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. Blackpolls winter in northern South America, undertaking extraordinarily long fall migrations to get there.
Largely because of the remoteness of both its breeding and wintering ranges, several aspects of this species' biology have not been extensively studied, particularly in the heart of its range. Detailed information on breeding biology comes from Kent Island, New Brunswick (Eliason Eliason 1986b , Eliason 1986a ), the Green Mountains, VT (McFarland and Rimmer unpubl. data), the White Mountains, NH (WVD) and Newfoundland (Taylor and Krawchuk 2005, Leonard et al. 2008, Dalley et al. 2008, 2009). Breeding season and annual survival (Whitaker et al. 2008), as well as habitat use by juvenile birds, has been examined in a managed and patchy landscape in Newfoundland (Mitchell et al. 2010, Mitchell et al. 2009), but the species remains poorly studied across the bulk of its range west to Alaska.
Another aspect of the species' breeding biology that has received at least minimal study is habitat use ( Morse 1979a , Sabo 1980 ), but again this research has been 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.
The species has been well-studied in fall migration. Blackpoll Warblers undertake the longest migration of any North American warbler, with some individuals traveling over 8,000 km from Alaska to Brazil ( Williams et al. 1977a , Nisbet et al. 1995a ). 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, Blackpolls 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.