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Range and Habitat Needs

A habitat specialist on its North American breeding grounds, which include mountains of New York and northern New England, Quebec, and some maritime forests in New Brunswick and Nova Scotia. Within this limited and fragmented range, inhabits dense conifer forests at high elevations, generally > 900 m.
On wintering grounds in Hispaniola, Bicknell’s Thrush occurs over an elevational range from sea level to >2,000 meters, wherever moist broadleaf forests with a dense understory are found. Most of these habitats persist in mountainous areas, removed from the reach of humans. Core population centers for Bicknell’s Thrush in the Dominican Republic include Sierra de Bahoruco, Cordillera Central, Cordillera Septentrional, and Parque Nacional los Haitises. Recent surveys have also found the species in remnant forests of Haiti’s Macaya Biosphere Reserve and La Visite National Park.
Bicknell’s Thrush also occurs in Cuba’s Sierra de Maestra, Jamaica’s Blue Mountains, and very sparingly in Puerto Rico’s Luquillo Mountain foothills.

Habitat conservation is the key to ensuring the long-term viability of Bicknell’s Thrush populations. On its breeding grounds, careful regulation of development in montane forests, control of atmospheric pollution, and a reversal of global warming.
Because Hispaniola constitutes the winter stronghold of Bicknell’s Thrush, conservation of its habitats is crucial to the species’ survival. Deforestation must be curtailed and sustainable agricultural practices must be implemented.
Efforts must be made to better understand the ecology of females in winter and to conserve forest types that are critical for female survival.

Interesting Facts

Bicknell’s Thrush was “discovered” in the Catskill Mountains of New York in 1881 and considered a subspecies of the morphologically similar Gray-cheeked Thrush until 1995, when it gained full species status.
Bicknell’s Thrush has a very unusual mating system, in which 75% of nests are attended by > 2 males and paternity is highly mixed. The adult sex ratio on the breeding grounds is 2.2 males per female.
In winter, male and female Bicknell’s Thrush appear to segregate by habitat type. In undisturbed, primary broadleaf forests of Sierra de Bahoruco, males outnumber females by a 4:1 ratio. Both sexes maintain territories throughout the winter, although those of males are larger (0.35 vs. 0.2 hectares). Return rates of banded birds are fairly high, with at least 25% of thrushes returning from one winter to the next. These forests apparently represent optimal winter habitat for Bicknell’s Thrush.
A different situation exists in more disturbed, secondary broadleaf forest of the Cordillera Septentrional. Here females slightly outnumber males, and territoriality appears to be weak or nonexistent. Extremely few birds return from one winter to the next, and many may not even remain (or survive) on site during a single winter. It seems likely that these more open, disturbed forests are low quality habitat for Bicknell’s Thrushes, and that, because suitable forest habitat is limited islandwide on Hispaniola, females may few options but to inhabit them.

Where to Find More Information?

Rimmer, C.C., K.P. McFarland, W.G. Ellison, and J.E. Goetz. 2001. Bicknell’s Thrush (Catharus bicknelli). In The Birds of North America, No. 592 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

Latta, S. C., C. C. Rimmer, A. R. Keith, J. W. Wiley, H. A. Raffaele, K. P. McFarland, and E. M. Fernandez. 2006. Birds of the Dominican Republic and Haiti. Princeton University Press, Princeton, NJ.

BirdLife International. 2006. Species fact sheet: Bicknell’s Thrush. http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=30034&m=0

IUCN Red List. http://www.iucnredlist.org/search/details.php/40470/summ.

Bicknell's Thrush Bird of the Month contributed by Chris Rimmer (Vermont Institute of Natural Science)

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