Sub-category: Wood Warblers
The black-throated blue warbler measures 5.1 inches in length on average. The adult male has white underparts with a black throat, face and flanks. The upperparts are deep blue. The immature male is similar, but with greener upperparts. The female has olive-brown upperparts and light yellow underparts with darker wings and tail, gray crown and brown patches on the cheek. Both sexes have a thin pointed bill and small white wing patches which are not always visible. Like many other warbler species, it has colorful plumage during the spring and summer. However, outside the breeding season its plumage is drab and less distinctive. In the fall, the black-throated blue warbler can be distinguished by its small white wing patches. Juveniles have brown upperparts with a creamy supercilium and brownish spots on the throat, the breast and the belly.
Predominantly insectivorous, the Black-throated Blue Warbler supplements its diet with berries and seeds in winter. Found in mature deciduous forests or mixed coniferous-deciduous forest with a thick understory. The species is often found in hilly and mountainous regions. It builds its nests in thick shrubs, near the ground. The black-throated blue warbler requires large, unbroken forest areas for nesting.