eWestern BirdsThe Quarterly Journal of Western Field Ornithologists
Vol. 45, No. 4
Western Field Ornithologists
Characteristics of Sites of Western Bluebird Nests in Managed Ponderosa Pine Forests of Washington
Jeffrey M. Kozma
ABSTRACT: I compared characteristics of sites of Western Bluebird (Sialia mexicana) nests in natural tree cavities in burned and unburned logged ponderosa pine (Pinus ponderosa) forests along the east slope of the Cascade Range of Washington, 2003–2008 and 2010. Tree density and percent debris cover (litter and large woody debris) were greater at nest sites in unburned stands because fire kills live trees and consumes woody debris, and they were the only characteristics in which nest sites in burned and unburned forests differed. In burned stands cavities were oriented primarily east, whereas in unburned stands they were oriented randomly. East-facing cavities may be thermally advantageous early in the day, keeping eggs warmer when the incubating female is away foraging. Most snags containing bluebird nest cavities (73%) were advanced in decay and had broken tops. Of the cavities whose original excavator was known, 27% were excavated by the Hairy Woodpecker (Picoides villosus), 12% by the White-headed Woodpecker (P. albolarvatus), and 5% by the Northern Flicker (Colaptes auratus). Only one nest was located in a non-excavated cavity. Of the 38 second nests, 76% were in the same cavity as the first, even though 38% of these first attempts were unsuccessful, suggesting that suitable cavities are limiting. My results suggest that bluebirds use similar nest sites in burned and unburned ponderosa pine stands and that abandoned woodpecker cavities are critical to the Western Bluebird in these managed forests.