SEABIRDS OF THE SENEGAL UPWELLING AND ADJACENT WATERS

Seabird distributions were observed off Senegal during the upwelling season there, in February-March 1976, and are interpreted against an oceanographic background. Gannets Sula bassana , Pomarine Skuas Stercorarius pomarinus , Great Skuas Catharacta skua , Lesser Black-backed Gulls Larus fuscus , Black-headed Gulls L. ridibundus , Sandwich Terns Sterna sandvicensis and Royal Terns S. maxima were the dominant species on the shelf and slope adjacent to the inshore upwelling zone. Grey Phalaropes Phalaropus fulicarius were the only seabirds associated with an oceanic 'front' farther offshore; it is suggested that this and similar boundary zones are important feeding areas during the pelagic phase of this species' annual cycle.
Leach's Storm-Petrels Oceanodroma leucorhoa were seen east to 20W, but the predominant storm-petrel of the waters between 23W and the continental slope was the Madeiran O. castro. It is suggested that the hatching period of Madeiran Storm-Petrels on the Cape Verde Islands is timed to take advantage of the arrival there of young fish in the surface waters, spawned off the African coast and drifted offshore. However Madeiran Storm-Petrels make no direct use of the coastal upwelling; nor do Little Shearwaters Puffinus assimilis or White-faced Storm-Petrels Pelagodroma marina , the other winter-breeding Cape Verdes seabirds, which probably feed close to the Islands.
The Senegal upwelling is underexploited by seabirds, in contrast to comparable upwelling systems elsewhere. It is suggested that this is due to the seasonal timing of the upwelling, the scarcity of secure nest-sites for breeding seabirds, and the competing attractions of the Benguela upwelling in the South Atlantic.