Bicknell’s Thrush (BITH)
Catharus bicknelli
Range
Bicknell’s Thrushes breed in the Northeastern United States and just north of this region in Canada. Their nonbreeding territory is located in the Caribbean Island region.
Additional Maps
Identification
The Bicknell’s Thrush is a medium-sized thrush that is generally difficult to observe due to its wary attitude. It is most similar to the Gray-cheeked Thrush, with the following color modifications. Most Bicknell’s Thrushes have olive-brown or brown dorsal coloration and a contrast between the chestnut-tinged tail and wings with the rest of the upper body. The upperparts have a warmer brown coloration and lighter buffy wash on the breast. The beak is bright yellow to yellow-orange at the base of the lower mandible. The legs are purplish pink and with pinkish to pale yellow feet.
The most notable call during breeding season is a harsh downward slurred whistle, which sounds like beer, veer, peert, queep, or quee-a. Both the intensity and pitch are highly variable. Additional calls of alarm and aggression sound like chatter or crr-rr-rr. Near nests, adults may also let out a low-pitched chook-chook or chuck-chuck, as well as a high-pitched weee whistle. The song can be described as chook-chook, wee-o, wee-o, or wee-o-ti-t-ter-ee. This song is typically sung by males, but females sometimes sing as well, though their song sounds whisperingly thin.
Habitat
This bird is known to breed in montane (mountain) forests dominated by balsam fir. The densest populations can be found in recently disturbed areas undergoing succession (standing dead conifers and regrowth of fir trees), especially where there are high winds and heavy ice accumulation along exposed ridgelines, as well as sections of industrial forest which are regrowing after harvest. The species does not typically inhabit interior forests. It is instead adapted to mosaic forests that undergo frequent changes from both natural and human disturbances.
There is little information about where Bicknell’s Thrushes prefer to inhabit during migration. They’re reported to inhabit more general habitats compared to nesting and breeding season, living in areas along well-vegetated beaches, dense woodlots, and open orchards and gardens, for example. There is little evidence that montane forests are preferred during migration.
Bicknell’s Thrush prefer mesic to wet montane forests for overwintering habitat in the Caribbean Island region, particularly in the Dominican Republic.
Conservation Status
- Listed as Vulnerable by the International Union for Conservation of Nature (IUCN)
- On the Conservation Concern Red Watch List by Partners in Flight
- Listed as an Orange-Alert Species by Road to Recovery
- Listed as Special Concern by the New York State Department of Environmental Conservation
- Listed as Special Concern by the New Hampshire Fish and Game Department
Threats to Conservation
Degradation of habitat is a major issue, especially in areas with red spruce dieback and mortality of balsam fire. Acidic ions in the atmosphere from industrial sulfur and nitrogen oxides are (inconclusively) implicated in the cause for red spruce decline. Increased winter-freezing also causes damage to spruce due to reduced calcium reserves linked to high levels of acid in precipitation. Although atmospheric sulfate levels have declined since the 1990 Clean Air Act, precipitation acidity in Northeastern North America does not seem to be decreasing.
Also implicated in the decline of montane forests is heavy metal toxicity from airborne pollutants. Airborne mercury is higher in the montane forests of Vermont and in the Catskills than in surrounding low-elevation areas. Bicknell’s Thrushes are vulnerable to mercury in these breeding sites, especially male birds who tend to consume more contaminated food sources, which can cause biomagnification.
Balsam-fir forests may also be impacted by global climate change long-term. Models predict a loss of half of this species’ breeding habitat over the next 30 years due to warming climates. Human development for recreation and commercialization is an additional risk factor, causing fragmentation of montane forests.
Funding Opportunities
- Agricultural Conservation Easement Program (ACEP)
- America the Beautiful Challenge
- Delaware River Program
- Delaware River Watershed Initiative
- Environmental Quality Incentives Program (EQIP)
- Land Trust Bird Conservation Initiative Small Grant Program
- The Migratory Bird Program
- Northeast Forests and Rivers Fund
- Northeast Wilderness Trust
- Regional Conservation Partnership Program (RCPP)
- Sustainable Forestry Initiative (SFI) Conservation Grants Program
General Management Guides
Regional Management Guides
Resources
- All About Birds: Bicknell’s Thrush
- Audubon: As Climate Change Threatens to Push the Bicknell’s Thrush North, Scientists Are Protecting Its Future Habitat Now
- Audubon Bird Guide
- Bicknell’s Thrush: A canary in the coalmine for climate change
- Conservation Assessment for Bicknell’s Thrush
- Oxford Academic: Genetic structure and biogeographic history of the Bicknell’s Thrush/ Gray-cheeked Thrush species complex