Black throated green warbler

Black-throated Green Warbler (Birds of North Carolina: their Distribution and Abundance)
As a breeder in the state, it prefers conifers or mixed hardwood-coniferous forest — spruce-fir, spruce-hardwoods, and White Pine and hemlock mixed with hardwoods are favored in the mountains, though it does occur in pure hardwoods. In the foothills, it favors pines (and formerly hemlocks) mixed with hardwoods. Birds in the Coastal Plain are somewhat particular — they are essentially only in nonriverine forests, favoring sites where Atlantic White Cedar or cypress are mixed with hardwoods, but they may occur in pure hardwoods. Floodplain forests are avoided (for reasons that are not obvious, as cypresses are often common there), but some birds do nest along small streams.

Black-throated Green Warbler (
Active and agile, Black-throated Green Warblers primarily forage for small insects hiding in the bases of the leaves of tall trees. Breeding males sing on exposed perches where their bright head is conspicuous. In fall migration and winter, they often join mixed-species flocks with resident birds.

Black-throated Green Warbler (Audubon Guide to North American Birds)
In the east, some of the easiest warbler voices to recognize are the patterned songs of the Black-throated Green. As if to confirm the identification, the brilliantly colored male often perches out in the open to sing, perhaps on a high twig of a spruce. He actually has two song types, used in different situations: he sings zoo zee zoo zoo zee to proclaim and defend his nesting territory, and zee zee zee zoo zee in courtship or when communicating with his mate.

Singing male black-throated green warbler (Youtube video, Cornell Lab of Ornithology)

Warbler ID (Youtube video, Cornell Lab of Ornithology)
Warblers are a favorite among birders of all skill levels because they’re so rewarding. With their bright colors and globe-trotting habits, warblers add excitement to spring birding. But they often flit by quickly and can be tricky to identify. We know that it can feel overwhelming at first. Get the help you’ve been looking for with a course that gives you practice identifying all 51 warblers from across the United States and Canada.