Is an Island Reserve Enough? The Decline and Fall of the White-fronted Chat (Aves: Meliphagidae) in Southern Sydney

Abstract

Ecological theory predicts that local extinction and recolonisation are normal events, but the frequency of each is likely to change as the habitat matrix between local populations becomes less suitable. Despite these predictions, local extinctions are seldom documented and there is a popular belief that nature reserves conserve biodiversity. This paper traces the decline of the White-fronted Chat (Epthianura albifrons) in the region surrounding Royal National Park and examines preliminary data on the species’ ecology and population dynamics. Although once widespread across the region White-fronted Chats are now confined to a single breeding population of approximately 20 individuals that spends much of its time as a single flock, mostly roosting, nesting and foraging within Towra Point Nature Reserve. Numbers appear to be relatively stable, but the population has lost genetic variability. In spite of a high abundance of potential nest predators, there is ongoing recruitment, with pairs nesting twice per season. The population is threatened by mangrove encroachment of salt marsh, ongoing development of the Kurnell peninsular, increased predation rates due to anthropogenically-elevated predator abundances, and demographic factors associated with small population size. The history of this species is a clear demonstration that even conservation reserves with a relatively high degree of protection from human disturbance cannot protect regional biodiversity in the absence of active management if they are isolated.