Does the need to drink influence nest site selection in a wide-ranging threatened cockatoo?

Conserving wide-ranging species is challenging and requires an understanding of resource selection at multiple spatial scales, including how functional resources interact. Understanding this interaction is likely to be particularly important if resources are rare, such as tree hollows, or likely to change into the future under climate change, such as water availability and distribution. We examined nest selection by Karak (Calyptorhynchus banksii naso), a threatened obligate tree hollow nester endemic to south-western Australia, globally one of the regions most affected by climate change. We aimed to identify factors influencing nest hollow selection at multiple spatial scales including interactions between functional resources. We found that nest selection occurred primarily at the hollow scale, with deeper, higher hollows selected, and at the landscape scale, with hollows closer to ephemeral and permanent drink sites selected. The preference for specific types of hollows indicated that suitable hollows are likely to be scarce in the landscape and that management prescriptions need to be developed to maintain the supply of suitable hollows. Maintenance of drink sites in an area experiencing significant declines in rainfall will require more novel management prescriptions, which could potentially include the provision of artificial drink sites. Overall, our study demonstrated the importance of understanding interactions between functional resources at large spatial scales for the effective conservation of wide-ranging species.