The status of the Great White Pelican in Africa in the 1980s is reviewed. During this period the size of the colony of Pelecanus onocrotalus located on the Mauritanian coast at the banc d’Arguin increased ten-fold owing to an influx of birds coming from newly installed colonies in Senegal. Great White pelicans are absent from the Banc d’Arguin from February to June. The first birds install on the Banc in July, coinciding with the arrival of warm waters from the Gulf of Guinea. The pelicans lay their eggs in successive waves from mid-August to the end of November. The clutch size is unusually low for the species (mean 1.25 eggs/nest). There is a positive relation between clutch size and the size of the breeding cohort (r= 0.87, P< 0.01). Heavy mortality of chicks of all ages is recorded from mid-December onwards, together with a massive departure of adults towards the south. This mortality appears to be due to the upwelling of cold water which displaces the warm water towards the south : this hypothesis was tested from supporting evidence. Observations on the composition of chick regurgitates, the behaviour of adults on the foraging grounds (both during the day and at night, but exclusively at low tide) and the timing of breeding of other fish-eating bird species confirmed this hypothesis.