Scale-dependent patterns of abundance and habitat use by cormorants in arid Australia and the importance of nomadism

Abstract

We investigated the ways in which cormorants (Phalacrocorax spp.) acquire behavioural cues from unpredictable habitats in arid Australia, using 10 years of temporal data on abundance at one wetland, fine-grained habitat and microhabitat use at two wetlands, and broad-scale spatial data from aerial surveys across north-west New South Wales. Abundances were highly variable and cormorants were aggregated at every temporal and spatial scale of observation. Cormorants were associated with short-term patches of food, and apparently travel frequently in a quest for newly formed patches. Movements and abundance of cormorants are linked to boom periods of their prey, and, like many Australian waterbirds, cormorants would benefit from improved water management practices.