Habitat Associations of the Eastern Whip-poor-will (Antrostomus vociferus) in a Heterogeneous Landscape

摘要

The Eastern Whip-poor-will (Antrostomus vociferus) is a nocturnal bird whose abundance is declining throughout much of its breeding range. The reasons for this decline are unknown, but loss of suitable breeding habitat has been implicated. We established 60 study sites in five counties of central Wisconsin to study habitat associations of breeding Eastern Whip-poor-wills. Sites included dry upland forest tracts of >1 ha. We measured 14 microhabitat variables at each site to describe forest structure. Tree species composition and soil structure also were determined for each site. Factor analysis was used to derive a smaller subset of composite habitat variables, and logistic regression analysis was used to relate presence-absence of Eastern Whip-poor-wills to the composite habitat variables, tree species composition, and soil structure. Singing male whip-poor-wills were present at 30 sites and absent from 30 sites. Presence of whip-poor-wills in a tract was related negatively to composite variables representing herb cover, forest stature, and understory density. Presence of Eastern Whip-poor-wills was related positively to proportion of Pinus banksiana and negatively to Fraxi-nus pennsylvanica, Acer rubrum, and Quercus alba in a tract. Whip-poor-wills also were associated with soils with increasing sand content. Thus, presence of Eastern Whip-poor-wills was related positively to younger forest tracts with an open understory dominated by pioneer tree species that thrive in sandy soils, but they avoided more mature tracts with more undergrowth and later-successional or mesic species and water-retaining soil. Preserving forested tracts adjacent to open recently-cleared areas may ensure the persistence of Eastern Whip-poor-wills in central Wisconsin and elsewhere.