Male Black-throated Blue Warblers are dark blue with black throats and white undersides; while the female is largely drab olive. Both sexes have a prominent white patch at the base of their primaries. Small white patch in wing can be inconspicuous in immatures.

Black-throated Blue Warblers build their nests mid-story in trees. They feed primarily on insects and lay 3 to 5 eggs.

Length: 5 1/4 inches

Habitat: Deciduous forests; usually seen in lower or mid-level branches.

Voice: A single sharp "dit," similar to a Dark-eyed Junco.

Other Behavior: Rare fall vagrant in the west. A few birds winter in south Florida; most migrate to the West Indies. Habitat loss in both its breeding and wintering range are a threatening populations of Black-throated Blue Warblers.