Showing papers in "Ostrich in 1991"
TL;DR: Velasquez et al. as mentioned in this paper studied the seasonal abundance, habitat selection and energy consumption of waterbirds at the Berg River estuary, South Africa, and found that intertidal mudflats are the favoured feeding habitat of the majority of species on the estuary during the low tide period.
Abstract: Velasquez, C.R., Kalejta, B. & Hockey, P.A.R. 1991. Seasonal abundance, habitat selection and energy consumption of waterbirds at the Berg River estuary, South Africa. Ostrich 62:109-123. The distribution and abundance of waterbirds at the Berg River estuary were studied between September 1987 and April 1989. The estuary supports an unusually high density of waterbirds, especially of Pale-arctic migrant waders, and is a site of subregional importance for at least nine species. Intertidal mudflats are the favoured feeding habitat of the majority of species on the estuary during the low tide period. Low tide feeding densities on saltmarshes are mud less than on mudflats, but saltmarshes are important as roost sites, high tide feeding sites, and in counteracting the negative hydrological consequences of development. The current conservation status of the estuary is not commensurate with its importance as a waterbird habitat and, given the current threats facing the estuary, enhanced protection at the nationa...
33 citations
TL;DR: Bashoff et al. as mentioned in this paper studied the toporaphical and biogeoraphic variation in the prey of the Black Eagle in the Cape Province, South Africa.
Abstract: Summary 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: s...
31 citations
TL;DR: Underhill et al. as discussed by the authors described the role of large-scale data collection projects in the study of southern African birds, including checklists, migration enquiry, atlas projects, censuses, bird ringing and recoveries, biometric data, nest record cards, moult cards and beached birds.
Abstract: Summary Underhill, L.G., Oatley, T.B. & Harrison, J.A. 1991. The role of large-scale data collection projects in the study of southern African birds. Ostrich 62:124-148. The major ornithological data collections in southern Africa (checklists, migration enquiry, atlas projects, censuses, bird ringing and recoveries, biometric data, nest record cards, moult cards and beached birds) are described. For each project, current volumes of data are tabulated. The Southern African Bird Atlas Project database contained 5,0 million records in December 1990. 1,25 million birds of 810 species had been ringed with South African Bird Ringing Unit rings by June 1989, resulting in 22 000 recoveries. There were more than 100 recoveries for 27 species. The nest record card scheme of the Southern African Ornithological Society had 117 000 cards on file in February 1990, representing 696 species, with more than 1 000 cards for 18 species. There were 4 040 cards of 380 species in the moult record scheme. African Seabird Group ...
30 citations
TL;DR: The main non-avian prey were fish and goose barnacles Lepas sp.
Abstract: Summary Ryan, P.G., & Moloney, C.L. 1991. Prey selection and temporal variation in the diet of Subantarctic Skuas at Inaccessible Island, Tristan da Cunha. Ostrich 62:52-58. More than 2 500 prey items of Subantarctic Skuas Cuthuructa anturcricu were identified from regurgitated pellets collected at a roost of non-breeding skuas during summer 1989–90 at West Point, Inaccessible'Is-land. Most prey items (96,5%) were birds, primarily burrow-nesting procellariiforms. Sixteen bird species were recorfed in the diet, but five secies accounted for 94,6% of identifiable prey remains: Whitebellied Storm Petrel Fieettu grullariu (53,5%), Whitefaced Storm Petrel Pelugodrorna marina 15,1%), Broad-billed Prion Pacaptilu vittutu (14,0%), Great Shearwater Puffinus gruvis (7,3%), and Iommon Diving Petrel Pelecunoids urinutrix (4,7%). Petrel chicks were important in the diet, particularly Great Shearwaters. The main non-avian prey were fish and goose barnacles Lepas sp., but their importance may have been underestimated. T...
26 citations
TL;DR: Bashoff et al. as mentioned in this paper investigated spatial and temporal abundance patterns of water-birds in the southern Cape Province, and the fluctuating status of submerged aquatic macrophytes and the trophic status of the waterbodies.
