October 13, 2010
By Corinne Kendall, Princeton University
Ruppell’s Vultures travel almost as much as I do. These enormous birds nest in cliffs rather than trees. Cliffs are great from the standpoint of the chick. They are well protected from predators and the elements, but make a lot of extra work for the parents. Most cliffs in Kenya are very far from protected areas and other places of high wildlife density where the vultures will find most of their food.
As a result, Ruppell’s Vultures have to travel far, flying to and from their feeding grounds and the nest every few days. Since the distances can be more than 100 km (70 miles), it is a good thing the vultures are soaring birds. Soaring flight allows them to travel great distances while using very little energy.
Before we started putting GSM-GPS units on vultures, we knew a little bit about where they nested. In particular, three important cliff-nesting sites in close proximity to Masai Mara National Reserve (where we trapped the vultures) had been identified:
1. The Hell’s Gate cliffs
2. The cliffs near Lake Kwenia, which is not too far from Nairobi
3. The huge cliff faces along Gol Mountains just across the border in Tanzania.
Hell's Gate Vulture
The costs of travel would be different depending on which of these nests a given bird was using and so one might expect birds from different cliff sites to use different foraging grounds and have varied travel paths. By trapping the birds in Mara, we would get a haphazard sampling, which I had hoped would include birds from each of these cliff sites. In the first year we got birds from Lake Kwenia and the Gol Mountains, but given that only a few individuals use the cliffs at Hell’s Gate we didn’t trap a bird using these cliffs. A few days ago, we got some exciting data suggesting that we actually caught a Hell’s Gate bird this year – just take a look at the map of this bird’s movement. He dropped off right in Hell’s Gate, just in time for the evening’s rest.
