A change in the breeding season of Rüppell's Griffon Vultures Gyps rueppellii in the Serengeti in response to changes in ungulate populations

Breeding by Rüppell's Griffon Vultures Gyps rueppellii is synchronized but the time of breeding of colonies in the Serengeti region of Tanzania has changed by 5 months over the period between 1969–1970 and 1985. During this interval there have been considerable changes in the ungulate populations within the feeding range of the vultures, resulting in an increase to the food supply available to the birds. It is suggested that this species may have two alternative breeding seasons, the selective value of each depending on the magnitude of the food supply.