Forest patch size and breeding territory selection by coastal swainson's thrush (Catharus ustulatis ustulatis) in BC's Georgia Basin

Abstract

Many of North America's 250 species of Neotropical migrant songbirds have declined in the 20th and early 21st centuries. Forest fragmentation can introduce limiting factors to bird habitats as edge to interior ratios increase with potentially harmful related impacts. Avian habitat fragmentation research is biased towards Eastern North America. A breeding study of the coastal population of Swainson's thrush (Catharus ustulatus ustulatis) in the Georgia Basin was conducted with the research question: What effect does forest patch size have on Swainson's thrush breeding territory selection? Four forest patches representing a broad range of sizes were used, with control for additional environmental variables. Exhaustive avian sampling in the breeding season focused on density, abundance and habitat use. There were statistically significant causal relationships between forest patch size and total avian density and abundance. Density increased in smaller forests while total abundance declined. The study also covered the management implications of the research findings.