Abstract: Summary Boshoff, A.F., Palmer, N.G. & Piper, S.E. 1991. Spatial and temporal abundance patterns of water-birds in the southern Cape Province. Part 2: Waterfowl. Ostrich 62:178-196. Waterfowl (ducks, geese, moorhens, gallinules, coot) were counted, and water-level and water transparency measured, on a monthly basis from 1980 to 1983 or 1984, at the six waterbodies comprising the Wilderness-Sedgefield Lakes Complex, southern Cape Province. The fluctuating status of the submerged aquatic macrophytes, and the trophic status of the waterbodies, was documented. The counts reflect the monthly status o the birds, and allow the calculation of densities (birds/ha). Linear and logarithmic models aided the interpretation of the count data. Spatial and temporal patterns and trends are described, and discussed in relation to changes in water-level, water transparency and aquatic macrophyte biomass regimes in the study area. Cyclical fluctuation in Potamogeton pectinatus biomass, and Its effect on Red-knobbed Coot numbe...
18 citations
TL;DR: Bashoff et al. as discussed by the authors studied the spatial and temporal abundance patterns of water-birds in the southern Cape Province, and the fluctuating status of the submerged aquatic macrophytes and the trophic status of waterbodies.
Abstract: Summary Boshoff, A.F., Palmer, N.G. & Piper, S.E. 1991. Spatial and temporal abundance patterns of water-birds in the southern Cape Province. Part 3: Wading birds. Ostrich 62:197-214. Wading birds (herons, egrets, spoonbills, flamingoes and waders) were counted, and water-level and water transparency measured, on a monthly basis from 1980 to 1983 or 1984, at the six waterbodies comprising the Wilderness-Sedgefield Lakes Complex, southern Cape Province. The fluctuating status of the submerged aquatic macrophytes, and the trophic status of the waterbodies, was documented. The counts reflect the monthly status of the birds, and allow the calculation of densities (birds/ha). Linear and logarithmic models aided the interpretation of the count data. Spatial and temporal patterns and trends are described, and discussed in relation to changes in water-level, water transparency and aquatic macrophyte biomass regimes in the study area. Water-level was an important environmental parameter and was generally negativel...
17 citations
TL;DR: Bashoff et al. as mentioned in this paper investigated the spatial and temporal abundance patterns of water-birds in the southern Cape Province and found that some species exhibited significant correlations with water-level and/or water transparency, and some exhibited abundance peaks at the waterbodies in a regular month.
Abstract: Summary Boshoff, A.F., Palmer, N.G. & Piper, S.E. 1991. Spatial and temporal abundance patterns of water-birds in the southern Cape Province. Part 1: Diving and surface predators. Ostrich 62:156-177. Diving and surface feeding waterbirds (grebes, cormorants, gulls, terns, kingfishers) were counted, and water-level and water transparency measured, on a monthly basis from 1980 to 1983 or 1984, at the six waterbodies comprising the Wilderness-Sedgefield Lakes Complex, southern Cape Province. The fluctuating status of the submerged aquatic macrophytes, and the trophic status of the waterbodies was documented. The counts were considered to be reasonably accurate, allowing the calculation of densities (birds/ha). Spatial and temporal patterns and trends are described and discussed; linear and logarithmic models aided the interpretation of the data. Some species exhibited significant correlations with water-level and/or water transparency, and some exhibited abundance peaks at the waterbodies in a regular monthl...
17 citations
TL;DR: The seasonal movements of Gurney's Sugarbird Promerops gurneyi were studied in the Lydenburg area, eastern Transvaal, South Africa when the birds left the mountains at the end of the flowering period of Protea roupelliae.
Abstract: Summary De Swardt, D. H. 1991. The seasonal movements of Gurney's Sugarbird Promerops gurneyi in the Ly-denburg area, Transvaal. Ostrich 62: 40–44. The seasonal movements of Gurney's Sugarbird Promerops gurneyi were studied in the Lydenburg area, eastern Transvaal, South Africa. Influx into the suburban habitat occurred durin the winter when the birds left the mountains at the end of the flowering period of Protea roupelliae. Birifs were mistnetted and each adult colour-ringed with a unique combination for individual recognition. In all, 256 Sugarbirds were ed in the mountain habitat and 50 in the suburban habitat. Of the unringed individuals 22,2 % were ted on cliffs with aloes and 79,3 % around P. roupelliae clumps late in the season. Of the ringed birds 25 (9,7%) were retrapped at sites in the mountain and 10 (3.9%) showed seasonal movements; 6 (8,3%) were recaptured in the same town localities where originally ringed. Mean distance moved was 7 km. An overall recapture rate of 7,5% was recorded during ...
