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Journal ArticleDOI

The Breeding Biology of Aquila verreauxi Lesson.–Part I.

03 Apr 2008-Ibis (Blackwell Publishing Ltd)-Vol. 89, Iss: 3, pp 387-410
About: This article is published in Ibis.The article was published on 2008-04-03. It has received 12 citations till now.
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Journal ArticleDOI
01 Jun 1978-Ostrich
TL;DR: Comparisons are made between Matopos and Tanganyika observations on Black Eagles and between observations on sibling aggression in the Lesser Spotted Eagle Aquila pomarina where the second hatched chick lives longer and does not die directly from attack.
Abstract: Gargett, V. 1978. Sibling aggression in the Black Eagle in the Matopos, Rhodesia. Ostrich 49:57-63. A two-egg clutch of the Black Eagle Aquila verreauxii was observed from the hatching of the first...

56 citations

Journal ArticleDOI
03 Apr 2008-Ibis
TL;DR: The species of eagles occurring in Embu district are detailed, with general notes on the methods and scope of the study, and the inter-relations of the various species are discussed from the points of view of territorial agressiveness and competition for prey.
Abstract: SUMMARY. 1 The species of eagles occurring in Embu district are detailed, with general notes on the methods and scope of the study. 2 The vegetation and climate of Embu district are described, and their effect upon eagles is discussed. 3 Population and inter-relations. The actual population of eagles and of the Secretary Bird in an area of approximately 146 sq. miles is given and their remarkable local concentrations are described. The inter-relations of the various species are discussed from the points of view of territorial agressiveness and competition for prey. 4 Detailed accounts are given of the breeding biology of Sagittarius serpentarius, Aquila verreauxi, A. wahlbergi, Hieraaetus spilogaster, Polmaetus bellicosus, Stephano-aetus coronatus and Circaetus cinereus, and some information for Terathopius ecaudatus, Circaetus pectoralis, and Aquila rapax, Hieraaetus ayresi, Lophaetus occipitalis, and Cuncuma vocifer. The headings for each species include: “Nests and nest-building”, “Incubation period”, “Fledging period” (with special attention to food), and “Post-fledging period”. 5 The following special aspects of breeding behaviour are described and discussed: (1) Display, (2) Use of green branches, (3) Breeding seasons, (4) Breeding success, (5) Breeding frequency.

39 citations

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

Journal ArticleDOI
TL;DR: Alarm calls in White-tailed Hawks are given in the context of potential danger such as when their territory has been intruded by mate or food competitors, nest predators, or humans.
Abstract: Although variation in bird vocalizations is well-studied (Marler 1960, Beer 1970, Jellis 1977, Falls 1982, Brown and Farabaugh 1991), few falconiforms have been intensively examined. The White-tailed Hawk (Buteo albicaudatus), however, exhibits remarkable patterns of intersexual as well as individual variation (Farquhar 1986) not previously identified in this species (Brandt in Bent 1937, Stevenson and Meitzen 1946, Slud 1964, Snyder and Snyder 1991). Hereafter referred to as alarm calls in White-tailed Hawks, these loud vocalizations are given in the context of potential danger such as when their territory has been intruded by mate or food competitors, nest predators, or humans. In Falconiformes, alarm calls (also known as territorial calls) gen-

32 citations

Journal ArticleDOI
01 Mar 1975-Ostrich
TL;DR: Territory size was not constant, the largest territories had the greatest area of open grassland probably in order to encompass a sufficient koppie area, and Territory shape in the airspace appeared to be ...
Abstract: Summary Gargeit, V. 1975. The spacing of Black Eagles in the Matopos, Rhodesia. Ostrich 46:1-44. Ten adjacent pairs of Black Eagles Aquila verreauxi in the high density population in the Matopos were studied from September 1970 to the end of April 1973. 1 458 hours were spent observing the behaviour of all Black Eagles in the area encompassed by the study pairs and some of their neighbours. All perches were plotted and all flights recorded. Ground level boundaries were estimated; common boundaries were fixed at half the distance between neighbours' low level flights. Territory size was calculated and a habitat division made between open areas and koppie areas (rocky outcrops). The latter were where the eagles main prey, hyrax Procavidae, lived and were seen. Territory size was not constant, the largest territories had the greatest area of open grassland probably in order to encompass a sufficient koppie area. Koppie areas varied less in size than open areas. Territory shape in the airspace appeared to be ...

31 citations