Spring body condition, moult status, diet and behaviour of white-faced whistling ducks (Dendrocygna viduata) in northern South Africa

Abstract

Many white-faced whistling ducks (Dendrocygna viduata) have responded to European colonization by overwintering on irrigation and stock-watering ponds in the semi-arid interior of South Africa. I studied the body condition, diet, behaviour and moult intensity of whitefaced whistling ducks prior to departure for breeding areas during spring 1995. Other than higher protein levels in immature males than immature females, there were no sexual differences in body mass or levels of lipid, protein, or ash in adults or immatures. Adults were heavier than immatures and had higher levels of ash. There were no sex- or age-related differences in the proportion of individual food items consumed, 96.6% of which was maize. By foraging on neighbouring agricultural fields, birds were able to spend large portions (80%) of the day/night in comfort-related activities (preen, loaf, sleep) and little time foraging (8.8%) while on ponds. There were no sex- or age-related differences in overall moult intensity score or intensity of moult in 20 feather areas. With exception of primaries and secondaries, birds were moulting moderately to heavily in all feather regions. Agricultural ponds permit whitefaced whistling ducks to overwinter close to breeding areas, while the high availability and energy content of maize enables them to attain higher spring fat levels than birds that overwinter on traditional sites closer to the coast. Intensive agriculture has probably contributed to the population increase and range expansion of white-faced whistling ducks in South Africa.

Keywords: agriculture, Dendrocygna viduata, semi-arid, South Africa, white-faced whistling ducks