Habitat use by Seychelles sooty terns Sterna fuscata and implications for colony management

The relationship between sooty tern Sterna fuscata nest densities and vegetation characteristics of the breeding colonies was investigated on four islands in the Seychelles. Nest densities were greatest in areas with a vegetation cover of 30-50%, and areas that provided these conditions were generally dominated by pourpier Portulaca oleracea. On Aride Island, sooty terns nested at low density under an enclosed tree canopy but on the other islands nests were generally in the open, among sparse vegetation. On Desnoeufs Island, where eggs are harvested commercially for human consumption, sooty terns avoided nesting in dense areas of epi bleu Stachytarpheta jamaicensis, an introduced plant whose success on the island may be related to egg exploitation. Management of colony vegetation, especially the control of introduced aggressive species, and the encouragement of optimum conditions for nesting, could increase the numbers of nesting sooty terns and their reproductive output, helping to buffer them against adverse effects of human activity. Appropriate protection of sooty tern colonies can also benefit rarer and more vulnerable seabirds and turtles that share nesting islands.