16 citations
TL;DR: Laying dates for a population of individually marked Greater Kestrels Falco rupicoloides near Pretoria, South Africa, were determined for 89 nesting attempts during 1975–1988.
Abstract: Summary Kemp, A C 1991 Timing of laying by Greater Kestrels Fulco rupicoloides near Pretoria, South Africa Ostrich 62: 35–39 Laying dates for a population of individually marked Greater Kestrels Falco rupicoloides, on grass- and croplands near Pretoria, South Africa, were determined for 89 nesting attempts during 1975–1988 Laying occurred in the austral spring between 23 July and 11 November Timing of laying was negatively correlated with rainfall of the previous summer and positively correlated with rainfall of the winter and spring preceding laying Success in fledging young was significantly higher for clutches laid before the median laying date of 1 September and for clutches laid after seasons of above average rainfall
14 citations
TL;DR: Adult and juvenile starlings undertook a comlete post-breeding moult of European Starlings Srurnus vulgaris at Dassen Island, South Africa, and on average, juveniles commenced moult 19 d later than did adults.
Abstract: Summary Cooper, J. & Underhill, L.G 1991. Breeding, mass and primary moult of European Starlings Sturnus vulgaris at Dassen Island, South Africa. Ostrich 62: 1–7. European Starlings Srurnus vulgaris breed from September to November at Dassen Island, South Africa. Mean clutch size was 3,8 and mean brood size 2,8. An estimated 0,7 juvenileslbreeding attempt survived to 2–3 months of age. Winter (post moult) masses were higher than in summer in juveniles, but not in adults. Adult and juvenile starlings undertook a comlete post-breeding moult. Based on percentage feather mass grown, primary moult took 108 d in aduis and 106 d in juveniles. On average, juveniles commenced moult 19 d later than did adults.
14 citations
TL;DR: Aerial displays of sky-dancing displays of Circus harriers and African Marsh Hamers Circus ranivorus perform aerial dances to help untangle the marsh harrier complex.
Abstract: Simmons, R. 1991. Comarisons and functions of sky-dancing displays of Circus harriers: untangling the marsh harrier complex. Ostrich 62:45-51. African Marsh Hamers Circus ranivorus perform aerial d...
TL;DR: The small effect of breeding status on prey species composition shows that temporal and geographical variation in prey availability is more important than breeding status in affecting diet cornposition of the Cape Gannet.
Abstract: Summary Berruti, A. 1991. Comparison of the diet of breeding and nonbreeding Cape Gannets Morus capensis. Ostrich 62:8-12. The effects of breeding status on the diet composition of Cape Gannets Morus capensis were tested at two colonies in the western Cape, South Africa. At both colonies, there were no significant differences in the species composition of the diet, but the mean energy content of regurgitations of breeders was significantly greater. Although the regurgitations of breeders were heavier and contained more fish at both colonies, only the number of fish per regurgitation from breeders at one colony was significantly greater. Birds feeding chicks at Malgas Island took significantly shorter fish than nonbreeders. The small effect of breeding status on prey species composition shows that temporal and geographical variation in prey availability is more important than breeding status in affecting diet cornposition of the Cape Gannet.
TL;DR: Pepler et al. as discussed by the authors used a survey of nest sites and nest site characteristics to obtain an estimate of the breeding density of the Peregrine Falcon Falco peregrinus minor in the southwestern Cape, South Africa.
