ON THE BIRDS OF THE SANDVELD KALAHARI OF SOUTH WEST AFRICA

Keffen, R. H. &; Jarvis, M. J. F. 1984. Some measurements relating to Ostrich eggs. Ostrich 55:182-187.

Eggs from wild Zimbabwean Ostriches Struthio camelus australis and domesticated South African hybrid birds, were compared. Formulae were tested to determine their accuracy when used to calculate egg weights, surface area and density. Calculated values were compared with some actual measurements. The main motivation for the study was the need to calculate fresh egg weights of wild Ostriches, as an aid to determining weight loss during incubation under natural conditions. Eggs from wild birds were, on average, smaller than those from domesticated birds, even though the wild adults were larger than domesticated birds. However, newly batched chicks from hybrid eggs weighed less than those from wild eggs.     

鸵鸟性别鉴定的分子标记方法

鸵鸟(Struthiocamelus)属于平胸总目鸟类,雌雄鸵鸟在性成熟前外部形态相同,很难通过外观和形态来鉴定性别,给早期分群饲养造成了很大的困难。实验利用鸵鸟羽毛提取基因组DNA,之后利用EE0.6和CHD基因中2个引物组合对3对已知性别和9只未知性别鸵鸟的性别基因片段进行特异性扩增。结果显示,这对引物组合在雄性鸵鸟的DNA中未扩增出片段,在雌性鸵鸟DNA中扩增出1条片段,可以对鸵鸟的性别作出准确鉴定,从而解决幼雏期鸵鸟难以从外貌上区分其性别的问题。     

The white colour of the Ostrich ( Struthio camelus ) egg is a trade-off between predation and overheating

Most ground nesters lay pigmented eggs, and egg pigmentation generally matches the environment. Pigmentation of eggs has evolved as a protective device against predation, but dark-pigmented eggs can be susceptible to overheating when exposed to solar radiation. The Ostrich (Struthio camelus) lays white eggs that are unattended for the first few weeks before incubation, and are quite visible to predators. To evaluate the effect of colour on the surface and core temperatures, we painted some Ostrich eggs dark brown or white, and left some unpainted (control), and exposed all of them directly to the sun during the day. The surface and core temperatures of brown eggs were significantly higher than those of the white-painted and control eggs. In addition, the core temperature of brown eggs exceeded 37.5°C, which is the temperature at which embryo mortality starts to increase. In a second experiment, we placed eggs (brown-painted and control) in various types of vegetation to study their visibility to an observer walking towards them. The white eggs were discovered from a significantly longer distance than the brown eggs, indicating that the predation risk may be much higher for white eggs. The results thus suggest that white eggs minimise overheating and allow the Ostrich to leave its eggs unattended before incubation starts, but they are more susceptible to predation.     

Book Reviews

Adams, N.J., Kerley, G.I.H. & Watson, J.J. 1999. Disturbance of incubating African Black Oystercatchers: is heating of exposed eggs a problem? Ostrich 70(3&4): 225–228.

We measured temperatures of incubated and exposed eggs of African Black Oystercatchers Haematopus moquini nesting in coastal dunes, Algoa Bay, South Africa through three of the 10 hottest days of summer during the 1994/95 breeding season. Mean incubation temperature was 34.4 ± 0.7°C (range: 32.2–37.0; n=3). The average maximum temperature attained by exposed dummy eggs, averaged higher at 37.4 ± 2.7°C (n=5). The absolute maximum recorded for exposed eggs was 40.1°C. These temperatures are within lethal limits measured for other birds and suggests that heating of exposed eggs after disturbance of incubating was not a direct factor in explaining variation in breeding success of oystercatchers in the Alexandria Dunefield, Algoa Bay.     

THE POPULATION,ECOLOGY AND CONSERVATION OF THE BLACK OYSTERCATCHER HAEMATOPUS MOQUINI

Summers, R. W. & Cooper, J. 1977. The population, ecology and conservation of the Black Oystercatcher Haematopus moquini. Ostrich 48:28-40.

