Bicknell’s Thrush
The History, Range, and Conservation Status of Bicknell’s Thrush
After more than a century Bicknell's Thrush, Catharus bicknelli, gained its own species designation. The next century may record its decline.
History of Bicknell’s Thrush
Bicknell’s Thrush was discovered in 1881 by Eugene P. Bicknell, but it did not officially become a species – Catharus bicknelli – until 1995, based largely on the work of Dr. Henri Ouellet and DNA studies. The problem was that Bicknell’s Thrush looks almost identical to the Gray-cheeked Thrush, especially if you are observing the bird in the wild. If you have the two birds in hand, however, Bicknell’s thrush is smaller and has yellow colour at the base of the lower bill. The two birds have different calls, different ranges, and differences in DNA, all factors which support the decision that they are two different species.
Natural History and Habitat of Bicknell’s Thrush
Bicknell’s Thrush is found only in northeastern North America - both Canada and the United States have populations in isolated patches from southeastern Quebec and northern Nova Scotia, south to the Catskills of New York. The birds migrate south to the Dominican Republic, Haiti, Jamaica, Puerto Rico, and Cuba for the winter.
During the breeding season, Bicknell’s Thrush prefers disturbed or stunted forest, particularly montane forests (wet forest at high elevations): the dense stunted forests found in exposed chilly areas of Eastern Canada, areas regenerating after storm or fire damage, and natural or planted regrowth in forestry clearcuts. The patchy distribution of this type of habitat explains the similarly patchy distribution of Bicknell’s Thrush. In its winter range, Bicknell’s Thrush also frequents high montane forests.
Nesting begins in June with three or four chicks being reared in nests constructed of twigs and moss. Females mate with more than one male, producing broods with mixed paternity, and chicks are fed by both male and female birds with some nests receiving contributions from several males. During the breeding season, Bicknell’s Thrush eats primarily insects and other arthropods; fruit is added to the diet in the winter months.
Threats to Bicknell’s Thrush
The fact that Bicknell’s Thrush tends to inhabit areas far from people makes it seem very rare, elusive, and difficult to study. Indeed, even where the bird is found, it is more often heard than seen. In its summer range, the species is threatened by loss of forest habitat due to forestry, acid rain, and climate change. However, the preference that Bicknell’s Thrush shows for disturbed forest, and habitat protection already in place, stand in its favor. Pressures are considerably worse in the winter range, with much of the montane forest in the Greater Antilles being cleared by humans.
Conservation Status
It’s clear that Bicknell’s Thrush is in a perilous position. The IUCN Red List lists the bird as vulnerable, while Canada’s Species at Risk Act classifies it as a species of special concern. In the Northeast United States, Bicknell’s Thrush is the Neotropical migrant of highest conservation priority.
Other articles about birds in northeastern North America:
Places to See Atlantic Puffins
The Glace Bay Western Reef Heron
Sources:
Audubon. “Bicknell’s Thrush.”
Bird Studies Canada. “Bicknell’s Thrush in New Brunswick’s Forests."
Environment Canada. “Bicknell’s Thrush.”
