Blackpoll Warbler

The blackpoll warbler is a fairly small bird which attains the weight of a ballpoint pen. However, it is one of the larger of the diverse genus Setophaga (formerly Dendroica). In the species, body length can vary from 12.5 to 15 cm (4.9 to 5.9 in) and wingspan can range from 20 to 25 cm (7.9 to 9.8 in). Body mass can vary from 9.7 to 21 g (0.34 to 0.74 oz), with an average bird anywhere between 12 and 15 g (0.42 and 0.53 oz). Among standard measurements, the wing chord is 6.6 to 8 cm (2.6 to 3.1 in), the tail is 4.5 to 5.4 cm (1.8 to 2.1 in), the bill is 0.8 to 1.2 cm (0.31 to 0.47 in) and the tarsus is 1.8 to 2 cm (0.71 to 0.79 in). The summer male blackpoll warblers have dark-streaked brown backs, white faces, and black crowns. Their underparts are white with black streaks, and they display two white wing bars. The adult females essentially resemble washed-out versions of the summer males, and in particular, the females lack the strong head patterns, and their crowns and faces are shades of gray. Another outstanding physical characteristic of the species is the bright orangish-pink legs. Non-breeding birds of this species have greenish heads, dark-streaked greenish upperparts, and yellowish breasts, with the yellow extending to the belly in young birds. Their wing bars are always present. …

In the southern portion of their breeding range, blackpoll warblers can be found on the higher elevations of mountains in woodland or brushy areas. They also spend their summers on the wooded coastal islands of Maine and the Maritime Provinces. Farther north, they have been reported throughout the boreal coniferous forest. Blackpolls breed nearer to the tundra than any other warbler.

Although fairly large for a warbler, blackpoll warblers are fairly easy to miss because of their relatively inactive foraging style and tendency to perch in dense foliage near the canopy of the trees. They are more often heard than seen, though their song is one of the highest-pitched known. Their songs are simple repetitions of high tsi notes. Their calls are thin sits.

Foraging and diet. The blackpoll has a deliberate feeding style with occasional flitting, hovering, and hawking around branches. They are primarily insectivorous. The species appears to be quite a generalist, preying on a great diversity of adult and larval insects and spiders. Documented insect prey for the species includes lice, locusts, cankerworms, mosquitoes, webworms, ants, termites, gnats, aphids, and sawflies. It has been suggested that this species may be a spruce budworm specialist, but there is no obvious connection between the population trends of the two species. The blackpoll will opt for berries during migration and in winter. They often forage high in trees, and sometimes catch insects while in flight.

Breeding. Their breeding habitats are coniferous woodlands, especially those in which spruce trees grow. The bird's breeding ranges extend to the taiga. Blackpoll warblers commonly nest in a relatively low site of a conifer. They lay 3–5 eggs in a cup-shaped nest, rarely up to 9. …