Long-term loss of Carnaby’s cockatoo Zanda latirostris nest hollow resources in the Western Australian Wheatbelt 1996–2020

Context. Nest hollow resources provided by native eucalypts in southwest Western Australia are a diminishing resource. Aims. We investigated the change in nest hollow availability in two common species of eucalypts used by Carnaby’s cockatoo (Zanda latirostris) across multiple land tenure types over a 25-years period in the northern wheatbelt of Western Australia. Methods. Changes due to natural and anthropogenic causes in the persistence, canopy health and nest viability in wandoo (Eucalyptus wandoo) and salmon gum (E. salmonophloia) nest trees across four land tenure types were monitored after a 22-year interval. A proof-of-concept trial to repair unviable nest hollows was conducted on a limited sample of salmon gum trees. Key results. The loss of nest trees was consistent across land tenures and tree species. Mean annual rate of loss of trees was 29-242% higher than species-specific rates previously reported in the literature. Tree canopy health was unchanged in 33-45% of trees, while 43-53% of dead standing nest trees were lost over 22 years. Conclusions. The increased rate of loss recorded, along with the decline in canopy health of living trees indicates a major collapse in eucalypt woodland nest availability can be expected in the northern wheatbelt over the next 50-70 years. Implications. Maintenance of eucalypt woodland nest hollow resources will depend on provision of artificial nest hollows, repairs to existing viable and currently unviable nest hollows, coupled with an urgent need to establish new woodlands through targeted planting programs.