Orientation of native versus translocated juvenile Lesser Spotted Eagles (Clanga pomarina) on the first autumn migration

The ontogeny of migration routines used by wild birds remains unresolved. Here we investigated the migratory orientation of juvenile lesser spotted eagles (LSE) (Clanga pomarina) based on translocation and satellite tracking. Between 2004 and 2016, 85 second-hatched juveniles (Abels) were reared in captivity for release into the declining German population, including 50 birds that were translocated 940 km from Latvia. In 2009, we tracked 12 translocated juveniles, as well as 8 native juveniles and 9 native adults, to determine how inexperienced birds come to use strategic migration routes. Native juveniles departed around the same time as the adults and 6 of 8 used the eastern flyway around the Mediterranean, which was used by all adults. In contrast, translocated juveniles departed on average 6 days before native LSEs, and 5 traveled southward and died in the central Mediterranean region. Consequently fewer translocated juveniles (4/12) than native juveniles (7/8) reached Africa. We co...