Field methods to identify Palm Cockatoo nest hollows

Abstract

Within Australia, the iconic Palm Cockatoo Probosciger arterrimus macgillivrayi occurs only on the Cape York Peninsula, Queensland, has recently been listed as Endangered, and requires large, old hollow-bearing trees for nesting. Surveys for these trees are crucial for management purposes. Typical surveys rely on following auditory (vocalisations) and visual (sightings) cues to determine the presence of birds or nests. However, nesting hollows can easily be inadvertently overlooked during such surveys because of false absences caused by biennial nesting, decreased vocal activity during nesting, and silent flushing from active nests when approached. We developed a systematic, grid-based transect methodology that maximises the likelihood of identifying potential, used, and confirmed Palm Cockatoo nest hollows and this has been implemented on western Cape York Peninsula since 2015. This method does not rely on bird presence at the time of surveys, but instead relies on multiple, specific signs of recent Palm Cockatoo nesting activity, to the exclusion of other large, sympatric parrots. We tested this method on novice observers and found that it enabled them to rapidly learn how to detect Palm Cockatoo hollows in the landscape. Thus, for ecological surveys on Cape York Peninsula, we propose that this method should supersede previous auditory/ visual surveys to identify Palm Cockatoo nesting sites, and we hope that this improves the conservation of this species in Australia.