Les Anatidés hivernants dans le delta intérieur du Niger (Mali)

The 35,000-km2 Inner Niger Delta, Mali, is one of the three vast wetlands in West Africa used as wintering sites by anatids, Anatidae. Aerial counts over 103-112 quadrats (18 km x 18 km), covering 84-90% of potentially interesting wetlands for waterbirds, were made in January 1999, 2000 and 2001. The total amounts of anatids were estimated at 269,000 in 1999, 711,000 in 2000 and 1,000,000 in 2001. Among the six Ethiopian species recorded (n = 10,634 in 1999, 65,195 in 2000 and 77,587 in 2001), white-faced whistling- ducks, Dendrocygna viduata, were the most numerous (73-91%), followed by spur-winged geese, Plectropterus gambensis (4-23%) and fulvous whistling-ducks, Dendrocygna bicolor (1-12%). Among the four recorded palearctic species (n =258,030 in 1999, 645,550 in 2000 and 922,655 in 2001), garganeys Anas querquedula, were the most numerous ones (80-81%), followed by pintails, Anas acuta (16-18%). The other Ethiopian species (Egyptian goose Alopochen aegyptiacus, knob-billed duck Sarkidiornis melanotos, African pygmy-goose Nettapus auritus) and palearctic species (northern shoveler, Anas clypeata, ferruginous duck, Aythya nyroca) represented a small percentage of all counted birds. Among the 1,380 censused anatid flocks, 44% were single-species and 56% multi-species flocks. Ferruginous duck and knob-billed duck were the species most inclined to find themselves staging together with several other ones. Considering the changes in anatid numbers from 1972 to 2001, it seems that, independently of the quality of the counts and the degree of inundation of the delta, for a majority of the species there were good years (1978, 2000 and 2001) and bad years (1972, 1974 and 1999). The 1999-2001 counts confirm the importance of the Inner Niger Delta as a wintering area for anatids since we estimated that its anatid population represents 10-50% of the West African wintering anatid populations, except for the ferruginous duck (50-100%), and the Egyptian goose and northern shoveler that were marginal. The birds’ dispersion shows how important it is that counts be made in the whole delta and not only in a few sampling sectors, and that simultaneous monitoring be conducted once in the three large basins (Inner Niger Delta, Senegal Delta and Lake Tchad) at the least, and maybe in Sudan, to apprehend the changes in the numbers of wintering anatids