Comparison of point counts and territory mapping for detecting effects of forest management on songbirds

摘要: Point counts are commonly used to assess changes in bird abundance, including analytical approaches such as distance sampling that estimate density. Point-count methods have come under increasing scrutiny because effects of detection probability and field error difficult quantify. For seven forest songbirds, we compared fixed-radii (50 m 100 m) density estimates obtained from known numbers birds determined by territory mapping. We applied point-count analytic a typical management question results those before–after control impact (BACI) analysis with data set collected across study areas the central Appalachians 2006 2010. Using 50-m fixed radius, variance was at least 1.5 times other methods, whereas 100-m radius underestimated actual >3 territories per 10 ha for most abundant species. Distance improved accuracy precision fixed-radius counts, although were affected counted outside 10-ha units. In BACI analysis, mapping detected an overall treatment effect five species, generally consistent each year. contrast, all failed detect two due annual estimates. Overall, our highlight need adequate sample sizes reduce variance, skilled observers level data. Ultimately, advantages disadvantages different survey should be considered context design objectives, allowing trade-offs among effort, accuracy, power effects.