Meeting Abstract

S3-2.3  Friday, Jan. 4  Beat by beat on the move: Wing beat and heart rate of New World thrushes during migration in the wild WIKELSKI, Martin; Princeton Univ. wikelski@princeton.edu

Billions of songbirds around the world spend many nights on the wing during spring and fall en route to breeding or wintering sites. Largely due to technical limitations of tracking such small aerial migrants, little is known about individual movement pattern and their relationship to environmental parameters. However, biotelemetry devices are now miniaturized enough to allow for the continuous monitoring of small animals in the wild. We followed 15 complete nocturnal migratory flights of three species of Neotropical thrushes in the Midwestern US and recorded individual wing beats, flight speeds, body accelerations, and heart rates in some individuals. From over the 2-11 hours of individual flight durations, we documented high variability in: 1) wing beat frequencies (>20%), 2) body acceleration (>30%), 3) wing beat pausing (up to 60%), and 4 ground speeds (3-fold). A strong correlation of wing beat with heart rate in individual birds suggests that this variability is potentially ecologically (energetically) relevant. In particular, pauses in wing beat patterns appear to be related to lowered heart rate and thus lowered energy expenditures. We discuss potential environmental and biological causes of variability in flight patterns of thrushes and show how future experiments can distinguish between the various explanatory hypotheses.