Flight call response and energetics: two case studies analyzing migratory biology in select passerines on the south shore of Lake Ontario

Abstract

Passerine migration is an energy-intensive behavior that occurs during spring and autumn, often between distant breeding and wintering grounds. Stopover sites provide places to rest and refuel. This two-part collaborative thesis studied extrinsic and intrinsic factors that affected the behavior and energetics of migratory passerines that visited Braddock Bay Bird Observatory (BBBO), located on the south shore of Lake Ontario. First, we compared the conspecific flight-call response of 2 parulid species captured spring 2018 and 2019 during the day and at dusk. Responsiveness was much lower at dusk, which suggests flight-call communication is likely not an important feature of dusk departure in parulids. Second, we constructed seasonal path models using BBBO bird banding data from 1999-2016 to examine the impacts of extrinsic (i.e., capture date and hour captured) and intrinsic (i.e., age and sex) factors on the energetic condition of 3 Catharus thrushes. Capture date was the most important predictor of condition followed by age and hour, except when sex was included in our models. However, analyses of sex were limited (and potentially inflated) because we could only determine the sex of the largest and smallest individuals in one species, the Swainson’s Thrush (C. ustulatus). Both studies showed that extrinsic and intrinsic factors have important implications on passerine migration behavior and physiology and that migratory behavior is complex and worthy of additional investigation.