SATELLITE TRACKING OF WHITE-FACED WHISTLING DUCKS IN A SEMIARID REGION OF SOUTH AFRICA

We captured 2 postbreeding white-faced whistling ducks (Dendrocygna viduata) on the Nyl River floodplain, South Africa, on 22 April 1995 and fitted (backpack) with 30-g satellite platform transmitter ter- minals (PTTs) using a teflon-harnessing technique that was perfected in captivity. Both birds relocated less than 85 km to agricultural regions that are heavily irrigated throughout winter. While on, and adjacent to the floodplain breeding area, distance between successive weekly locations for the 2 birds was 17.0 and 21.0 km. After birds relocated to agricultural areas, distances dropped to 4.8 and 6.2 km, probably due to a high availability of agricultural grains. We suggest that a low dry-season (winter) availability of native seeds is a major motivation for birds to vacate the floodplain, because stock-watering ponds provide aquatic habitats on and near the floodplain throughout winter. Before European settlement and provision of permanent water- bodies and agricultural grains, practically all semiarid breeding white-faced whistling ducks probably would have been displaced to more subtropical and riverine regions where water and native seeds are more readily available during winter. Remaining near breeding areas liberates birds from the increased energetic costs and possibly higher mortality of a relatively long migration. Incentives and guidance should be provided to farmers to encourage proper construction, management, and enhancement of farm ponds for waterfowl. This practice will partially offset the effects of extensive wetland drainage and destruction in South Africa. J. WILDL. MANAGE. 61(4):1208-1213