Preferred Session: Natural History of Birds

Abstract:

Sex-based habitat segregation in passerines is most commonly documented on wintering grounds with growing evidence of its importance during migration. However, sex-based habitat segregation in passerines on their breeding grounds is poorly represented in the literature. An examination of perch height, perch exposure, and prey-capture site exposure as part of a 20-year study of leg-banded Southwestern Willow Flycatchers (Empidonax traillii extimus) in San Diego County demonstrates significant differences between sexes. Possible explanations for sexual segregation include differential forage selection, reduction of depredation risk in relation to activity budgets, higher reproductive success, and possible enhancement of genetic health. The latter two factors may may be of specific relevance to semi-colonial species given the high level of “stolen copulations” reported (and in this study, observed) and which result in extra‐pair paternity. My findings recommend specific habitat management, restoration, and habitat creation strategies that address the needs and preferences of both sexes, a missing element in habitat management and recovery planning for this endangered species.