Breeding biology of Fairy Terns on Magone Islet, New Caledonia

The threatened Fairy Tern (<i>Sternula nereis</i>) is separated into three sub-species: <i>S. n. nereis</i> in Australia, <i>S. n. davisae</i> in New Zealand and <i>S. n. exsul</i> in New Caledonia. Poor breeding success was noted in <i>S. n. exsul</i> but the factors responsible were little known. To address this knowledge gap we documented the breeding biology in a small colony on mammal-free Magone Islet off the west coast of mainland Grande-Terre. We monitored the colony daily for 215 hours over 68 days in 2018. The clutch size varied from 1–3 eggs and incubation lasted 22.5 days. Overall breeding success was 14.8% (8 chicks fledged from 54 eggs), with egg/chick mortality due to a range of factors, including egg failure/chick death, tidal flooding, avian predation and desertion. Further work is needed to determine the impact human-associated disturbance has on <i>S. n. exsul</i> breeding colonies. In the meantime, the sub-species’ vulnerable status requires restriction of human access to islands where these colonies are established.