Notes on the biology of the threatened Island Thrush Turdus poliocephalus xanthopus in New Caledonia

Three subspecies of Island Thrush Turdus poliocephalus were historically found in New Caledonia. All these subspecies were considered extinct until 1978, when T. p. xanthopus was rediscovered on two small islands, Neba (∼ 3.5 km²) and Yande (∼ 13 km²). On Neba, we estimated the population at 44–58 individuals. This Island Thrush population is dependent on the coastal forest, the richest habitat for invertebrates. However, the coastal forest habitat has been degraded in quality and extent. The Island Thrush forages in the litter by removing leaves with its bill. Fruits (diameter < 10 mm), picked from trees and swallowed whole, are also a significant component of its diet. Neba and Yande are currently free of two nest predator species, the black rat Rattus rattus and the New Caledonian Crow Corvus moneduloides. On Neba, a low breeding success rate of 15.4% was found. To ensure conservation of these relict thrush populations, two actions at least should be implemented: setting up a biosecurity programme to keep islands free of black rats and increasing the area of coastal forest. The latter could be done by cutting down coconut trees in abandoned groves and planting tree species used by the Island Thrush to provide shade, fruits, good leaf litter, and nest support.