Characterization of Worm-eating Warbler (Helmitheros vermivorum) breeding habitat at the landscape level and nest scale

The Worm-eating Warbler (Helmitheros vermivorum) is typically described as a mature forest species requiring moderate to steep slopes and dense understory vegetation for breeding. However, nesting microhabitat characteristics vary regionally. Given the extensive variation in landscape topography, forest composition, and habitat structure across the breeding range, identification of important local landscape features and microhabitat characteristics is needed to formulate and implement improved conservation actions for the species. We characterized important habitat associations at two distinct scales (the landscape scale and the nest scale) to provide a detailed description of Worm-eating Warbler breeding habitat requirements in southern Indiana. Results from our point count and nest searching surveys emphasize the importance of terrain variables (i.e., steep SW-facing slopes) within mature forest habitat in southern Indiana. In addition, the structural microhabitat variable, leaf-litter depth, was an important predictor at the nest scale. Our dual-scale characterization of important habitat associations during the nesting portion of the breeding season provides a more complete understanding of Worm-eating Warbler breeding ecology in this portion of its range