Point Transect Sampling for Monitoring Passerine Birds in Denali National Park and Preserve

Passerine birds (passerines) in Denali National Park and Preserve (Denali) have been selected for long-term monitoring as part of the National Park Service's (NPS) Inventory and Monitoring Program. Monitoring goals include relating bird distributions to habitat characteristics and detecting severe population declines over 20 years. Point transect surveys were implemented to monitor breeding passerines because distance sampling methods adjust counts for probability of detection, require only 1 visit to each sampling point during a breeding season, and allow monitoring of multiple species because males are easily identified by their songs. Our objectives were to analyze pilot data to 1) assess adherence to assumptions of distance sampling, 2) examine factors influencing detection probabilities, 3) estimate density across years and habitats, and 4) examine statistical power to detect future population declines.