Egyptian vultures from Eastern Europe migrate twice as far as vultures in Western Europe to their wintering grounds in Northern Africa largely to avoid crossing large waterways, which do not have as many reliable thermal currents as routes over land. The largest study of the vultures’ migrations was published in Frontiers in Ecology and Evolution and co-authored by a Smithsonian Migratory Bird Center scientist and other partners.
The study tracked Egyptian vultures across approximately 70% of their range through 44 countries. They found high migratory connectivity between subpopulations but low connectivity within subpopulations across the vulture’s entire wintering range. Since the species is endangered, it is important for scientists to understand what kinds of obstacles they encounter during their migrations to better protect them and the areas where they are spending time.
“This study is an excellent example of scientific collaboration, with input from 11 research projects and 31 organizations,” said Evan Buechley, co-author of the paper and postdoctoral fellow with the Smithsonian Migratory Bird Center. “This enabled us to investigate the ecology of this endangered species across 70% of its global distribution. Our findings illuminate great variation in migratory behavior, including timing, duration, speed, and efficiency of migration, as well as the major overwintering destinations for the species in Africa. This information is vital for understanding potential drivers of population declines, as well as for targeting conservation actions.”
Scientists tracked 94 Egyptian vultures from four different subpopulations over 11 years with lightweight transmitters that weighed less than 3% of their body masses. The vultures were from breeding populations in Western Europe, the Balkans, the Caucasus Mountains and Israel, but all over-winter in Northern Africa. The vultures traveling to Northern Africa from Eastern Europe had longer migration routes and encountered four different bottlenecks, or areas where geography constricted their migrations routes.
They mostly avoided flying directly over large water bodies, including the Mediterranean and Red seas. Vultures traveling from Western Europe had a much more direct and shorter route to Northern Africa. They only encountered one bottleneck at the Strait of Gibraltar.
In addition to revealing differences between the subpopulations, the study also illuminated differences within the subpopulations. When Egyptian vultures made it to their wintering grounds, the Western and Eastern subpopulations’ ranges did not overlap. However, the wintering grounds of birds from the same breeding subpopulations could be spread over distances of as much as 4,000 kilometers. The vultures’ migrations back to Western and Eastern Europe in the spring were longer and slower than the fall migrations to wintering grounds.
Future research could focus on how where and why Egyptian vultures die, both on migration and in breeding and wintering areas, to identify the drivers behind the species’ decline.