| Blackpoll Warbler | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Parulidae |
| Genus: | Dendroica |
| Species: | D. striata |
| Binomial name | |
| Dendroica striata (Forster, 1772) |
|
The Blackpoll Warbler, Dendroica striata , is a New World warbler. Breeding males are mostly black and white. They have a prominent black cap, white cheeks and white wing bars. The Blackpoll breeds in northern North America, from Alaska, through most of Canada, and into the Great Lakes region and New England.
They are migratory, wintering in northwestern South America. They are rare vagrants to western Europe, although their northerly range and long-distance migration make them one of the more frequent transatlantic passerine wanderers.
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The Blackpoll Warbler measures 4 inches in length and weighs about 10 grams, the weight of a ball point pen.[1] 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.
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. They also spend their summers on the wooded coastal islands of Maine and the Maritime Provinces. Father North they have been reported throughout the boreal coniferous forest. Blackpolls breed nearer to the tundra than any other warbler.[2]
The Blackpoll seems to flit along the trunk of a tree without touching it.
Their songs are simple repetition of high tsi notes. Their calls are thin sits.
They birds are insectivorous, but will opt for berries in winter. They often forage high in trees, and sometimes catch insects while in flight.
Their breeding habitats are coniferous woodlands, especially those in which spruce trees grow. These birds' breeding ranges extends to the taiga. Blackpoll Warblers commonly nest in a relatively low site which can be found in a conifer, and they lay 4-9 eggs in a cup-shaped nest.
The Blackpoll is the latest of the spring warblers to come north.
Baird describes the Fall migration of the Blackpoll. From their breeding grounds across the northern latitudes, they converge on the Northeastern United States south to Virginia starting in mid-August.[3] As they forage in the staging area, the birds will often double their weight in fat. Then they fly southward over the Atlantic burning, according to Baird, .08 grams of fat every hour. They travel about 27 miles per hour. Their oceanic flight covers over 2000 miles and takes about 80 hours. Blackpolls weigh up to 20 grams when the leave the United States and lose 4 or more grams by the time they reach South America. Some of the Blackpolls land in Bermuda before going on. Some birds, often with lower body weights, don't make it.[4]
The Blackpoll Warbler's transoceanic flight has been the subject of over twenty-five scientific studies. Sources of data include radar observations, bird banding and weights taken, dead birds recovered from field sites and fatal obstacles.[5]
Island stopovers at Bermuda and other places have been cited as evidence of migratory pathways. Baird's conclusion, stated above, differed from Cooke (1904, 1915) and Murray (1965, 1989). Cooke and Murray contended that the Blackpoll Warbler migrates to South America along the mainland of southeastern North America. Baird, Nisbet and others argued that most Blackpoll Warblers fly directly from northeastern North America over the Atlantic Ocean to their winter range. They used data from nocturnal accidents, banding stations and sightings to state that Blackpoll Warblers are rare autumn migrants south of Cape Hatteras, North Carolina, whereas north of Hatteras they are common. Those holding to a direct oceanic pathway pointed to this evidence to support their hypothesis.[6]