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Abstract
Clark, A. 1974. The status of the whistling ducks in South Africa. Ostrich 45:1-4. Since the 1920's the status of Dendrocygna viduata and D. bicolor has changed from that of an irregular to that of a regular species in the Transvaal, Zululand, Natal and Orange Free State. In more recent years their numbers have shown a steady increase and breeding has been established. D. viduata numbers built up more quickly than D. bicolor and it has become an established resident whereas D. bicolor is primarily a summer visitor.In the Western Cape Province there has been little change in the status of either species but there are indications that D. viduata is appearing mote regularly in the Eastern Cape Province. The position in East Griqualand and the Transkei is obscure. In South West Africa, excluding the north east corner, D. viduata remains irregular and D. bicolor rare.The preference shown by both species for areas where sewage effluent is disposed of and for new storage dams inevitably links their spread and increase with that of the human population.
This is the complete set of references for both Volumes 1 and Volume 2 of The Atlas of Southern African Birds
In the semi-arid regions of South Africa, stock-watering ponds and dams have become an important aquatic habitat for several species of waterfowl. We monitored the diurnal activities of breeding white-faced whistling ducks Dendrocygna viduata on stock-watering ponds and dams associated with the Nyl River floodplain, South Africa, from December 1992 to March 1993. Activity patterns diverge from those of north-temperate breeding ducks; apparently a result of differences in environment and resource availability. While most species of north-temperate breeding ducks spend large portions of the day aquatic foraging, male and female white-faced whistling ducks foraged on stock-ponds for only 4.0% and 9.8% of the day, respectively, white-faced whistling ducks were able to satisfy most of their daily dietary requirements during crepuscular foraging flights to neighboring Panicum schinzii fields. This permitted them to spend most of the day in comfort-related activities (sleeping, loafing, preening) (males 49% of the day, females 67%), which presumably has important energetic implications for reproducing birds. Low foraging effort is also indicative of a low aquatic resource availability on the stock-watering ponds studied, relative to north-temperate wetlands. Thermal stress associated with high summer temperatures in South Africa apparently influenced daily activity patterns because feeding, locomotion, courtship, and aggression were rarely observed during the hottest parts of the day. While stock ponds provide limited foraging opportunities, they do supply habitat for comfort-related activities, a critical requirement of waterfowl.
Foods of white-faced whistling ducks Dendrocygna viduata were studied relative to sex, age, time of winter and spring, habitat type, and molt intensity in northern KwaZulu-Natal, South Africa, 1995. Adults and juveniles were collected on a naturally occurring pan (Yengweni Pan) and a large water storage dam (Pongolapoort Dam) during early winter (June), late winter (August) and spring (October). While the proportions of individual foods varied throughout the winter and spring and between the two collection sites, there were no sex or age-related dietary differences at either of the sites (P > 0.05). The seeds of moist soil (>99% aggregate dry mass) and aquatic plants (>97%) were the principal dietary items of birds using the Pongolapoort Dam and Yengweni Pan, respectively. While extensive submerged plant communities permit birds to consume large quantities of aquatic seeds on the Yengweni Pan, large fluctuations in water level on the Pongolapoort Dam impede aquatic plant establishment, forcing birds to forage elsewhere. The most commonly consumed seeds contained fat and crude protein levels ranging between 0.82-1.60 and 7.00-12.69%, respectively. Invertebrates were minor dietary items (<1.0%) and although birds tended to consume higher levels of animal matter during the wing-molting period, invertebrate consumption was not correlated with molt intensity. Continued drainage and overgrazing of shallow pans and damming of floodplain systems will adversely affect the aquatic foods used by wintering white-faced whistling ducks, particularly during wing-feather molt. The consequences of large-scale water abstraction schemes and wetland drainage may be even more severe for diving ducks, as they are incapable of foraging in terrestrial habitats.
CLARK, A. 1976. Observations on the breeding of whistling ducks in Southern Africa. Ostrich 41 59–64.Records collected since 1954 show that Dendrocygna viduutu breeds in the Transvaal, Natal and Rhodesia, choosing for the most part a limited mid-summer period when most rains can be expected. D. bicolor records for the Transvaal and Natal show a similar pattern but in Rhodesia breeding is not so restricted. In the Transvaal and Natal most records were obtained near the more populated areas at man-made or artificial breeding grounds. Information is given on nest sites and construction, clutch and brood size, and the behaviour of nesting birds. The percentages of juveniles in flocks of D. viduuta following the breeding season are compared showing the apparent effect of rainfall on breeding success.
Clark, A. 1978. Some aspects of the behaviour of whistling ducks in South Africa. Ostrich 49:31-39.The behaviour of the Whitefaced Whistling Duck Dendrocygna viduata and the Fulvous Whistling Duck D. bicolor wasstudied between 1971 and 1974 on the Witwatersrand, Transvaal. The paper describes and compares behaviour associated with feeding, voice, flight, agonistic situations and copulation in the two species.
Geldenhuys. J. N. 1976. Relative abundance of waterfowl in the Orange Free State. Ostrich 47: 27–54.During 1971–1972 a census was conducted in the Orange Free State, Republic of South Africa, to investigate the relative abundance of duck species. The survey was carried out in both the wet and dry seasons. The results are presented by plotting seasonal distribution within quarter degree squares and classifying all records for each species into group size classes. Comparisons are made of total numbers, frequencies of occurrence and seasonal habitat utilization. Overall abundance, arranged according to percentages of the total duck population, was as follows: Rare to uncommon (< 1%)—White-faced Duck, Whistling Duck. Hottentot Teal, Maccoa Duck, Black Duck, White-backed Duck and Knob-billed Duck; common (4–9%)-Cape Teal, Cape Shoveller, Southern Pochard. Red-billed Teal and Spurwinged Goose; very common (19–20%)—Yellow-billed Duck and South African Shelduck; abundant (32%)—Egyptian Goose.
Many water bodies in arid southern Africa are seasonal and waterfowl habitats become restricted during the dry winters. Nevertheless, some tropical species, such as the white-faced duck, are expanding their ranges into more temperate regions where summer habitats are available, thus increasing pressure on overwintering habitats. The subtropical Pongolo River floodplain is an important overwintering area for a diverse water-fowl community that includes 13 of the 16 species that breed in South Africa and one of the few regular migrants. Historical evidence suggests that numbers of white-faced duck, which represent over 70% of the floodplain community, have increased 10-fold over the last two decades. An abundant, nutritious food (Potamogeton crispus turions) attracts waterfowl to the Pongolo floodplain during winter and an increase in bird fat reserves suggests that they leave for summer breeding grounds in good condition. Unseasonal flood releases from an upstream reservoir may cause low food supplies in late spring before the onset of the summer rainy season when breeding habitats become available. This study emphasizes the need for a better understanding of the role of winter habitats in maintaining waterfowl populations.