The Blackpoll Warbler occupies an extensive breeding range across the northern coniferous forests of Alaska and Canada, in the transition zone between taiga and tundra, and in subalpine forests and coastal spruce-fir forests of eastern North America. In some areas of its breeding grounds, it is often one of the commonest warblers present, reaching densities of up to 4 pairs per hectare.
Largely because of the remoteness of both its breeding and wintering ranges, most aspects of this species' biology have not been extensively studied, particularly in the heart of its range. The only detailed information on breeding biology comes from Kent Island, New Brunswick (Eliason 1986a, 1986b). This population showed high levels of polygyny for a warbler; site fidelity, coupled with differential returns of age and sex classes, may explain this pattern.
The only other aspect of the species' breeding biology that has received at least minimal study is habitat use (Morse 1979, Sabo 1980), and again this research was concentrated in the extreme eastern portion of the range. The frequency range of the male's song is among the highest known among birds, but detailed analysis of Blackpoll vocalizations has never been done.
Studies of fall migration route in this species have been extensive. Blackpoll Warblers undertake the longest migration of any warbler, with some individuals traveling over 8,000 km from Alaska to Brazil (Williams et al. 1977, Nisbet et al. 1995).
Part of the fall migratory route is over the Atlantic Ocean from the northeastern United States to Puerto Rico, the Lesser Antilles, or northern South America. This route averages 3,000 km over water, necessitating a potentially nonstop flight of up to 88 hours. To accomplish this flight, Blackpoll Warblers nearly double their body mass and take advantage of a shift in prevailing wind direction to direct them to their destination.
The species is poorly known on its South American wintering grounds, where it primarily travels in mixed species flocks with other migrants.
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