Band recoveries reveal alternative migration strategies in American Robins

Abstract

Abstract Migration strategies may change in response to climate change with consequences for conservation efforts. We used 80 years (1934−2014) of band recovery data (N = 1,057) to describe spatial and temporal patterns in the migration behavior of American Robins. The distribution of recoveries suggests strong continental scale connectivity with distinct separation between eastern and western North America, with a more moderate degree of connectivity within these regions. We also found little evidence of differential migration between males and females. Despite previous studies that suggest the winter distribution of robins has shifted northward, our analysis shows no obvious change in migration distance over time. Surprisingly, we found that a significant proportion of across season band recoveries occurred locally (20%), in close proximity to the original banding locations. It’s well known that large numbers of robins linger in northern breeding grounds well into the winter of some years, but the proximity of these birds to breeding areas was previously unknown. We found little evidence that the winter latitude of migrants or local recoveries shifted over time. However, there was a trend for increased frequency of local recoveries in recent decades, providing an alternative hypothesis for the northward shift in winter distribution.