The feeding ecology of cape vultures Gyps coprotheres in a stock-farming area

Department of Zoology, University of the Witwatersrand, Johannesburg, South Africa
Biological Conservation (Impact Factor: 4.04). 01/1986; 35(1):63-86. DOI: 10.1016/0006-3207(86)90027-3

ABSTRACT Cape vultures Gyps coprotheres in the southwestern Cape Province feed exclusively on sheep carcasses, within a limited foraging area. The size and shape of the foraging range was determined by means of a postal survey and confirmed by a radio-tracking study. The quantity of food available within the range, while seasonally variable, was estimated to exceed the colony's requirements. Data pertaining to daily feeding forays of individuals, monthly foraging patterns of the colony and the growth of nestlings indicated no seasonal shortages in the amount of food obtained. The colony remains susceptible to the effects of poisons used in the area; levels of contaminants recorded in most eggs are considered low.

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    • "Accurate estimates of their population can be made by conducting surveys in these sites during certain months of the year and times of the day [5]. As a result, improved monitoring techniques consist of counting birds at their breeding or roosting sites early in the morning or late in the evening before or after their daily foraging trips [6]. The common black kite is an accipitrid and is widely distributed in the old World [7]. "
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    ABSTRACT: Birds of prey had a large home range and inhabit areas which are far away from human access so it is difficult to estimate their population. Kites (Milvus migrans) and crows (Corvus splendens) often gather in large communal roosts during migration at a site for food and breeding. The present study was done to estimate their population by Roost Count Method. Four sites were visited and population of kites and crows was estimated. It was found that 356 kites and 224 crows were present on an average at any roost. The soaring kites in the high skies and crows in the forenoon and afternoon sessions were more or less absent. In addition, these birds were less common on huge Garbage sites. Shockingly, it seems that like vultures, black kites and crows are on their way to elimination in Lahore.
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    • "This difference is due to the weather conditions and the farming practices near its colonies. Birds feed largely on resident livestock producing the highest dead biomass during winter (Robertson & Boshoff 1986, Mundy et al. 1992, Scott et al. 2000). Meanwhile, suitable flying conditions (SE winds) prevail in summer allowing the vultures to depart early in the morning (Boshoff et al. 1984). "
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    ABSTRACT: We studied the foraging behaviour of Eurasian griffonsGyps fulvuson the island of Crete during 1997-2005 by direct observations in four colonies and by monitoring the movements of seven radio-equipped individuals. The estimated foraging range of griffon colonies, based on direct observations, ranged from 206-851 km2 by using the Minimum Convex Polygon method, and 195-527 km2 by using the Adaptive Kernel method, with corresponding means of 472 and 380 km2, respectively. Meanwhile, radio-tracking showed that foraging vultures covered an area ranging from 390-1300 km2. The mean foraging radius was calculated at ca 15 km and the mean maximum one at 29.9 km. On windless days, griffons’ mean cross-country speed was 5.1 m/second (maximum=13.3 m/second), with a mean climbing rate of 0.6 m/second and a mean inter-thermal gliding speed of 18.8 m/second. Any livestock car-rion located up to 9 km from a colony was exploited by its members with minimum competition from individuals of adjacent areas. In total, we recorded 23 feeding incidences which took place at a mean distance of 8.4 km from the colonies. The food types identified were sheep carcasses located near stock-farms and offal disposed in waste dumps in the vicinity of the colonies. On average, the griffons allocated 7.6 hour/day to food searching. This varied sig-nificantly between months and seasons. The shortest foraging time was recorded in December (6.4 hour/day) and the longest in June (9.3 hour/day). A significant difference of one hour after sunrise was detected in the departure time from the colony between seasons revealing that griffons departed earlier during winter trying to maintain their foraging budget within the available daytime limits.
    Wildlife Biology 03/2009; 15:37-52. DOI:10.2981/07-090 · 1.07 Impact Factor
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    • "These levels are less than the values reported in eggs of African white-backed vulture (0.05–0.1 lg/g), and higher than the values reported in eggs of two breeding colonies of Cape griffon vulture (0.002–0.09 lg/g) in South Africa during 1981–1982 (Robertson and Boshoff 1986). Further the recorded levels are lower than the threshold level of 0.5 lg/g (Castillo et al. 1994), and also less than the levels which had impaired reproductive success in pelican (King et al. 1985). "
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    ABSTRACT: Organochlorine pesticide residues were determined in tissues of five Indian white-backed vultures and two of their eggs collected from different locations in India. All the samples had varying levels of residues. p,p'-DDE ranged between 0.002 microg/g in muscle of vulture from Mudumali and 7.30 microg/g in liver of vulture from Delhi. Relatively higher levels of p,p'-DDT and its metabolites were documented in the bird from Delhi than other places. Dieldrin was 0.003 and 0.015 microg/g while p,p'-DDE was 2.46 and 3.26 microg/g in egg one and two respectively. Dieldrin appeared to be lower than the threshold level of 0.5 microg/g. p,p'-DDE exceeded the levels reported to have created toxic effects in eggs of other wild birds. Although varying levels of DDT, HCH, dieldrin, heptachlor epoxide and endosulfan residues were detected in the vulture tissues, they do not appear to be responsible for the present status of population in India.
    Bulletin of Environmental Contamination and Toxicology 10/2008; 81(6):561-5. DOI:10.1007/s00128-008-9529-z · 1.22 Impact Factor
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