Nest Boxes Facilitate Local-Scale Conservation of Common Goldeneye (Bucephala clangula) and Bufflehead (Bucephala albeola) in Alberta, Canada

We tested the general predictions of increased use of nest boxes and positive trends in local populations of Common Goldeneye (Bucephala clangula) and Bufflehead (Bucephala albeola) following the large-scale provision of nest boxes in a study area of central Alberta over a 16-year period. Nest boxes were rapidly occupied, primarily by Common Goldeneye and Bufflehead, but also by European Starling (Sturnus vulgaris). After 5 years of deployment, occupancy of large boxes by Common Goldeneye was 82% to 90% and occupancy of small boxes by Bufflehead was 37% to 58%. Based on a single-stage cluster design, experimental closure of nest boxes resulted in significant reductions in numbers of broods and brood sizes produced by Common Goldeneye and Bufflehead. Occurrence and densities of Common Goldeneye and Bufflehead increased significantly across years following nest box deployment at the local scale, but not at the larger regional scale. Provision of nest boxes may represent a viable strategy for increasing breeding populations of these two waterfowl species on landscapes where large trees and natural cavities are uncommon but wetland density is high.

The Influence of Summer Climate on Avian Community Composition in the Eastern Boreal Forest of Canada

Understanding the relative influence of environmental variables, especially climate, in driving variation in species diversity is becoming increasingly important for the conservation of biodiversity. The objective of this study was to determine to what extent climate can explain the structure and diversity of forest bird communities by sampling bird abundance in homogenous mature spruce stands in the boreal forest of the Québec-Labrador peninsula using variance partitioning techniques. We also quantified the relationship among two climatic gradients, summer temperature and precipitation, and bird species richness, migratory strategy, and spring arrival phenology. For the bird community, climate factors appear to be most important in explaining species distribution and abundance because nearly 15% of the variation in the distribution of the 44 breeding birds selected for the analysis can be explained by climate. The vegetation variables we selected were responsible for a much smaller amount of the explained variation (4%). Breeding season temperature seems to be more important than precipitation in driving variation in bird species diversity at the scale of our analysis. Partial correlation analysis indicated that bird species richness distribution was determined by the temperature gradient, because the number of species increased with increasing breeding season temperature. Similar results were observed between breeding season temperature and the number of residents, short-distance and long-distance migrants, and early and late spring migrants. Our results suggest that the northern and southern range boundaries of species are not equally sensitive to the temperature gradient across the region.

Predicting origins of passerines migrating through Canadian migration monitoring stations using stable-hydrogen isotope analyses of feathers: a new tool for bird conservation

The Canadian Migration Monitoring Network (CMMN) consists of standardized observation and migration count stations located largely along Canada’s southern border. A major purpose of CMMN is to detect population trends of migratory passerines that breed primarily in the boreal forest and are otherwise poorly monitored by the North American Breeding Bird Survey (BBS). A primary limitation of this approach to monitoring is that it is currently not clear which geographic regions of the boreal forest are represented by the trends generated for each bird species at each station or group of stations. Such information on “catchment areas” for CMMN will greatly enhance their value in contributing to understanding causes of population trends, as well as facilitating joint trend analysis for stations with similar catchments. It is now well established that naturally occurring concentrations of deuterium in feathers grown in North America can provide information on their approximate geographic origins, especially latitude. We used stable hydrogen isotope analyses of feathers (δ²Hf) from 15 species intercepted at 22 CMMN stations to assign approximate origins to populations moving through stations or groups of stations. We further constrained the potential catchment areas using prior information on potential longitudinal origins based upon bird migration trajectories predicted from band recovery data and known breeding distributions. We detected several cases of differences in catchment area of species passing through sites, and between seasons within species. We discuss the importance of our findings, and future directions for using this approach to assist conservation of migratory birds at continental scales.