3. BIRD POPULATION STUDIES

Pritton, P. L. &; Erown, L. H. 1974. The status and breeding behaviour of East African Lari. Ostrich 45: 63–82.

This paper summarises and clarifies the East African status of the 24 Lari recorded, especially the breeding of eight terns, two gulls and the African Skimmer.

Breeding seasons are discussed fully. The season for terns and the Sooty Gull on offshore coral islets in northern Kenya, mainly in July-August when the islands are least accessible, is probably a man-orientated defence mechanism rather than a response to food availability. Inland, the Greyheaded Gull breeds in comparatively inaccessible sites, on islands in large lakes, generally during the main rains. Here it is believed more likely that food supplies are influenced by the onset of rains, and that the inaccessibility of sites at that season is a secondary advantage. Whiskered Tern breeding is mainly initiated by the onset of rains and the consequent creation of suitable habitat. It is uncertain what factors influence Skimmers to breed mainly in April-May at Lake Rudolf, Kenya. Elsewhere, Skimmers breed on exposed sandbanks along large rivers during the dry season.

Further miscellaneous data, including clutch size and nest sites. are given for all species. The highly erratic breeding of up to 8 000 pairs of Roseate Terns on the Kenya coast is noteworthy. It seems likely that only a proportion of the total adult population breeds in any one year.

The seasonal status and movements of both breeding and non-breeding species is described. In particular, it is shown that Skimmers breeding during the dry season in the southern tropics spend the off-season in the western rift, regularly north to the Equator and beyond, on the Nile in western Uganda. Lake Rudolf breeders probably wander widely in Kenya, occasionally to the coast, northern Tanzania and eastern Uganda.