Breeding Biology of the Bridled Tern Sterna anaethetus

Abstract

Features of breeding Bridled Terns can be considered as either anti-predator or other adaptations. Each anti-predator feature acting by itself or with others can decrease the likelihood of gulls preying on eggs and/or chicks. Anti-predator features include nesting under cover, dispersion of nests, cryptic colour of eggs and chicks, behaviour of ohicks and adults, defeacating away from the nest and fast initial growth of chicks. However, other features can increase the likelihood of gulls preying on young. These include asynchronous laying and hatching and not removing egg shells from nests.

Breeding success of Bridled Terns at One Tree Island, Great Barrier Reef was high because: (1) predation on their eggs and chicks was lower than on those of other terns, (2) their ability to fast for longer periods than, for example, Crested Tern Sterna bergii chicks buffered them from the effects of cyclonic weather.

Growth rate of Bridled chicks may depend on the ability of, and the effort made by, their parents to transport food to them as well as the nutrient composition of their diet. We suggest that dietary differences are responsible for dif- ferences in the timing of adults' moulting in the Seychelles and Australia.