Rapid and recent range collapse of Australia's Red Goshawk Erythrotriorchis radiatus

Australia's Red Goshawk (Erythrotriorchis radiatus) is a taxonomically distinct raptor endemic to the tropics and sub-tropics of eastern and northern Australia, and the Australian mainland's rarest bird of prey. Classified as Vulnerable when legislation was first enacted in 1992, the species' status and distribution remain unclear, and it is possibly declining based on limited surveys. However, no comprehensive analysis of its range-wide population trends has ever been undertaken, creating a knowledge gap which potentially delays urgent conservation management. Here, we bridge that knowledge gap. We compile a comprehensive dataset of 1,679 occurrence records spanning the species' historical range, develop a novel method that overcomes reporting biases centred around nest locations, then identify population trends between 1978 and 2020 at national, state, and regional scales. Our results suggest that the species has declined significantly across eastern Australia and is likely locally extinct in many regions. We estimate the Red Goshawk has disappeared from 34% of its breeding range over the last four decades, and probably persists at extremely low density, if at all, over an additional 29.7% of its breeding range. These results demonstrate the species' declining population trajectory at multiple scales for the first time and provide further evidence for its up listing under Australian federal legislation to Endangered, using IUCN Red List criterion C2a(ii): small population size and decline. We recommend population surveys and monitoring coupled with targeted research to better understand population trajectories and determine which threats are driving this unique species' decline.