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Journal ArticleDOI

Breeding and food of the bateleur in zimbabwe (rhodesia)

01 Sep 1980-Ostrich (Taylor & Francis Group)-Vol. 51, Iss: 3, pp 168-178
TL;DR: Three nesting territories of Bateleurs Terathopius ecaudatus were studied at Essexvale, Zimbabwe, from 1962 to 1976, and this paper augments previously published observations.
Abstract: Summary Steyn, P. 1980. Breeding and food of the Bateleur in Zimbabwe (Rhodesia). Ostrich 51:168-178 Three nesting territories of Bateleurs Terathopius ecaudatus were studied at Essexvale, Zimbabwe, from 1962 to 1976, and this paper augments previously published observations. Further details of breeding biology are given, and these show close similarities to those of snake eagles Circaetus spp. In 22 pair-years at Essexvale 17 young were reared, or 0,77 young/pair/year, and if combined with five years' observation at another nest in Zimbabwe then the figure is 0,81. A total of 238 prey items was collected, 47,5% birds, 42,0% mammals, 8,0% reptiles and 2,5% fish, and comparisons are made with three other studies of Bateleur prey. Evidence for direct predation is considered; Bateleurs kill many species of birds and a variety of mammals, but reptiles are not a significant aspect of diet. Carrion appears to be most important in the diet of immatures. The Bateleur has undergone a serious decline in South Afric...
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Journal ArticleDOI
TL;DR: In this article, the authors compared trends between the ungulate migration and non-migration season among three land use types (reserve, buffer, and grazed) and among the species surveyed to establish the causes of declines in scavenging raptors.

158 citations

Journal ArticleDOI
TL;DR: In this paper, the importance of shrubs as habitat structures at three spatial scales for yellow mongooses (Cynictis penicillata) was analyzed in the southern Kalahari rangelands.
Abstract: Shrub encroachment as a result of heavy grazing is assumed to affect species diversity negatively. However, shrubs may be important for animals because they provide shelter and nesting sites. In this study we analyzed the importance of shrubs as habitat structures at 3 spatial scales for yellow mongooses (Cynictis penicillata )i n southern Kalahari rangelands. At burrow location we assumed shrubs reduce predation risk for occupants of burrows under shrubs and that shrubs protect burrows from trampling by larger herbivores. To investigate this, at microhabitat scale, we recorded the location of 24 reproductive and 112 sheltering burrows. However, in shrubencroached areas prey availability is low. We surveyed vegetation cover and the spatial distribution of shrubs at mesoscale (1 ha) and compared it to random surveys. Group size and reproductive success were determined for 18 groups and related to shrub cover at territory scale (macroscale, 250 ha). Our results show that yellow mongooses prefer reproductive burrows under large Acacia shrubs if the distance to the next shrub was greater than 10 m. At mesoscale, areas with lower vegetation cover were favored. Shrub encroachment at territory scale (macroscale) affected group size negatively. A range of shrub cover between 15% and 17.5% indicates a critical upper threshold limiting reproduction. For yellow mongooses territory selection represents a trade-off between abundance of suitable shrubs for burrows (protection service) and the proportion of shrub cover at large spatial scales (reduced prey availability).

25 citations

Journal ArticleDOI
TL;DR: It is shown that theropods between 27 and 1,044 kg would have gained a significant energetic advantage over individuals at both the small and large extremes of theropod body mass through their scavenging efficiency.
Abstract: Theropod dinosaurs dominated Earth’s terrestrial ecosystem as a diverse group of predators for more than 160 million years, yet little is known about their foraging ecology. Maintaining a balanced energy budget presented a major challenge for therapods, which ranged from the chicken‐sized Microraptor up to the whale‐sized Giganotosaurus, in the face of intense competition and the demands of ontogenetic growth. Facultative scavenging, a behavior present in almost all modern predators, may have been important in supplementing energetically expensive lifestyles. By using agent‐based models based on the allometric relationship between size and foraging behaviors, we show that theropods between 27 and 1,044 kg would have gained a significant energetic advantage over individuals at both the small and large extremes of theropod body mass through their scavenging efficiency. These results were robust to rate of competition, primary productivity, and detection distance. Our models demonstrate the potential...

20 citations


Cites background from "Breeding and food of the bateleur i..."

  • ...This allometry would have important consequences in niche partitioning among theropod species but also within species during ontogeny, as is seen across a diversity of extant animals (Steyn 1980; Winemiller 1989; Hirai 2002; Woodward and Hildrew 2002; Platt et al. 2006; Knoff et al. 2008)....

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  • ...In particular, many of the niches in these systems were divided across ontogeny, with extreme disparities between adult and juvenile body sizes (Steyn 1980; Winemiller 1989; Brusatte et al. 2010; Myhrvold 2013)....

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Journal ArticleDOI
01 Sep 2002-Ostrich
TL;DR: In this article, a subjective assessment was made of the road mortality suffered by each species of nightjar in the Afrotropics and the results showed that road kills were the major mortality factor affecting most adult nightjars.
Abstract: Afrotropical nightjars have evolved a number of adaptations that enable them to cope well with various natural mortality factors facing them. They are, however, extremely vulnerable to the many human factors that affect their lives. Three areas of human activity are of major concern: road traffic, habitat destruction and food gathering. Suitable legislation, with strict enforcement, should ensure that nightjar populations are not harvested excessively for the table. The many National Parks, Game Reserves and other protected areas throughout the Afrotropics should ensure that sufficient breeding and feeding habitats are available for the various nightjar species. There does not appear to be a solution to the road traffic problem, so road kills will almost certainly be the major mortality factor affecting most adult nightjars. A subjective assessment was made of the road mortality suffered by each species. The forest species (Brown Nightjar, Veles binotatus, Bates's Nightjar, Caprimulgus batesi and Prigogin...

20 citations

Journal ArticleDOI
01 Dec 1996-Ostrich
TL;DR: Herholdt, JJ, Kemp, AC & Du Plessis, D 1996 Aspects of the breeding status and ecology of the Bateleur and Tawny Eagle in the Kalahari Gemsbok National Park Ostrich 67:126-137 The nesting s
Abstract: Herholdt, JJ, Kemp, AC & Du Plessis, D 1996 Aspects of the breeding status and ecology of the Bateleur and Tawny Eagle in the Kalahari Gemsbok National Park Ostrich 67:126-137 The nesting s

10 citations

References
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Journal ArticleDOI
01 Dec 1977-Ostrich
TL;DR: There was no significant difference between the mean reproductive success of five African eagle species that lay two eggs and that of fiveAfrican eagle species laying one egg, even excluding inequalities due to sample size, and other factors.
Abstract: Summary Brown, L. H., Gargett, V. & Steyn, P. 1977. Breeding success in some African Eagles related to theories about sibling aggression and its effects. Ostrich 48:65-71. Previous explanations for fatal inter-sibling strife in eagles (lack of food, extra aggressiveness which enhances survival, and an expression of the innate aggressiveness or territoriality of raptors) can not be supported by recent evidence. The latest theory, that the second egg acts as a “reserve”, is examined. If so, eagles normally laying two eggs should have better reproductive success than eagles laying a single egg. However there was no significant difference between the mean reproductive success of five African eagle species that lay two eggs and that of five African eagle species laying one egg. Even excluding inequalities due to sample size, and other factors, the overall finding is the same. In Verreaux's Eagle Aquila verreauxi for which the largest number of records is available there was a significantly higher total loss in...

36 citations