Orientation of nocturnally migrating Swainson's thrush at dawn and dusk: Importance of energetic condition and geomagnetic cues
We studied the early morning cage orientation of nocturnally migrating Swainson's Thrushes (Catharus ustulatus) during three fall migration seasons. The results were compared with earlier free-flight release tests under starry skies and were found to be consistent with continuation of migratory flights in the expected seasonally appropriate direction. Energetic condition proved decisive: fat birds