Severe declines of Eastern Imperial Eagle Aquila heliaca populations in the Baikal region, Russia: a modern and historical perspective

The Eastern Imperial Eagle (Aquila heliaca), a vulnerable and declining species, is widely but sparsely distributed throughout its range. Because much of that range extends through the Russian-speaking world, relatively little on the species has been published in English. The world’s easternmost population of Eastern Imperial Eagles, at Lake Baikal, Russia, is particularly well studied and, because of recent rapid population declines, is of great conservation concern. Here, using a data set covering more than 20 years evaluated in the context of historical accounts published in Russian, we assess recent severe declines in this population and the subsequent changes in its conservation status. In intensively surveyed areas near Lake Baikal, numbers of territories occupied by eagles have declined by 80–100 % in the past 20–40 years. Likewise, throughout the entire region, the average number of known occupied and breeding territories were both more than 40 % lower in 1998–1999 than they were in 1982–1983. These data suggest severe long-term declines in the population of Baikal’s Imperial Eagles. Because we observed only limited decreases in reproductive output, our interpretation of the patterns in these data is that mortality of non-breeding birds (wintering adults and all pre-adults) is the most likely cause for this decline. Addressing the causes of this decline is critical to protect this severely threatened population from extirpation