Setophaga caerulescens
Order Passeriformes
Family Parulidae
♂ Adult male.— Upper parts grayish-blue; a white patch in the wing; throat, and sides of head, sides of breast, and belly black; rest of breast and belly white.
♀ Adult female.— Upper parts brownish or grayish, tinged with green in strong light; line over eye dull yellowish-white; white wing-patch smaller than in male; under parts dingy yellowish.
♂ Immature male.— Similar to adult male, but upper parts tinged with olive-green, the black somewhat veiled with white.
♀ Immature female.- Similar to adult female.
Nest, in a low bush or sapling, often in laurel, hemlock, or yew, two feet or less from the ground.
Eggs, white, spotted with brown, chiefly at the larger end.
The Black-throated Blue Warbler is a common summer resident of northern New York and New England from Berkshire County, Mass., northward, and a rather common migrant through southern New England and the lower Hudson Valley, passing north in May, and returning in September and early October. It is less common as a migrant in eastern Massachusetts than in western Massachusetts or in the Hudson Valley. In summer it frequents, in the southern part of its range, cool woods of deciduous trees, beech, maple, and birch, where its drawling notes are as characteristic as those of the Black and Yellow Warbler [Magnolia Warbler] in the spruces. The song varies somewhat in form and in length: a common form consists of three rather pure notes with a downward inflection, followed by a fourth, hoarse note with rising inflection, whee-a whee-a whee-a whee-ee; another common form consists of one short introductory note and two upward hoarse notes, the whole given rapidly. The hoarse drawling character of the last notes will always serve to identify the song. The alarm-note is a rather heavy chuck.
The male is unmistakable; the female and young are rather puzzling birds, unless one can make out the small white spot on the wing, and the whitish line over the eye
Hoffmann – A Guide to the Birds of New England and Eastern New York (1904)