Decline of a New Hampshire Bicknell's Thrush Population, 1993-2003

Catharus bicknelli (Bicknell's Thrush) is a rare inhabitant of mountain forests in the northeastern United States and southeastern Canada. Conservation planners consider the species to be at risk, although evidence of population decline has thus far been localized or inconclusive. In order to assess the status of Bicknell's Thrush in the White Mountains of New Hampshire, we conducted point-count surveys on 40 forested, high-elevation routes from 1993 to 2003. Non-linear regression oil aggregate counts revealed a 7% annual decline over this period (P < 0.1). We discuss possible threats to Bicknell's Thrush, including winter habitat loss, pollution of mountain ecosystems, climate change, and human intrusion during breeding. A range-wide monitoring program that incorporates new survey methods is needed to help identify limiting factors and reduce potential sources of error and bias. This study underscores the importance of efforts to monitor and conserve Bicknell's Thrush.