Directional shifts in migration pattern of rollers (Coracias garrulus) from a western European population

Abstract

Individual migrants often fly detours when travelling between breeding and non-breeding sites, resulting in specific changes in flight directions along a migratory leg. Western European populations of the European Roller (Coracias garrulus), the only member of the roller family of birds to breed in Europe, differ substantially in their predicted flight directions, leading to different hypotheses being suggested for passage areas and non-breeding destinations. In this study we have tested the hypotheses on a western or eastern detour and different crossings of the Sahara desert by tracking European Rollers breeding in southern France using light-level geolocators. After the departure from the breeding site between mid and end July, the three European Rollers which were tracked crossed the Mediterranean and the Sahara desert heading in straight southern direction. When arriving in the Sahelian zone they abruptly changed their direction eastwards to circumvent the Gulf of Guinea and reached the western Lake Chad basin, where they made a final direction shift to reach the non-breeding sites in western Angola. Our findings support the hypothesis of a straight north–south Sahara crossing with subsequent directional shifts. Whether western Africa serves as the non-breeding residence of European Rollers from the Iberian Peninsula and northern Africa remains to be elucidated.