This species, named for the black forehead and crown of the breeding male, has the longest migration of any North American warbler. Each fall, blackpolls migrate more than 2,000 miles across open water without stopping. They sometimes fly for more than 80 hours at a time until they reach their Amazon wintering grounds.
Like all warblers, blackpolls migrate principally at night, when they risk collision with brightly lit communications towers and buildings. Their boreal breeding grounds are at risk from industrial development, which destroys nesting habitat, and climate change.
Blackpolls have an elliptical migration, traveling a different route in the fall and in the spring. They are one of only two North American warbler species that winter in the Amazon Basin; the other is the Connecticut Warbler. In Brazil, blackpolls share habitat with birds like the Green-headed Tanager.
The blackpoll has a very high-pitched song—so high that many people have trouble hearing it at all. The birds also have a rather slow and deliberate feeding style, tending to stay in treetops as they glean insects and spiders from branches.
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Interestingly, this warbler has a high incidence of double brooding; by breeding more than once per nesting season, the birds produce a higher number of offspring than in many other species. Some males have more than one mate, a breeding system known as polygyny. Females tend to return to nest sites of the previous year, even if a different male is holding the territory.
Common, Yet Declining
Although still common, the North American Breeding Bird Survey shows that blackpoll populations are declining in the southern part of their range. The 2014 State of the Birds Report lists the Blackpoll Warbler as a common bird in steep decline.
Canada has taken steps to protect large areas of its boreal forest, preserving millions of acres of habitat for the blackpoll and other species dependent on these lands, including Canada Warbler, Swainson's Thrush, and Rusty Blackbird.
In addition, the “Boreal Birds Need Half” campaign, endorsed by ABC and many other groups, is working to conserve habitat necessary for these and many other migratory birds.
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