Copulations Throughout Breeding in a Colonial Accipitrid Vulture

Abstract

In various falconiforms, evidence of a high frequency of copulations as well as their occurrence after egg-laying suggests that the function of this behavior may not be restricted to fertilization (Newton 1979).Also, in apparently monogamous species, most copulations occur between mated partners; however, copulations between individuals that are not paired to each other (extrapair cooulations, EPCs) have been observed in over 20 avian families to hate (I&Kinney et al. 1984).Here I present observations on the associated behavior and frequency of copulations, including EPCs, in a monogamous and colonial accipitrid vulture.STUDY AREA AND METHODS Observations were conducted at a colony of about 55 Cape Vultures (Gyps coprotheres) in a ravine of the Potberg, Cape Province, South Africa.Between May 198 1 and May 1982, I spent 12 days each month (07:OO to 16:30), regardless of weather conditions, observing birds from the side opposite the nesting and roosting cliffs.The concluding activities of the 1980 breeding season, all stages of the 1981 season and the initiation of the 1982 season were covered.Individuals and sexes of these large birds (8 to 10 kg) are visually indistinguishable in the field; however, some breeding birds were recognizable as they had been ringed as nestlings.Ages were estimated using the characters given in Mundy (1982), and sexes were determined by observation of copulation where at least one participant was ringed.With the exception of nest-building, male and female Cape Vultures share duties related to rearing each season' s single offspring, and probably pair-bond for life (Robertson, in press, A. F. BoshofT, pers.comm.).In 198 1, 17 breeding pairs produced 16 eggs (1982: 18 pairs and 17 eggs).