Meeting Abstract
Although the timing of bird migration is broadly controlled by internal and external annual clocks, weather-related factors such as temperature, wind speed and direction, and barometric pressure can influence the timing and success of migratory flights and stopover durations. Weather conditions differ across seasons for many North American songbirds, thus weather cues in autumn may influence birds differently than those same cues in the spring. In addition, the rate and synchrony of migration differs between spring and autumn for many songbirds. To explore how temperature may differentially affect migration across seasons, we experimentally exposed white-throated sparrows (Zonotrichia albicollis) to three temperature treatments during both autumn and spring migration and also gave birds a restricted or unlimited diet. We manipulated temperature each night to one of three conditions: 4 °C to represent a cold evening, 14 °C to represent average seasonal temperatures, or 24 °C to represent a warm evening. Each day, birds returned to 14 °C for the remainder of the day. We quantified nocturnal migratory restlessness (Zugunruhe) using infra-red video recordings and automated activity tracking software. Preliminary analyses indicate differential effects of migratory restlessness between seasons, with stronger effects of temperature in spring compared to autumn. In addition, we observed sex differences in spring, but not in autumn. These results provide evidence that birds can shift their migratory behavior depending on temperature and suggest that the importance of temperature as a cue for migration timing differs between spring and autumn.
