below and on the supercilium and grayer on the crown than adult female winter, but many are indistinguishable.
The adult male summer is markedly whiter below and on the supercilium and has crown and ear covers that are noticeably dull bluish-gray. Whereas adult female summer is alike but has yellow-tinged supercilium and ear covers, a greenish crown, and more yellow underparts. Thus, consequently, both sexes are less likely to be confused with Phylloscopus warblers.
This is a very active warbler, continuously on the move in the canopy of trees and shrubs, calling freely. In spite of being no closer to the state of Tennessee than to northern Michigan, almost six hundred miles away!
SEX/AGE
Tennessee warbler adult male summer has whitish supercilium and underparts and bluish-grey crown and ear coversts, contrasting with dull olive upperparts; adult male winter has headed more olive, less grey, and there may be a hint of yellowish in underparts.
Adult female summer is less gray on the head than male, with a stronger yellow wash to the supercilium and underparts; in winter plumage, it is much brighter overall and similar to first-winter birds. 1st-winters are very bright green and yellow (check out Identification), but are often not distinguishable in the field from the brightest adult females. The name was given by Alexander Wilson when, during their migration, he encountered a beautiful bird in Tennessee.
VOICE, SONGS, AND CALLS
Tennessee warbler given freely by migrants, a short, rasped ‘zik’ (recalling Arctic Warbler, but sharper and less metallic), and a thin ‘zeep’ (recalling a single note of Firecrest). The Tennessee Warbler song is distinctive: a fairly loud, staccato series of two-syllable notes, followed by a few higher-pitched single notes, and finally a trill:’sidit-sidit-sidits-swit-swit-swit-sit-sit-sit-sit-sit-sit’.
HABITAT
The Tennessee warbler is a vagrant in Western Europe; however, in the natural range, it breeds in coniferous and mixed woodland; on migration, it also breeds in open deciduous woodland, scrubby areas, and thickets. Normally, the cup-shaped nest is built by females on open grass stems lined with fine dry grass, porcupine quills, and decorated with moose hair.
The Tennessee warbler habitually hid in a depression on the ground under bushes or hanging grass. The place is normally on mossy hummocks in wet fields, but it builds a nest on fairly dry ground on steep hillsides.
