The influence of early age at breeding on reproductive parameters of tropical Roseate Terns

At Aride Island, Seychelles, western Indian Ocean, over a period of five years (2002–2006), early-age (2–5 years) Roseate Terns Sterna dougallii nested in more concealed sites than older-age (6–7 years) birds, possibly because of a relatively lower competitive ability. Fledging success and breeding productivity were higher for older birds, but clutch size, laying date and egg volume were most influenced by marine productivity (the concentration of chlorophyll a in adjacent seas, which was assumed to reflect feeding conditions) or by an interaction between marine productivity and age. Older birds bred earlier in years when food availability was greater, but younger birds did not do so. Annual variations in environmental conditions should be taken into account when examining the effect of age on the reproductive parameters of tropical Roseate Terns.