Red fox predation dominates threats to the Southern Squatter Pigeon: evidence from contemporary and hindcasted distribution models

Understanding the relative influence of individual threats on species decline is essential for effective conservation planning. This is particularly challenging for species that declined historically, as early losses leave limited records from which to infer past distributions. The southern subspecies of the Squatter Pigeon (Geophaps scripta scripta), a granivorous bird from eastern Australia, experienced a substantial range contraction in the early 1900s. Reported causes of decline include land clearing, habitat degradation and feral predators; however, the relative importance of these threats has not been quantified. To address this gap, we developed an ensemble species distribution model (SDM) to evaluate the influence of environmental variables and threatening processes on the contemporary relative likelihood of occurrence (RLO) of the Southern Squatter Pigeon. We then hindcasted historical habitat extent using environmental conditions and threat distributions prior to European colonisation to infer how the subspecies’ range may have contracted. Contemporary suitable habitat was estimated at approximately 359,500 km2, primarily in central and northern Queensland. Hindcasting estimated a historical habitat extent of approximately 688,000 km2, representing an approximate 48% decline in RLO. Habitat losses were concentrated in inland New South Wales and southern Queensland. Among threatening processes, red fox density had the strongest negative association with Southern Squatter Pigeon RLO. Cat density was a comparatively weak negative predictor of Southern Squatter Pigeon RLO, and habitat condition showed only a minor influence. Overall, these findings identify the red fox as the primary threat to the Southern Squatter Pigeon.