Factors influencing the movement biology of migrant songbirds confronted with an ecological barrier

• Published in: Behavioral ecology and sociobiology 2013-12, Vol.67 (12), p.2041-2051
• Main Authors: Smolinsky, Jaclyn A., Diehl, Robert H., Radzio, Thomas A., Delaney, David K., Moore, Frank R.
• Format: Article
• Language: English
• Subjects: Aerial locomotion; Animal communication; Animal Ecology; Animal migration behavior; Behavioral biology; Behavioral Sciences; Biomedical and Life Sciences; Bird banding; Bird migration; Birds; Catharus ustulatus; Gulfs; Life Sciences; Migratory birds; Original Paper; Radio transmitters; Signals; Songbirds; Weather; Wind; Zoology
• ISSN: 0340-5443; 1432-0762
• DOI: 10.1007/s00265-013-1614-6

Whether or not a migratory songbird embarks on a long-distance flight across an ecological barrier is likely a response to a number of endogenous and exogenous factors. During autumn 2008 and 2009, we used automated radio tracking to investigate how energetic condition, age, and weather influenced the departure timing and direction of Swainson's thrushes (Catharus ustulatus) during migratory stopover along the northern coast of the Gulf of Mexico. Most birds left within 1 h after sunset on the evening following capture. Those birds that departed later on the first night or remained longer than 1 day were lean. Birds that carried fat loads sufficient to cross the Gulf of Mexico generally departed in a seasonally appropriate southerly direction, whereas lean birds nearly always flew inland in a northerly direction. We did not detect an effect of age or weather on departures. The decision by lean birds to reorient movement inland may reflect the suitability of the coastal stopover site for deposition of fuel stores and the motivation to seek food among more extensive forested habitat away from the barrier.