Data on passerine migrants in West Africa published since the works of Moreau (1972) and Curry-Lindhal (19811 are reviewed and new information on wintering ranges are summarized. An important feature of West Africa as a wintering zone is the presence of the two great river basins of the Senegal and the Niger, which are responsible for the Sahel being far richer than would be expected at this latitude. This 'paradoxical' or 'green' Sahel is under the threat of agricultural developments and of increasing desertification. Conversely, Palaearctic migrants can take advantage of the new-savanna/forest mosaics and agricultural developments which have replaced the rain forest.