The Western Bluebird (Sialia mexicana) is a secondary-cavity-nesting thrush that breeds in semi-open habitats throughout much of western North America. Historically, the Western Bluebird was more common in Washington west of the Cascade crest than to the east, but today it is more abundant in the eastern Cascades. The decline of Western Bluebird populations in western Washington and some other parts of the range is attributed to competition with the European Starling (Sturnus vulgaris) for cavities, “sanitation” of logged forest by removal of snags and defective live trees, and habitat loss due to increased urbanization and higher forest densities resulting from decades of fire suppression. It is important to understand the response of breeding Western Bluebirds to the various factors shaping their habitat, including management of forests for timber harvest. Thus, our goal is to investigate how the Western Bluebird’s breeding success and nest-site characteristics are related to current forest-management practices.
Our objectives were to (1) examine the temporal and spatial factors associated with variation in the daily survival rate of Western Bluebird nests and (2) document nest-initiation dates, clutch size, egg success (percentage of eggs resulting in fledged young), and fledging rates of Western Bluebirds in natural tree cavities.
To determine if there are vegetation/habitat variables that influence Western Bluebird nest-survival in natural tree cavities.
This project was completed in 2008 and the results published in the peer-reviewed journal The Condor in 2010. The .pdf for this published paper can be found by clicking on the link below.