SUPPLEMENTARY OBSERVATIONS ON THE BREEDING BIOLOGY OF THE BOOTED EAGLE IN SOUTHERN AFRICA

Steyn, P. & Grobler, J. H. 1985. Supplementary observations on the breeding biology of the Booted Eagle in Southern Africa. Ostrich 56:151-156

Further observations on the biology of the Booted Eagle Hieraaetus pennatus in southern Africa are presented. Several nest sites in trees are described, and details of behaviour during the incubation and early nestling period are given. The down colour of nestlings is discussed. One juvenile returned to its natal area the following breeding season. In ninepair-years the replacement rate was 1,0 young/pair/year. Prey records confirm that birds predominate. The implications of the recent discovery of breeding in mid-winter in Namibia are discussed; there may be three Booted Eagle populations in southern Africa.     

BIOGEOGRAPHICAL AND TOPOGRAPHICAL VARIATION IN THE PREY OF THE BLACK EAGLE IN THE CAPE PROVINCE,SOUTH AFRICA

Boshoff, A.F., Palmer, N.G., Avery, G., Davies, R.A.G. & Jarvis, M.J.F. 1991. Biogeoraphical and toporaphical variation in the prey of the Black Eagle in the Cape Province, South Africa. Ostrich 62: 58–72.

Prey remains collected at or near Black Eagle Aquilu verreauxii nest sites in the Cape Province, South Africa, were analysed according to frequency of occurrence of prey scies in the samples. A total of 5748 prey individuals, collected from 73 sites, was analysed according to tree biome groups and four nest site types. The Rock Hyrax Procuvia capensis is the dominant prey species, but the eagles' diet sctrum vanestypes. The according to its availability. Indices of species richness and diversity of the prey are inverser correlated with the proportion of the prey contributed by P. capenis, which in turn is determined by topography and vegetation. Biome has a greater influence on the indices than has nest site type. The age structure of the P. capensis prey remains closely reflects the juvenile: sub- adult: adult ratios in the biomes and at the nest site tpes. hfedium-sized (aprox. 1–4,5 kg) pre is usually taken. Juvenile domestic small-stock (lambs ani goat kids) comprised onb 3,4% of the over, total.     

ASPECTS OF THE BREEDING STATUS AND ECOLOGY OF THE BATELEUR AND TAWNY EAGLE IN THE KALAHARI GEMSBOK NATIONAL PARK,SOUTH AFRICA

Herholdt, J.J., Kemp, A.C. & 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 success at 13 nesting territories of Bateleur Terathopius ecaudatus and 19 nesting territorites of Tawny Eagle Aquila rapax was monitored for seven successive years (1988–1994) in a protected area in the Kalahari desert of South Africa. On average Bateleurs laid one year in two (51/95 pair-years) and fledged 0.33 young/pair/year (31/95). Tawny Eagles laid, on average, in two out of three years (66/105), and fledged 0.4 young/pair/year (42/105). Most Bateleurs laid eggs in January and February, while Tawny Eagles mostly laid from May to June. Almost all Bateleur and Tawny Eagle nesting territories located were in the Acacia erioloba savanna in the dry Auob and Nossob riverbeds. Bateleur nesting territories were spaced at intervals of 7.2 km (2.5–14.6 km; n = 9) along the Nossob River. Tawny Eagle nesting territories were spaced at intervals of 17.6 km (6.1–32.7 km) in the Nossob River and 11.3 km (8–14 km) in the Auob River respectively. A total of 13 Bateleur and 30–40 Tawny Eagle nesting territories (27 known active nesting territories) respectively occurred in the Kalahari Gemsbok National Park during the study period. There was evidence of a 13% decline in active nesting territories of Bateleur during the seven year study, and at least a 40% decline over the previous 10 years. Vacated nesting territories were not reoccupied. There was no safe buffer zone around the Kalahari Gemsbok National Park and persecution in the adjacent farmlands, when foraging Bateleur from the protected Park enter these areas, as well as nesting site disturbance, could have been part of the reason for this decline. Poisoned and suspected poisoned Bateleurs have been found in the Park during the study period. There was no obvious decline in active Tawny Eagle nesting territories.     

THE INFLUENCE OF THE ENVIRONMENT ON BREEDING SUCCESS OF A SUBURBAN POPULATION OF CRESTED BARBETS TRACHYPHONUS VAILLANTII

Van Zyl, A.J. 1994. The influence of the environment on the breeding success of a suburban population of Crested Barbets Trachyphonus vaillantii. Ostrich 65: 291–296.

I studied the breeding biology of the Crested Barbet Trachyphonus vaillantii in Colbyn, a suburb east of Pretoria, South Africa, for nine breeding seasons from 1981 to 1989 to examine patterns in annual breeding success, breeding attempt success in multiple broods, and rainfall. The modal incubation period was 14 days and the nestling period ranged from 28 to 31 days. Average clutch size for all the years was 3,3 eggs/clutch and there was no significant difference in clutch size or number of young fledged/nest between years. On average, Crested Barbet pairs made 2,4 breeding attempts/season. There was no difference in clutch size or breeding success between the breeding attempts. Crested Barbets nesting in natural nests laid on average larger clutches than those in artificial nestboxes, but had non-signficantly lower breeding success. Failure to raise Crested Barbet chicks was attributed to parasitism by Lesser Honeyguides Indicator minor, bee swarms occupying nestboxes, and flooding of natural nests. Breeding performance was not correlated with rainfall or adult body size. The suburban environment may be less variable than a natural environment, resulting in a stable breeding Crested Barbet population.     

NOTES ON THE BREEDING OF THE BOKMAKIRI

Counting Saddle-billed Storks in a study area the size of the Kruger National Park, at 2.2 million ha, is difficult because the birds are long-lived, sparse in the landscape and have large home ranges. Aerial surveys conducted to date provide an estimate with no measure of data dispersion, thence precision. The aim of this study was to estimate the population size within associated confidence limits using a modified mark–recapture field method. The vehicle survey, conducted shortly after rainfall in the area, did not produce results with known precision under these conditions. A repeat of this census in spring, after the peak breeding season and when surface water is confined to the larger rivers and dams, should yield different results. A photographic census technique yielded sufficient information to construct a population registration database. Individual identification profiles indicate that there are at least 40 adult Saddle-billed Storks in the southern part of the Kruger National Park. This is considered the minimum number of known-to-be-alive individuals in this area. In this paper, the Cormack–Jolly–Seber mark– recapture model was used to return an estimate of the population size for each capture occasion.