摘要:

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 EagleAquila verreauxifor which the largest number of records is available there was a significantly higher total loss in clutches recorded as c/l than in c/2 clutches, but the reasons for the laying of a one-egg clutch, and its success or failure, have not been investigated. In three out of 120 c/2 the second-laid egg acted as a “reserve”, but in 110 cases the second-laid egg was “wasted”. Direct evidence and a comparison of reproductive success between two-egg and one-egg African eagles does not support the latest theory, therefore inter-sibling strife which effectively reduces the clutch of two to one, is still inexplicable.

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634083

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Mundy. P. J. & Cook, A. W. 1977. Observations on the breeding of the Pied Crow and Great Spotted Cuckoo in northern Nigeria. Ostrich 48:72-84.

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634084

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Summers, R. W., Cooper, J. & Pringle, J. S. 1970. Distribution and numbers of coastal waders (Charadrii) in the southwestern Cape, South Africa, summer 1975–76.Ostrich48: 85–97. A survey of the distribution and numbers of waders (suborder Charadrii) in the coastal regions of the southwestern Cape was conducted from November 1975 to February 1976. Forty-four coastal wetlands and 49 sections of coastline were visited between the Olifants and Groot-Brak rivers. The estimated total wader population was 119 008 of which 102 841 (86,4%) were Palaearctic migrants. Langebaan Lagoon and the Berg estuary supported the largest numbers. The Curlew SandpiperCalidris ferrugineaand SanderlingCalidris albawere the most numerous species. The abundance of waders was greater on west coast shores than along the south coast.

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634085

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Pringle, J. S. & Cooper, J. 1977. Wader populations (Charadrii) of the marine littoral of the Cape Peninsula, South Africa. Ostrich 48: 98–105.

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634086

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Vernon, C. J. 1977. Nineteenth ringing report for southern Africa.Ostrich48:106-109. A report on ringing activities for southern Africa from July 1975 to June 1976 is presented. A total of 36 016 birds of 419 species was ringed. The trends follow the general decline in ringing activities sinze a peak in 1970/71.

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634087

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634088

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634089

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634090

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634091

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0030-6525    

DOI:10.1080/00306525.1977.9634092

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor