Cameron J. Nordell and Erin M. Bayne, Department of Biological Sciences, University of Alberta
2016
Executive Summary
The Rusty Blackbird (Euphagus carolinus) was listed as Special Concern on Schedule 1 of the federal Species at Risk Act (Government of Canada / Gouvernement du Canada 2009) in March 2009 because of large and long-term declines in population size. The Rusty Blackbird is a medium-sized, insectivorous subtropical migrant Icterid. It breeds in wetland habitats in the boreal forests of North America (bogs, fens, swamps, and ponds) and winters in the southeastern United states, into Mexico. Approximately 85.5% and 8.4% of the global breeding range of Rusty Blackbirds are found in Canada and Alberta, respectively. Once considered an abundant species, they are generally uncommon across their range today. Breeding Bird Survey (BBS) data, the primary source of trend estimates in Canada, indicate that the Rusty Blackbird population in Alberta and Canada has declined substantially since the mid 1960’s. However, there are substantial methodological problems with this data, leading to uncertainty, especially in regions of the breeding range that have been infrequently sampled. The use of Automated Recording Units (ARUs) deployed by the Bioacoustic Unit (BU; University of Alberta) can improve data about Rusty Blackbird populations in Alberta, specifically in the under-sampled Lower Athabasca Watershed region. ARUs deployed at 2399 stations throughout the region from 2012 -2016 detected all nearby vocal animals. Generally, ARUs appear to detect Rusty Blackbirds at a higher rate (>1 % of surveys) than previous methods. Using mixed effects logistic regression, Rusty Blackbird detection probabilities were shown to be greater in fen habitats, increase linearly with latitude and, marginally increase with distance from roads. However, 82.1% (198 / 241) detections occurred at stations nearby the McLelland Lake Fen Complex. Thus, the data suggests large, intact, and possibly remote, wetland complexes may be important areas for the remaining Rusty Blackbird populations in Alberta, and across the breeding range and should be surveyed. Conservation efforts intended to protect Rusty Blackbirds in the Lower Athabasca Watershed region need to address issues related to development near the McLelland Lake Fen Complex, where Rusty Blackbirds were detected in >5% of all surveys.
16-ERPC-08J