The population of Black Oystercatchers Haematopus moquini in the southwestern Cape, South Africa, was estimated to be 2 942 birds. Birds occurred most abundantly on coastal islands and were also abundant on mixed (sandy and rocky) shores of the mainland. Sandy shores and coastal wetlands supported few birds. Black Oystercatchers bred mainly from December to February with the number of clutches present reaching a peak in the first half of January. The most frequent clutch size was two eggs, the mean clutch size was 1,81. No significant differences were found in either linear dimensions or mass between the first and second eggs. The mean proportion of juveniles in groups of birds in July was 3,6 % suggesting a low recruitment to the adult population. The breeding population at Marcus Island is apparently sedentary throughout the year. The primary moult season for adults extends from March to October (eight months). Introduced mammalian predators should be controlled on islands and important mainland breeding sites should be protected by the creation of nature reserves and restricting human access during the breeding season.     

Pesticide levels in stork and spoonbill eggs from the Okavango Delta,Botswana

Motalaotte, S. & Bouwman, H. 2000. Pesticide levels in stork and spoonbill eggs from the Okavango Delta, Botswana. Ostrich 71 (1&2):344.

Ecotourism in the Okavango Delta is one of the major sources of foreign revenue for the Republic of Botswana. Promoting this region is therefore vital to sustainable development. One of the concerns was the past use of organochlorine pesticides to combat tsetse fly. This study looked at the levels and possible risk this use poses to Marabou storks and African Spoonbills, as well as some other birds, from this region. One particular breeding colony also experienced a decline in breeding success, the cause of which is unknown. DDE was present in almost all the eggs and blood sampled, while DDD, DDT and Dieldrin were also found in many. These pesticides are therefore present in the food chain and should be closely monitored to determine any temporal trends.     

SOME PHYSICAL REQUIREMENTS FOR OSTRICH EGG INCUBATION

Jarvis, M. J. F., Keffen, R. H. & Jarvis, C. 1985. Some physical requirementsfor Ostrich egg incubation. Ostrich 56: 42–51.

Eggs from wild and domesticated Ostriches Struthio camelus australis were studied to determine temperature and humidity requirements for successful incubation. Wild eggs in Zimbabwe included some collected and incubated artificially, and others that were naturally incubated until just before hatching. Egg-weight losses during incubation were measured. The eggs artificially incubated at 35 °C to 36°C and 40–42% relative humidity, lost nearly the same weight as did eggs in naturally incubated nests. Comparisons were made between the wild eggs and chicks, and those from domesticated hybrid-strain Ostriches in Bophuthatswana. The discussion outlines some of the remaining problems associated with Ostrich egg incubation.     

The influence of mist and rain on the reproductive success of the Blue Swallow Hirundo atrocaerulea (1995–96)

Evans, S.W. & Bouwman, H. 2000. The influence of mist and rain on the reproductive success of the Blue Swallow Hirundo atrocaerulea. Ostrich 71 (1 & 2): 83–86.

Due to the locality of the Blue Swallow Natural Heritage Site it appears that the birds have no alternative but to forage in the mist. The birds cease foraging as soon as it starts raining. Eight eggs failed to hatch after a week in which rainfall occurred for 60% and mist for 85% of the time. Later in the season a further six eggs failed to hatch after a week in which rainfall occurred for 18% and mist occurred for 65% of the time. The only mortality of two nestling Blue Swallows occurred at the end of a week in which rainfall occurred for 65% and mist was recorded for 85% of the time. At a nest containing three eggs, during the presence of mist (16°C wet/19°C dry) the female Blue Swallow spent a mean of 52 min h^?1 foraging and therefore only a mean of 8 min h^?1 incubating. In the absence of mist (21°C wet/26°C dry) the female Blue Swallow spent a mean of 25 min h^?1 foraging and therefore 35 min h^?1 incubating. Rainfall did not occur during the monitoring of this nest. It appears that the mist greatly reduces the foraging efficiency of the birds and that rainfall duration impacts on the birds by limiting the available foraging time.     

