Ranging behaviour of an adult female greater spotted eagle (Clanga clanga) wintering in Sudan for 10 years, as revealed by satellite telemetry

Using global position system (GPS) technology, we tracked an adult female greater spotted eagle (Clanga clanga) on its wintering grounds in the Sudan-South Sudan borderland during 2005–2015. There were 10 909 GPS locations for this bird in the non-breeding range. Throughout the study, the eagle showed fidelity to its wintering grounds. The non-breeding season coincided with the dry season. The median arrival date was 11 October (n = 10). The median departure date (n = 10) was 4 March, and was less variable than the arrival date. The 95% kernel density estimate (KDE) for all years was 33 838 km2, and the 50% KDE encompassed 6 585 km2. The wintering range was split between two areas, west and east, with the eagle typically arriving in the western area, where it stayed for some time. It then moved about 330 km to the eastern area, where it would remain for a few weeks before departing for Europe in the spring. In both the western and eastern subareas, the annual home ranges overlapped to a variable extent (14–99%). The high degree of fidelity to the wintering grounds shown by this bird was mirrored by the behaviours of two other adult greater spotted eagles that we tracked (using >1 tracking devices) for 15 years that wintered in South Sudan and Turkey. The number of greater spotted eagles that winter in Africa is a matter of speculation, although virtually all individuals are likely to pass through a narrow corridor near Suez, Egypt. Collectively, these tracking data and the findings of other studies suggest that greater spotted eagles from the western parts of the European breeding range often move to Africa. Further, the Sudd wetlands in South Sudan are important for greater spotted eagles and other rare bird species during the non-breeding season.