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

We captured 2 postbreeding white-faced whistling ducks (Dendrocygna vi duata) on the Nyl River floodplain, South Africa, on 22 April 1995 and fitted (backpack) with 30-g satellite platform transmitter terminals (PTTs) using a teflon-harnessing technique that was perfected in capti vity. Both birds relocated less than 85 km to agricultural regions tha t are heavily irrigated throughout winter. While on, and adjacent to t he floodplain breeding area, distance between successive weekly locati ons for the 2 birds was 17.0 and 21.0 km. After birds relocated to agr icultural 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-s eason (winter) availability of native seeds is a major motivation for birds to vacate the floodplain, because stock-watering ponds provide a quatic habitats on and near the floodplain throughout winter. Before E uropean settlement and provision of permanent water-bodies and agricul tural grains, practically all semiarid breeding white-faced whistling ducks probably would have been displaced to more subtropical and river ine regions where water and native seeds are more readily available du ring winter. Remaining near breeding areas liberates birds from the in creased 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 Mill partially offset the effects o f extensive wetland drainage and destruction in South Africa.