Stopover dynamics of boreal breeding songbirds at a northern stopover site

Abstract

Migratory bird stopover ecology, including stopover duration, refueling rates, and departure decisions are driven by inherent species traits and environmental conditions. Migratory displacements following stopover events may differ across migration strategy and energetics mediated by individual capacity, such as fuel loads. As analytical techniques and technologies grow more refined, so does our understanding of stopover ecology. By integrating 20 years of banding-recapture data and 2 years of telemetry-tracking, we quantified stopover ecology of 4 species of boreal-breeding birds at a peri-urban stopover site in Montreal, Quebec, Canada. Modeling techniques to estimate stopover length from banding and recapture data underestimated telemetry-based stopover duration for most species. Average fuel deposition rates were positive for all species during stopover, with refueling rate higher for individuals arriving in poorer condition and for a frugivore specialist (Catharus guttatus; Hermit Thrush). Following stopover, 3 species migrated primarily west of Appalachians, while the fourth species (Setophaga coronata; Yellow-rumped Warbler) migrated primarily east. Environmental conditions consistently influenced departure decisions, whereas the roles of stopover duration and refueling varied among species and migration strategy, underscoring the need to refine migratory theory and conservation planning.