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Thrushes

Status Of North American Thrushes

  • Eastern bluebird (Sialia sialis) and Western bluebird (Sialia mexicana). Have suffered from the felling of dead trees and the removal of dead branches, which increases competition with other species such as House sparrows and European starlings for nesting cavities. Nest boxes are now used to maintain populations; this has proven more successful with the Eastern Bluebird, but the provision of nesting boxes for Western Bluebirds does not appear to have kept pace with the loss of natural sites. In recent decades, the numbers of Western bluebirds have declined over much of this bird's range. It is estimated that at one point, the Eastern bluebird population had declined by 90% since 1900; today the population seems to be increasing. Rarely, cowbirds may lay eggs in this bird's nests, with the result that fewer young of their own are hatched.
  • Mountain bluebird (Sialia currucoides). The population of this species has suffered drastic decline since 1900. This bird competes with flickers, swallows, house sparrows, and starlings for nesting locations. But today their numbers appear stable.
  • Townsend's solitaire (Myadestes townsendi). Rarely, cowbirds may parasitize.
  • Wood thrush (Hylocichla mustelina). Serious population decline in recent years. May be losing winter habitat in tropics. Cowbirds may parasitize.
  • Veery (Catharus fuscescens). Brown-headed Cowbirds may parasitize. Surveys suggest that this bird's numbers are declining.
  • Swainson's thrush (Catharus ustulatus). This bird no longer breeds along the Pacific Coast as it once did, although the overall population appears stable. It may be vulnerable to loss of breeding grounds. Rarely, cowbirds may parasitize.
  • Gray-cheeked thrush (Catharus minimus). The southern breeding populations may be in decline.
  • Bicknell's thrush (Catharus bicknelli). The Bicknell's thrush of the Northeast, which winters mostly on the island of Hispaniola in the West Indies, is currently being watched by conservationists. Although the Bicknell's Thrush looks and sounds very much like the Gray-cheeked Thrush, it is now considered to be a separate species. Unlike most Gray-cheeked thrushes, which breed in northern spruce forests and in thickets of willow and alder on the tundra, the Bicknell's thrush breeds in stunted conifers on the tops of mountains and in dense second-growth woods containing many young conifers.
  • Hermit thrush (Catharus guttatus). Numbers appear to be holding up. Because it winters farther north than other brown thrushes, it less threatened by ecological damage to the tropics. Rarely, cowbirds may parasitize.
  • Varied thrush (Ixoreus naevius). Although still common, this bird may be vulnerable to loss of habitat due to cutting of forests of the Northwest.
  • American robin (Turdus migratorius). Rarely, cowbirds may parasitize. Has expanded into Great plains and drier lowlands with the planting of trees and the extension of irrigation (creating nesting sites and moist grassland for foraging). Although this bird was once widely hunted for food, it is today abundant and widespread.
  • Northern wheatear (Oenanthe oenanthe). The population in North America appears stable, but this bird may be increasingly seeking out breeding grounds in northeastern Canada.
  • Bluethroat (Luscinia svecica). This small Alaskan population is probably stable, and possibly even increasing. Widespread and common in Eurasia.

See also Blackbirds.

Resources

Books

Brooke, M., and T. Birkhead, eds. The Cambridge Encyclopedia of Ornithology. Cambridge: Cambridge University Press, 1991.

Ehrlich, Paul R., David S. Dobkin, and Darryl Wheye. The Birder's Handbook. New York: Simon & Schuster Inc., 1988.

Forshaw, Joseph. Encyclopedia of Birds. New York: Academic Press, 1998.

Peterson, Roger Tory. North American Birds. Houghton Miflin Interactive (CD-ROM), Somerville, MA: Houghton Miflin, 1995.


Bill Freedman
Randall Frost

Additional topics

Science EncyclopediaScience & Philosophy: Thallophyta to ToxicologyThrushes - Biology Of Thrushes, Species Of Thrushes, Thrushes And People, Status Of North American Thrushes