NCASI comments on Bicknell’s thrush

The U.S. Fish and Wildlife Service (Service) recently announced a 90-day finding on a petition from the Center for Biological Diversity (CBD) requesting that the Bicknell’s thrush (Catharus bicknelli) be listed as threatened or endangered under the Endangered Species Act and that critical habitat be designated (77 Federal Register 48934–48947). The Service has decided that the petition presents substantial scientific or commercial information indicating that listing the Bicknell’s thrush may be warranted. Thus, the Service has initiated a status review for the thrush and is requesting scientific and commercial data and other information regarding the status of and threats facing the species throughout all of its range.

The Bicknell’s thrush breeds in portions of the northeastern United States and southern Canada, and winters in the Greater Antilles. On the breeding range, it largely occurs in forests dominated by red spruce (Picea rubens) and balsam fir (Abies balsamea) and containing other tree species such as white birch (Betula papyrifera var. cordifolia). Total population size is estimated to be approximately 95,000 to 126,000 individuals (77 FR 48936).

The CBD petition alleges that the primary factor affecting the Bicknell’s thrush is the potential influence of climate change on habitat availability. The petitioners also assert that acid and nitrogen deposition, ground-level ozone, recreational and wind energy development, precommercial thinning, predation, and many other factors are affecting the species.

NCASI has submitted technical comments on the 90-day finding to the Service. Best available information indicates that the Bicknell’s thrush population in the United States is stable or increasing. Concerns about potential future effects of climate change are speculative and do not constitute evidence of a substantial threat to the viability of Bicknell’s thrush in the foreseeable future. Although studies have documented reduced density of Bicknell’s thrush in precommercially thinned stands for 1-3 years following thinning, Bicknell’s thrush continue to occur and nest in thinned stands; abundance increases within 4 years post-thinning; and use of precommercial thinning appears to be unrelated to range-wide estimates of population trends for Bicknell’s thrush. In conducting its status review, the Service should focus on factors shown to have effects on population viability, and they should keep in mind that many animal species are naturally uncommon. Thus, a small population size alone is an inadequate basis for assessing extinction risk or listing under the Endangered Species Act.  

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