Changing migration patterns of the Short-eared Owl Asio flammeus in Europe: an analysis of ringing recoveries

Abstract

Analysis of ring recovery data for Short-eared Owls Asio flammeus spanning 96 years, 1912–2007, identified spatial and temporal differences in migration patterns. Birds with breeding areas or natal origins in the Boreal (principally Fenno-Scandinavia) and Continental (principally central Europe) regions tended to move the greatest distances. Although birds from the North Sea littoral and Britain tended to move shorter distances, recoveries included far eastern Europe (Russia), the Mediterranean and North Africa. Recovery distances showed a marked quadratic relationship with time, generally increasing through to the 1960s and 1970s and then subsequently declining, with the apparent turning point being latest for birds from the Boreal region and upland Britain (areas that retain the strongest populations). Temporal changes in recovery distances appear to be positively related to breeding population density (at least in some areas), but vagaries associated with knowledge of the past and current status of Short-eared Owls in many areas adds difficulty to assessing the validity of such an association. Movements of birds between different breeding seasons suggests considerable potential for connectivity between areas; however, a tendency for reducing distances for such movements since the mid-twentieth century might limit the viability of some ‘populations’ in more southern and fragmented parts of their range.