The status of breeding seabirds and herons at Ashmore Reef, off the Kimberley Coast, Australia

Ashmore Reef is situated on the edge of Sahul Shelf, off the Kimberley coast, Australia. Surveys in 2010 indicate the three small islands within Ashmore Reef support approximately 100,000 breeding seabirds of 16 species and four heron species on an annual basis. That such a diversity and abundance of tropical seabirds utilize a total land area of just 55 ha for breeding purposes is exceptional in an international context. In this paper we review population sizes of breeding seabirds and herons at Ashmore Reef. Bayesian change-point models applied to count data spanning a 60 year period demonstrate that populations of breeding seabirds have increased at this location. Large ground-nesting seabirds display positive step changes in population size since the late 1980s whilst populations of shrub-nesting congeners display similar step changes since the late 1990s. We discuss the potential reasons for these abrupt population increases.