C. J. Brown

Bio: C. J. Brown is an academic researcher. The author has contributed to research in topics: Gyps coprotheres. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Food requirements and the timing of breeding of a cape vulture colony

Abstract: Summary Komen, J. & Brown, C.J. 1993. Food requirements and the timing of breeding of a Cape Vulture colony. Ostrich 64:86-92. Annual food requirements of a Cape Vulture Gyps coprotheres family, comprising one nestling and two adult birds, and a breeding colony were estimated. A family required 226,1 kg meat during a nestling period of 136 days, and 524,4 kg annually. The greatest family food requirements (average 1,98 kg/day) occurred between 60 and 100 days after hatching. The period between 60 and 100 days after hatching was the most critical period of food demands, because (a) this was the period of greatest nestling food requirements, (b) only one parent could be away from the nest at a time, and (c) daily family food intake was effectively constant due to temporal constraints on foraging. The estimated food requirements of a breeding colony comprising 152 breeding pairs and 98 nonbreeding birds was 89 388 kg meat annually, and 36 892 kg during the nestling period, with the highest food requirements ...

Competitive behaviour and feeding rate in a reintroduced population of Griffon Vultures Gyps fulvus

Abstract: Intraspecific competitive behaviours were studied in a reintroduced population of Griffon Vultures Gyps fulvus in order to describe the pattern of competition between ages and sexes, assess the effect of reintroduction on competitive behaviour, and study the potential consequences of food management on competition. There was no evidence for a difference in feeding or display rates between age classes. However interaction rates, aggressiveness and dominance were higher in old adults than in the other age classes. No difference in the pattern of competition was found between sexes. There was no difference in the competitive ability (feeding rate and dominance) of reintroduced and wild-bred individuals. Feeding rates increased with resource availability. Group size also increased with food mass, but was lower than the theoretical maximum number of birds. This may be evidence of competition by interference where some individuals are able to increase their feeding rate by the exclusion of others. An increase in both the number of carcasses and the number of feeding sites is thus recommended to induce dispersal and reduce this competition.

Breeding behaviour and parental care in the Griffon Vulture Gyps fulvus on the island of Crete (Greece)

Abstract: A field study of the breeding behaviour of griffon vultures (Gyps fulvus) was conducted in Crete (Greece) during 1997–2000. The main behavioural patterns examined were aerial displays, nest defence, copulation, nest building, brooding and food provisioning to the chicks. The nesting territory consisted of a semicircle ca 5 m radius around the nest that was defended against conspecifics. Copulation attempts mainly occurred in the nesting ledge with a success rate of 77%. On average every pair accomplished 0.16 ± 0.34 copulations per day (range = 0–4) while 3.3% of the total attempts accounted for extra–pair copulations. Supplying material to the nest started 32 ± 9 days prior to egg laying (range = 17–44) at a rate of 5 ± 3.52 bouts/pair/day (range = 1–14).The mean number of items added to the eyrie was 2 ± 1.3/bout/pair (range = 1–8) with 63.5% of these being soft greenery.The mean frequency of relief at the nest relieves was 0.5 ± 0.64 bouts/pair/day (range = 0–2) while an incubation shift lasted on aver...

Breeding data on the birds of Namibia: laying months, colony and clutch sizes and egg measurements

Abstract: The timing of bird breeding in Namibia and the sizes of clutches and nesting colonies are presented per species, derived from 7 231 nest record cards, over 300 publications, museum and private egg collections and via personal communications.

Long-term data indicates that supplementary food enhances the number of breeding pairs in a Cape Vulture Gyps coprotheres colony

Abstract: The number of vultures is declining in many parts of the world due to numerous threats, such as poisoning and collisions with power-lines as well as the lack of adequate food sources. Vulture restaurants, i.e. supplementary feeding stations, have become a widespread conservation tool aimed at supporting vulture colonies. However, it is poorly understood how vulture restaurants influence population dynamics and whether they affect breeding success of vulture populations. We used a 12-year dataset from a breeding colony of the Cape Vulture Gyps coprotheres and a nearby vulture restaurant in South Africa to investigate the effect of supplementary food on population dynamics and breeding success. We found a significantly positive effect of supplementary food during the nest-building stage on the number of breeding pairs. However, breeding success, i.e. the proportion of successful nests, did not depend on supplementary food during the incubation and rearing stage. Especially during the critical rearing stage, the amount of food supplied might not have been sufficient to meet food demands of the colony. Still, our results indicate that carefully managed vulture restaurants might stabilise vulture colonies and can therefore aid vulture conservation.

Understanding continent-wide variation in vulture ranging behavior to assess feasibility of Vulture Safe Zones in Africa: Challenges and possibilities

Abstract: Protected areas are intended as tools in reducing threats to wildlife and preserving habitat for their long-term population persistence. Studies on ranging behavior provide insight into the utility of protected areas. Vultures are one of the fastest declining groups of birds globally and are popular subjects for telemetry studies, but continent-wide studies are lacking. To address how vultures use space and identify the areas and location of possible vulture safe zones, we assess home range size and their overlap with protected areas by species, age, breeding status, season, and region using a large continent-wide telemetry datasets that includes 163 individuals of three species of threatened Gyps vulture. Immature vultures of all three species had larger home ranges and used a greater area outside of protected areas than breeding and non-breeding adults. Cape vultures had the smallest home range sizes and the lowest level of overlap with protected areas. Rüppell's vultures had larger home range sizes in the wet season, when poisoning may increase due to human-carnivore conflict. Overall, our study suggests challenges for the creation of Vulture Safe Zones to protect African vultures. At a minimum, areas of 24,000 km 2 would be needed to protect the entire range of an adult African White-backed vulture and areas of more than 75,000 km 2 for wider-ranging Rüppell's vultures. Vulture Safe Zones in Africa would generally need to be larger than existing protected areas, which would require widespread conservation activities outside of protected areas to be successful.