BREEDING BIOLOGY OF THE BEARDED VULTURE IN SOUTHERN AFRICA, .1. THE PRELAYING AND INCUBATION PERIODS

In southern Africa the Bearded Vulture Gpaetus barbatus lays its eggs in mid-winter. between the second half of May and the first week of July. Pairs became more active in their nesting areas about six weeks before laying and usually roosted there at night. Courtship flights were less frequent and demonstrative than in Eurasian birds and took place mainly in the late afternoons. During the pre-laying period most nest visits (77%) were to bring nesting material, 92% by the male. All nesting material was arranged by the female. Copulation was always preceded by allopreening, and occurred most frequently in the mornings. No copulation or courtship display took place after the first egg had been laid. Of 18 clutches, 16 (89%) contained two eggs and the remainder one egg. The laying interval was usually 3-5 days (range 2-9 days). Incubation started with the first egg and was evenly shared by both parents during the day, but only the female incubated at night, individual pairs maintained distinctive nest attendance and foraging period timetables, which allowed sufficient time for self-foraging by both parents. No food was brought into the nest during the pre-laying and incubation periods, but in some pairs food was cached in nearby potholes in cliffs. The incubation period was 56-57 days. © 1990 Taylor and Francis Group, LLC.