Neotropical Bird Migration during the Ice Ages: Orientation and Ecology

ABsTRAcr.-Reconstruction of breeding habitat of North American Neotropical migrants 18,000 years ago and 9,000 years ago indicated major shifts in both location and composition of plant communities relative to present conditions. Increased vegetation in xeric areas may have compensated, at least in part, for the reduction in breeding habitat due to glaciation. Autumnal flights of Neotropical passerine migrants flying on constant headings from North America to Central and South America were simulated under present wind conditions and for winds during periods of glaciation at 18,000 and 9,000 years ago. The 1550 average headings currently observed for Atlantic migrants were found to function well during periods of glaciation and may have been more generally useful during those times than at present. Received 15 June 1994, accepted 27 January 1995.