Cross-scale habitat selection reveals within-stand structural requirements for fledgling Golden-winged Warblers

The post-fledging period remains one of the most understudied portions of the avian lifecycle despite the fact that fledglings require resources distinct from those used during nesting. Post-fledging research can further inform breeding grounds management actions and improve conservation outcomes. While the Golden-winged Warbler (Vermivora chrysoptera) is known to make stand-level habitat shifts between nesting and post-fledging, the microhabitat conditions selected by fledglings remains unknown. We used cross-scale habitat selection analyses to evaluate the stand-specific microhabitat conditions required by fledgling Golden-winged Warblers in Pennsylvania. From 2014 through 2017 we radio-tagged and tracked 98 fledglings associated with 80 different sub-broods. We documented habitat use and compared habitat between fledgling and nest sites. Fledglings selected areas with dense overhead and lateral vegetation across stand types. Rubus cover and stem density of >2 m saplings were important in stand initiation and stem-exclusion stage stands, respectively. In mature forest upland and forested wetlands, fledgling Golden-winged Warblers selected for patches with lower basal area relative to what was available. Compared to nest sites fledgling locations contained less herbaceous cover and greater overhead vegetation density apparently provided by taller woody vegetation. Our findings suggest that management actions have high potential for creating post-fledging Golden-winged Warbler habitat, especially if factors such as invasive species and over-browsing are controlled during the regeneration stage of stands. Managers may need to take a proactive approach to create the structure required by fledglings in mature forest stand types where largely intact canopies inhibit understory regeneration. Existing management guidelines for the species should be updated to account for the unique vegetation structure required by fledglings during this stage of the lifecycle.