Ecological factors explain habitat associations of mature-forest songbirds in regenerating forest clearcuts | Factores ecológicos explican las asociaciones de hábitat de pájaros de bosque maduro en claros de bosque en regeneración

Some mature-forest bird species use early-successional habitat to a great extent during the breeding season, but the specific drivers behind this habitat association remain poorly understood. In this study we identified important species-specific ecological factors contributing to early-successional site-use by mature-forest bird species during the breeding season. From 2015 to 2017, we used constant-effort mist-netting to survey breeding birds in six 7 to 9 year-old regenerating forest clearcuts in southern Indiana, and characterized early-successional habitat associations of the 6 most-frequently captured mature-forest bird species (Worm-eating Warbler [Helmitheros vermivorum], Ovenbird [Seiurus aurocapilla], Scarlet Tanager [Piranga olivacea], Wood Thrush [Hylocichla mustelina], Black-and-white Warbler [Mniotilta varia], and Red-eyed Vireo [Vireo olivaceus]). We collected detailed environmental covariate data to account for variation in food availability and habitat structure variables corresponding to each 10 d sampling period at the clearcut-site scale. We fit separate generalized linear mixed models, using a negative binomial error structure, for each of the 6 focal bird species captured within clearcuts. Both habitat structure and food availability variables were important predictors of site use for mature-forest birds in early-successional habitat. Vegetation density was included in best-fit models for 5 of the 6 mature-forest species. Fruit availability was included in best-fit models explaining Scarlet Tanager and Wood Thrush captures, and invertebrate dry mass was included in best-fit models for Worm-eating Warbler, Ovenbird, and Black-and-white Warbler. The varying importance of both habitat structure and food availability variables for multiple mature-forest bird species suggests that the factors influencing the use of early-successional habitat by mature-forest birds during the breeding season may differ among species.