Conservation value of solar salt ponds in coastal tropical eastern Australia to waterbirds and migratory shorebirds

Some human-altered habitats such as saltfields support significant numbers of shorebirds and waterbirds, but their values in tropical eastern Australia are poorly understood. With the continuing loss of shorebird habitats in the East Asian-Australasian Flyway, identification of important habitats and management is important for their conservation. The habitat value of two saltfields associated with the Fitzroy River estuary, Queensland (23.52°S, 150.86°E) was evaluated by monthly surveys over 33 months and by comparison to previous surveys of nearby natural wetlands. Saltfields supported as many waterbirds and species as freshwater and naturally saline lagoons. Numbers of migratory shorebirds peaked during the southern migration period (September to November), when wetlands in tropical northern Australia are at their lowest extent, thus elevating the conservation value of tropical saltfields to shorebirds. Sharp-tailed Sandpipers were regularly present in numbers exceeding international levels for staging, while Red-necked Stints were just below the staging criterion. Salinity regime was found to influence waterbird communities associated with saltfield pools: piscivores dominating metasaline pools, and shorebirds hypersaline pools. A seasonal pattern of occurrence occurred in some guilds with greatest numbers in the drier months (cormorants, pelicans, ducks and egrets, all significantly negatively correlated with the previous month's rainfall), most of which bred in nearby natural wetlands during the wet season. Furthermore, cormorants were abundant in the saltfields and fluctuated less compared with natural lagoons during the critical drier months. Overall, saltfields are an integral component of the ecology of the landscape, providing complementary resources to that of the natural wetlands.