Blackpoll Warbler

The Blackpoll Warbler is a small, hard-working songbird famous for undertaking one of the most physically demanding migrations of any passerine. Breeding in the high-latitude boreal forests of North America, this species undergoes a dramatic double-migration, wintering in South America's Amazon Basin. To prepare for its journeys, this tiny bird can nearly double its body weight, storing the fat required to power a non-stop, multi-day flight of several thousand miles over the Atlantic Ocean. Though abundant historically, the population has experienced steep declines in recent decades.

Identifying the Blackpoll Warbler depends heavily on the season, as its plumage changes dramatically.

Breeding Plumage

• Male: Boldly patterned with a solid, coal-black cap (the "poll") contrasted by stark white cheeks and a clean white throat. The back is gray with heavy black streaks, and the underparts are white with black streaks running down the flanks. Two conspicuous white wingbars are present.
• Female: Much more drab. The head and back are olive-green with dark streaks, and the underparts are pale yellowish to white with faint dark streaking.

Fall (Non-breeding) Plumage

In autumn, adults and immatures molt into a confusing yellow-green color palette, often referred to as "confusing fall warblers."

• Both sexes show greenish-yellow heads and breasts with faint streaking on the back and flanks, white undertail coverts, and two pale wingbars.
• Key Field Mark: The most reliable way to separate a fall Blackpoll from similar species is by checking its feet and legs. Blackpolls consistently display pale, orange-yellow to pinkish soles and legs, whereas similar species like the Bay-breasted Warbler have dark gray or blackish legs.

Breeding Range

During the spring and summer breeding season, Blackpoll Warblers inhabit northern coniferous systems, dominated by spruce, fir, and tamarack. Their range extends across Alaska, much of Canada, the Great Lakes region, and high-altitude coniferous islands in New England and New York.

Overwintering and Migration

Blackpolls winter in the tropical rainforests and lowland evergreen forests of northern South America.

Their migration route is legendary. In the fall, they move east to the coast of eastern Canada and New England. Once there, they wait for favorable winds and launch directly over the Atlantic Ocean, flying non-stop for 72 to 88 hours to reach South America. In spring, they return via a more westerly, overland route across the Caribbean and up through the Mississippi and Atlantic flyways.

Feeding

Blackpoll Warblers are active, deliberate foragers. They move slowly through the outer branches of the canopy, gleaning insects, caterpillars, and spiders from the undersides of leaves and coniferous needles. During migration and winter, they also consume small berries.

Vocalizations

• Song: A rapid, mechanical, extremely high-pitched series of staccato notes on a single pitch: zi-zi-zi-zi-zi-zi-zi. It swells in the middle and tapers off, resembling the sound of a fast sewing machine. It is so high-pitched that some birders with age-related hearing loss have difficulty detecting it.
• Call: A sharp, high-pitched chip note.

Breeding and Nesting

Nests are built exclusively by the female, typically well-hidden in the dense outer branches of small spruce or fir trees, close to the ground (usually under 3 meters). The nest is a cup constructed of twigs, bark strips, lichens, and moss, lined with softer grasses, hair, and feathers.