Inferring the extinction status of the South Island Kōkako from sighting records

The South Island Kōkako (Callaeas cinerea) is an endemic New Zealand bird species with an uncertain extinction status. Declared extinct in 2007, the species was re-evaluated as extant in 2013, following a single verified sighting. There have been no verified sightings in the years since, but large numbers of unverified sightings. In this paper, we apply statistical methods to this sighting timeseries to evaluate whether a population of the species continues to exist on the South Island and Stewart Island. Our findings suggest that there is still a reasonable probability (48%) that the species is still extant. However, we also find that it is not improbable that all recent sightings are false positives. These results raise important questions about the reliability of current extinction models in the presence of nonstationary sighting processes, and their implications for the allocation of sparse conservation funding.