Long-Term Shifts in Autumn Migration by Songbirds at a Coastal Eastern North American Stopover Site

Abstract

Abstract We investigated long-term trends in mean autumn capture dates of 19 species of migratory passerines including 11 long-distance migrants and eight short-distance migrants. Birds were captured between 1960 and 2007 at a banding station in southern Rhode Island. We detected annual trends in the highest ranked models with mean capture dates of seven species significantly delayed by an average of 3.0 days per decade; 38% of long-distance migrants and 50% of short-distance migrants studied significantly delayed migration. We found no evidence of long-term shifts in autumn migration timing for seven species and mean capture dates of five species exhibited non-linear annual trends. Mean autumn temperature was an important factor in explaining annual trends for eight species. Changes in annual capture rates for some species may have an equal or greater role than year or temperature in explaining long-term trends in autumn migration timing. Our analysis suggests that some migratory bird species are now dep...