The breeding biology of the House Sparrow Passer domesticus at Blantyre,Malawi

Nhlane, M.E.D. 2000. The breeding biology of the House Sparrow Passer domesticus at Blantyre, Malawi. Ostrich 71 (1 & 2): 80–82.

The breeding biology of the House Sparrow Passer domesticus was studied from 1989–1990. The birds bred throughout the year at this site. Modal clutch size varied from three to four eggs, with a mean clutch of 3.9. The average incubation period was 11.5 days, and the fledgling period 15.4 days. The clutch size of the House Sparrow varied seasonally and was larger from November to June, and smaller from July to October. Chick mortality at Chikunda was attributed to starvation, abandonment, predation, low birth weight, accidental deaths and parasitism.     

4. CLIMPSES OF THE NARINA TROGON

Bertram, B. C. R. &; Burger, A. E. 1981. Aspects of incubation in Ostriches. Ostrich 52:36-43.

We studied incubation in domesticated Ostriches Struthio camelus in South Africa and wild Ostriches in Kenya. Although the eggs were large, with relatively high thermal capacities, unattended eggs exposed to the sun reached dangerously high temperatures (40,5°C). Experimental exposure of fresh eggs to the sun for seven days prior to incubation greatly reduced the percentage of embryos which developed, and no embryos survived 15 days of exposure. In the wild. Ostriches frequently shade their eggs in the pre-incubation period to prevent overheating.

During natural incubation, temperatures in the eggs (range 30,8-33,8°C) and of nest-air (31,9-34,6°C) were remarkably constant, despite the daily ambient fluctuations of air temperatures (17,8-38,9°C). Similarly the humidity of the nest-air (39–52%) was lower and less variable than the ambient air (39–72%). Water loss during 42 days of incubation was 11–12% of initial egg weight and, in addition, early laid eggs lost 3–4% during the 2½-3 week pre-incubation period. The water vapour conductivity and the daily water loss of Ostrich eggs were similar to those of other birds, in proportion to epg size, despite the arid environment inhabited by Ostriches. Some of the constraints on the feeding and breeding behaviour of Ostriches imposed by the physical requirements of their eggs are discussed.     

5. A NOTE ON THE PARADISE WHYDAHS

Vernon, C. J. 1975. Seventeenth ringing report for southern African. Ostrich 46:125-128.

A report on ringing activities in southern Africa from July 1973 to June 1974 is presented. A total of 51 561 birds of 451 species were ringed and are analysed according to distribution of ringers, groups of species and recovery rates. A list of those birds living longer than ten years is given. Analyses are needed of the most frequently ringed species in order to give greater purpose to future ringing.     

Levels of organochlorine pesticides in raptors from the North-West Province,South Africa

Smith, I. & Bouwman, H. 2000. Levels of organochlorine pesticides in raptors from the North-West Province, South Africa. Ostrich 71 (1 & 2): 36–39.

The levels of organochlorine pesticides in raptors from southern Africa remain poorly known. We found generally low levels of DDE, dieldrin and endosulfan in the blood of 20 raptors from the North-West Province, South Africa. Despite the low levels, these pesticides were present in all the birds, raising the issue of combined effects. The continuing use of organochlorines, despite their ban in many developed countries, remains. Trends in contamination and use elsewhere should therefore be monitored on a more regular basis, while the sampling of blood, rather than eggs seems to provide adequate information. The effects of other pesticides should also be investigated.     

OBSERVATIONS ON THE BREEDING OF THE PIED CROW AND GREAT SPOTTED CUCKOO IN NORTHERN NIGERIA

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.

The breeding cycle of the Pied Crow Corvus albus was studied in 1971. The birds bred in the wet season and all of 23 pairs were single-brooded. They appeared to nest territorially, and mostly close to human habitations. Average clutch size was 4.8 eggs and the greenish eggs were either pale and lightly marked, or darker and heavily marked. The average incubation and fledging periods were 181/2 and 38 days respectively. Chicks hatched asynchronously. Five crow nests were found parasitised by the Great Spotted Cuckoo Clamator glandarius and it appeared that only one hen cuckoo was responsible. The cuckoo apparently did not remove, or even crack, host eggs. One instance of an adult cuckoo feeding a juvenile was seen. In terms of growth increments a cuckoo chick substituted for one-half a crow chick but developed faster and fledged in nearly one-half the time. The cuckoo reduced host breeding success practically to zero apparently by indirect means, which contrasts with its situation in Europe.     

