Effects of wind energy production on a threatened species, the Bicknell’s Thrush Catharus bicknelli, with and without mitigation

SummaryRenewable energy helps meet the growing energetic demand while reducing greenhouse gas emissions. Despite its environmental benefits, production of wind energy can adversely affect wildlife populations, including birds. In some species, indirect impacts such as habitat loss and disturbance may be more important than fatalities caused by collisions with turbines. Bicknell’s Thrush Catharus bicknelli, one of the most endangered bird species in North America, may be threatened by wind energy production because it breeds at high elevation sites, which are often prized for their wind potential. Our study had two objectives: we first aimed to document the impacts of the construction and operation of a wind energy facility without mitigation strategy on the occurrence of the Bicknell’s Thrush. At a second facility, we then tested the effectiveness of turbine micro-siting as an effective mitigation strategy to reduce the impacts of wind-energy development on the species. We conducted avian point-counts at 143 locations spread across both facilities in Quebec (Canada) at different periods: before, during and after construction. We modelled the probability of occurrence of the species at point-counts as a function of period, forest loss caused by wind energy development, distance to the nearest turbine and habitat suitability. At the facility without mitigation, we found that the probability of occurrence decreased during construction and early operation at high elevation sites, where most of the turbines were erected. However, the Bicknell’s Thrush recolonized high elevation sites eight years post-construction. In addition, we did not detect a significant impact of wind energy production on the species’ occurrence at the facility where micro-siting was applied. We conclude that habitat loss and disturbance during construction are the main impacts of wind energy production on the Bicknell’s Thrush and that micro-siting appears to be a promising mitigation strategy.

Comparing fall migration of three Catharus species using a radio-telemetry network

Migration routes vary greatly among small passerine species and populations. It is now possible to determine the routes over great distances and long periods of time with emerging monitoring networks. We tracked individual Swainson’s Thrush (Catharus ustulatus), Bicknell’s Thrush (Catharus bicknelli) and Gray-cheeked Thrush (Catharus minimus) in northeastern Quebec and compared their migration routes and paces across an array of radio-telelemetry stations in North America. Swainson’s Thrush migrated further inland than the other two species. Individuals from all three species slowed their migration pace in the southeastern United States, and Swainson’s Thrush was more likely to stopover than Bicknell’s Thrush. Although individuals were tagged in a small area within or close to their breeding range, the results document the variability of migration routes between species with similar ecological characteristics and provide detailed material to be used for migration studies with broader taxonomic or ecological scope.