Rare case of an adult male Montagu鈥檚 Harrier Emphasis Type='Italic'>Circus pygargus/Emphasis> over-summering in West Africa, as revealed by GPS tracking

摘要

Heading>Abstract/Heading> Para ID="Par1">Over-summering within or near the African wintering range by immature, non-breeding individuals occurs regularly in several species of long-distance migratory raptors, yet the extent of over-summering in Africa by adult birds remains unclear. In this study, we describe a case of an adult Montagu鈥檚 Harrier over-summering in Africa, as revealed by GPS tracking. By relating detailed knowledge of the bird鈥檚 movements to remotely sensed environmental data (normalized difference vegetation index, NDVI), we show that over-summering in this case was likely related to an exceptionally difficult breeding season the previous year rather than an effect of adverse weather conditions encountered during the winter or a failed attempt to migrate. Various factors are discussed as potential driving forces behind the bird鈥檚 intra-African movements. Finally, we relate the documented case to a large number of North European Montagu鈥檚 Harriers studied by telemetry and show that over-summering in Africa by adult individuals is indeed a rare event./Para>