Influence of Heredity on the Location of Wintering Sites, but Not on Migration Routes of Juvenile Imperial Eagles (Aquila heliaca) from the Population of the Volga Region

Data on the migration routes and wintering sites were collected from nine juveniles and one adult imperial eagle (Aquila heliaca). Six of thetagged birds were in family relationships: two siblings, one adult bird and its chick, and two birds born a year apart. The onset of the autumn migration appeared to be the same for all birds, and it started at the end of September to early October. The second migration turned out to be shorter than the first one for all immature eagles. This was because they flew using more direct routes to their previous wintering sites and because some of them had ended their second migration before they arrived atthe first wintering sites. Both siblings had different migration routes, but wintered in the same region. The adult bird and its eaglet started migrating separately, but had the same routes and wintering sites. Both birds born a year apart had the longest routes and reached the southern part of the Arabian Peninsula. The oldest eagle flew across the Bab El Mandeb Strait and spent the winter in the Ethiopian Highlands. The youngest eagle reached an island located in the strait, but then turned back. The coinciding wintering sites, albeit using different migration routes, by related birds seems to prove that the wintering locations, but not the migration routes, are genetically determined in the Imperial Eagles from the Volga region population.