Migratory Birds in Malawi

Banda, H.M. 2000. Migratory Birds in Malawi. Ostrich 71 (1 & 2): 183.

Some literature review and brief field observations on migratory birds were carried out from November 1987 to October 1992. Migratory birds and their natural habitats in Malawi are under threat. These threats include deforestation, uncontrolled bush fire, poorly planned development, poor habitat management, lack of knowledge and understanding of the importance of migratory birds and the natural habitats by the public.

This paper discusses the threats and their possible solutions, which would improve management of the remaining migratory bird habitats and public awareness of the importance of migratory birds and their habitats.     

The Kilum-Ijim Forests IBA in Cameroon: monitoring biodiversity using birds as indicators

McKay, C. & Coulthard, N. 2000. The Kilum-Ijim Forests IBA in Cameroon: monitoring biodiversity using birds as indicators. Ostrich 71 (1 & 2): 177–180.     

REMARKS ON THE DISTRIBUTION OF BIRDS COLLECTED IN MASHONALAND AND EASTERN SOUTHERN RHODESIA (Part I)

Oatley, T. B. 1983. Twenty-third ringing report for southern Africa. Ostrich. 54:141-149.

Bird ringing activities in southern Africa are summarized for a two-year period from July 1979 to June 1981. A total of 42 374 birds were ringed. Much ringing effort was devoted to marine buds. Palaearctic migrants comprised nearly 12% of the birds ringed, with waders, swallows and warblers being the most frequently ringed families. There were 747 recoveries or recaptures reported during the reviey period, of which 73 were foreign-ringed birds. The remainder involved 103 species of birds, only nine of which contributed 10 or more recoveries to the total. Five of the nine are marine birds and collectively account for 55% of all recoveries and recaptures. A selected list of recoveries and recaptures of southern African-ringed birds is given.     

PLUMAGE CHANGES IN THE MALE MACCOA DUCK

Clark, A. 1974. Plumage changes in the male Maccoa Duck. Ostrich 45: 251–254.

Maccoa Duck Oxyura mi ccoo counts made at various waters in the Transvaal and Orange Free State, South Africa, in which the numbers are separated according to plumage, are presented and discussed in the light of the work done by Siegfried (1968, 1970) on this species. Males invariably outnumber females and the indications are that Transvaal birds move out of the area during winter when most males are in non-breeding plumage. There is little difference in the pattern of plumage changes between Transvaal and Cape birds.     

MINUTES OF THE ANNUAL GENERAL MEETING OF THE SOUTH AFRICA ORNITHOLOGICAL SOCIETY,HELD IN DURBAN ON 11th May 1968

Raseroka, B. H. 1975. Breeding of the Hadedah Ibis. Ostrich 46:208-212.

The Hadedah Ibis Lostrychia hagedash is a common species in the Eastern Cape Province. Nest construction and nesting are described. Normally three eggs are laid, but survival of the nestlings until they can leave the nest is low.     

Habitat of the Golden Nightjar Caprimulgus eximius

The Ostrich communal breeding system involves several females laying in a single nest. Only the ‘major’ female and the territorial male, however, provide parental care from incubation to fledging of chicks. Eggs are turned and displaced frequently upon the onset of incubation, and the major female evicts excess eggs out of the nest when the number of eggs is above a specific threshold level. A previous study indicated that the major female ostrich recognises her own eggs and selectively evicts eggs of minor females based on size, shape and shell texture. Our aim was to investigate if accepted and ejected eggs differ in colour characteristics. We quantified colour by measuring egg reflectance spectra, which were subsequently analysed using a visual model approach. Within clutches, there were no significant differences in colour between accepted and ejected eggs. These results suggest that female ostriches do not discriminate against foreign eggs based on deviations in colour.