Project Report: November 2006

Cinereous vulture egg evaluation

Cinereous vulture egg piping

Cinereous vulture hatchling

Adult cinereous vulture

Ikh Nart supports a large, dense (nests per unit area) breeding colony of cinereous vultures in the northern part of the reserve. Vultures in Ikh Nart nest primarily on rocky outcrops and the scattered elm trees (Ulmus pumila) in the reserve. Nest site availability appears to constrain breeding to areas with suitable nesting habitat; in this case, the more rugged areas like Ikh Nart. The overall objective of this project is to understand the nesting ecology of cinereous vultures well enough to develop long-term conservation management plans that ensure their long-term health and enjoy enduring public support.

Data were collected on the nesting success of cinereous vultures by monitoring nests from incubation to fledging. 215 vulture nest sites were checked to determine if nests were active nests. A variety of nest characteristics were measured for all vulture nests (active or inactive), including nest height, diameter, cup diameter, and height off the ground; perceived difficulty of entry for ground predators and, for nests on rocks, slope, aspect, and view shed (i.e., the estimated number of degrees a sitting vulture can see). Other data were collected using a GIS, such as distance to other nests, number of nests within 1 km, and distance to other important features, such as water and pastoralist camps.

The fertility of all vulture eggs was assessed using a Buddy 2® Egg Monitor and collected egg measurements (length, width, and weight). The egg monitor provided data on the embryo's heart rate in fertile eggs. After the eggs hatched, half of the nestlings were selected for detailed, periodically monitoring. These nestlings were paired with nestlings that were not monitored to allow us to assess the impact of our actions on nesting success rates. For nestlings that were monitored, nestlings were measured periodically, including total body length (with and without feathers), wing lengths (with and without feathers), leg length (from the top of the femur to the tip of the middle toe), tarsus length, middle toe length, talon length, beak length, and weight. In late July through August as many nestlings as possible were banded with wing tags and leg bands.

Nesting success rates were nearly identical for pairs that located their nests in trees compared with those that placed their nests on rocky outcrops. Lower success rates were expected for pairs that nested in rocky outcrops, as most of these nests are easily accessible by ground (non-avian) predators, such as wolves (Canis lupus), lynx (Lynx lynx), or foxes (Vulpes spp.). Yet, in past years, success rates were lower for pairs that nested in trees and here success rates were the same. Although some tree nests blow over in strong spring dust storms, these are relatively rare events. Why ground predators do not appear to target the seemingly accessible nests on rocky outcrops remains a mystery.

Finally, during July and August 2006 we were extremely successful at measuring and marking vulture chicks. 37 cinereous vulture chicks were captured just prior to fledging for final morphometric measurement collection and permanent identification using aluminum leg bands and vinyl patagial (wing) bands. Combined with previous years' data, the morphometric measurements will enable the construction of an accurate model of vulture chick growth and development from hatching to fledgling. Permanent identification (leg banding and patagial tagging) will provide insight into mortality and dispersal for this species. There is no other cinereous vulture project in the world that is working with this many individuals marked.

The results are already being used for conservation. BirdLife International designated Ikh Nart as an Important Bird Area (IBA) for Mongolia because of the large aggregation of cinereous vulture and lesser kestrel (Falco naumanni) nesting pairs. In addition, the local soum (that manages Ikh Nart) is using our results in their recently drafted management plan for the protected area to ensure adequate protection for nesting sites.