Controlling the flood in the Senegal Delta: do waterfowl populations adapt to their new environment?

Abstract

Triplet, P. & Yésou, P. 2000. Controlling the flood in the Senegal Delta: do waterfowl populations adapt to their new environment? Ostrich 71 (1 & 2): 106–111.

The delta of the Senegal river (320 000 ha) has been gradually dammed, mostly during the 1970–80s. From 1986, the Diama dam has stopped any backflow of salt water from the sea into most of the delta, and retains a large volume of fresh water which can be released into initially naturally flooded, but now embanked, areas, including the National Parks of Djoudj (Senegal) and Diawling (Mauritania) and other lowlands often used for agriculture, mainly rice-fields. Landscapes have been deeply modified (vegetation overgrowing in wetlands, desertification process around), sometimes in a provisionally positive way (creation or development of flooded areas through irrigation or hunting management). The Anatidae overwintering in the delta have been censused since 1972: we analyse these census data, with emphasis on the periods 1972–1976 and 1989–1996 (when census methodology and coverage were similar), in order to define how Anatidae have adapted to the new environmental conditions.

Three Afrotropical and two Palearctic species are holding on, in spite of marked yearly variations and sometimes a loss of habitat quality (Fulvous Whistling Duck Dendrocygna bicolor. White-faced Whistling Duck D. viduata, Egyptian Goose Alopochen aegyptiacus. Northern Pintail Anas acuta, Garganey A. querquedula), two Palearctic species showed significant but not fully explained changes in numbers (Northern Shoveler Anas clypeata increasing, Common Teal A. crecca almost disappearing), and numbers of two Afrotropical species decreased following the environmental modifications (Spur-winged Goose Plectropterus gambensis, and Comb Duck Sarkidiornis melanotos even more markedly).

In order to maintain or develop conditions favourable to these bird populations, it is necessary to supply the managers of protected areas with the resources needed to implement this aim. Also, the whole lower valley of the Senegal River (including the Lake of Aleg in Mauritania) must be taken into account in conservation measures, including non-protected areas potentially favourable to waterfowl. Such a conservation programme implies the co-operation of national and international bodies related to both nature conservation and wetland development.