Detection Probabilities of Woodpecker Nests in Mixed Conifer Forests in Oregon

Abstract

Accurate estimates of Black-backed (Picoides arcticus) and Hairy Woodpecker (P. villosus) nests and nest survival rates in post-fire landscapes provide land managers with information on the relative importance of burned forests to nesting woodpeckers. We conducted multiple-observer surveys in burned and unburned mixed coniferous forests in Oregon to identify important factors influencing detection rates of woodpecker nests. We found 21 Black-backed Woodpecker nests and 38 Hairy Woodpecker nests in burned forest, and three Hairy Woodpecker nests in unburned forest. Competing models of detection probability in Program MARK indicated that nest-detection probability differed by nest stage. We found no evidence to indicate that detection rates of nests were associated with survey timing during the nesting season. Raw nest counts in burned coniferous forests may underestimate nest numbers, especially for nests in early stages of development. Black-backed Woodpecker nests were slightly more detectable than those of Hairy Woodpeckers in burned forests, and observers may differ in their abilities to detect nests.