Abstract: Summary Pepler, D., Van Hensbergen, H.J. & Martin, R. 1991. Breeding density and nest site characteristics of the Peregrine Falcon Falco peregrinus minor in the southwestern Cape, South Africa. Ostrich: 62: 23–28. A survey of nest sites and nest site characteristics is used to obtain an estimate of the breeding density of the Peregrine Falcon Falco peregrinus minor in the southwestern Cape, South Africa. The breeding density from a small intensively studied area around the town of Stellenbosch is extrapolated to the region. This extrapolation is justified since nest site characteristics suggest that suitable sites are widespread in the region. Lower and upper estimates of 48 and 95 pairs respectively were obtained for the area above 300 m. This gives densities of one pair per 199 km2 for the lower estimate and one pair per 100 km2 for the upper estimate. For the entire study area the densities are one pair per 806 km2 and 407 km2 respectively.
TL;DR: It is concluded that the most frequently observed clutch and brood sizes (two or three) are the most productive, and that there is no apparent advantage of brood parasitism for the parasite.
Abstract: Summary Earle, R.A. & Underhill, L.G. 1991. The effects of brood size on growth of South African Cliff Swallow Hirundospilodera chicks. Ostrich 62: 13–22. We aimed to determine if growth rates of South African Cliff Swallow Hirundo spilodera chicks varied between broods of different sizes, with a view to understanding conspecific brood arasitism. Reression analyses and logistic growth curves were used to model body-mass and wing-length of chicks at Afferent ages to interpret observed differences in the growth of chicks in experimentally established brood sizes. Only the regression analyses showed meaningful differences between brood sizes. The swallows were unable to raise broods of four or five chicks successfully, and we conclude that the most frequently observed clutch and brood sizes (two or three) are the most productive, and that there is no apparent advantage of brood parasitism for the parasite.
TL;DR: The fossil bird remains as well as those of other vertebrates indicate that the Pleistocene “Grey Lake 2” was surrounded by a mosaic of different aquatic and terrestrial biotopes.
Abstract: Summary Bochenski, Z. 1991. Pleistocene bird fauna from Bir Tarfawi (Egyptian Western Desert). Ostrich 62: 29–34. At Bir Tarfawi, an archaeological site in the Egyptian Sahara dated to about 135000 years (before present), 202 bone fragments were identified as belonging to 24 bird species or genera. Most of the material is apparently from owl pellets. The birds represent aquatic and terrestrial forms and include different zoogeoraphical elements; Afrotropical species such as Phalacrocorax africanus, Gyps africanus, cf. Neotis denfami, Fulica cristata, Oena capensis and Corvus albus, as well as Indo-African species such as cf. Bubulcus ibis and Turnix cf. sylvatica. The fossil bird remains as well as those of other vertebrates indicate that the Pleistocene “Grey Lake 2” was surrounded by a mosaic of different aquatic and terrestrial biotopes.
TL;DR: There was no significant difference between growth-rates of body mass and of wing length for hand-reared and wild nestlings, and body mass at any given age proximally determined by fluctuations in body water and fat reserves, and ultimately determined by variations in food provisioning.
Abstract: Summary Komen, J. 1991. Growth in Cape Vulture nestlings. Ostrich 62: 149–155. Wild and hand-reared Cape Vulture Gyps coprotheres nestlings were monitored during two breeding seasons in 1981 and 1982. Growth and behavioural development were examined, and changes in body mass were related to changes in body water and fat reserves. There was no significant difference between growth-rates of body mass and of wing length for hand-reared and wild nestlings. Body water was correlated with body mass (r2 = 0,995), and fat-free body mass was correlated with body water (r2 = 0,999) during growth, thus providing estimates of fat reserves in wild nestlings Growth followed. a sigmoid pattern determined by the consistent deposition of body constituents, with body mass at any given age proximally determined by fluctuations in body water and fat reserves, and ultimately determined by variations in food provisioning.
TL;DR: Craig, A.K., Hulley, P.E. and W.H. as discussed by the authors investigated the behavior of pairs of Palewinged Starlings and compared it with other Onychognathus species.
Abstract: Craig, A.J.F.K., Hulley, P.E. & Walter, G.H. 1991. The behaviour of Palewinged Starlings, and a comparison with other Onychognathus species. Ostrich 62:97-108. Pairs of Palewinged Starlings associa...