New York Natural Heritage Program
Bicknell's Thrush
Catharus bicknelli (Ridgway, 1882)
Birds

Threats [-]
At the inaugural meeting of the International Bicknell's Thrush Working Group in November 2007, habitat loss on the wintering grounds in Hispaniola was ranked by experts as the most critical threat to this species. On the breeding grounds in the northeast, climate change, inducing reduced coverage of spruce/fir forests also presents a potential threat (Rodenhouse et al. 2007). Other potential breeding habitat threats addressed by the working group included ski resort and wind tower development, acid precipitation and other toxic deposition (especially mercury), recreational hiking, and predation by red squirrels.

Conservation Strategies and Management Practices [-]
The majority of occupied peaks in New York are within the state-owned forest preserve in the Catskills and Adirondacks, so extensive site-specific management is precluded. Most key demographic parameters were found not to be significantly different between existing ski areas in the northeast and natural forests. Limited ski trail development (i.e., disturbance) may not be overly detrimental if implemented properly (Rimmer et al. 2004). A new Unit Management Plan for Whiteface Mountain Ski Area included recommendations to minimize the potential negative impacts of new trail development on Bicknell's Thrushes. These included reducing trail width, managing the edges of trails and the establishment of a Conservation Fund to help protect the species on its wintering rounds in Hispaniola (Rimmer et al. 2004). Degradation of both wintering and breeding ground habitat will require larger scale policy solutions that can't be implemented solely within New York State.

Research Needs [-]
Preliminary data indicate that population size fluctuates with the biennial cycle of balsam fir cone crops, which correlates to elevated predator (red squirrels, chipmunks, voles) populations and depressed reproductive success in summers following high cone crops. There is also evidence for density-dependent population regulation on the breeding grounds (Rimmer et al. 2001). Thus, research is critically needed to disentangle the limiting factors regulating population distribution and abundance. Despite the fact that the most critical threats appear to be on the wintering grounds, if population regulation occurs primarily on the breeding grounds, mitigating wintering ground threats may be of lesser importance. Also, this species' naturally fragmented habitat suggests that metapopulation and source/sink dynamics may be relevant, and there is some evidence for this (Ellison 2001; Hobson et al. 2001). Further analyses of Mountain Birdwatch long-term data will be necessary to tease apart population dynamics.