Context Apex predators are vital for maintaining ecosystem balance, yet their persistence is severely threatened by ongoing habitat loss. Landscape modification, particularly the depletion of critical breeding resources such as large tree cavities, places significant pressure on cavity-dependent species. The powerful owl (Ninox strenua), an apex predator reliant on large tree cavities for breeding, exemplifies this challenge while persisting across diverse urban, agricultural and forested landscapes in south-eastern Australia. Aims This research aimed to identify key nest tree and nest site characteristics selected by powerful owls across varied landscape types, and to determine factors influencing their breeding success. Methods We investigated powerful owl nest tree characteristics and factors influencing nest site selection at both local (50-m) and landscape (500-m) scales. Data were collected from 62 nest sites across urban, agricultural and forested landscapes in Victoria, Australia, from 2021 to 2024. Simultaneously, breeding outcome data were recorded from 89 nesting attempts within this period. Key results Powerful owls strongly favoured nest sites within areas of dense tree cover and riparian vegetation, and avoided sparsely treed or highly urbanised areas. They consistently preferred cavities within tree trunks and chose locations offering multiple alternate nesting cavities. Breeding data showed a 68.5% success rate, with proximity to multiple potential nest cavities significantly increasing the likelihood of producing two fledglings per attempt. Conclusions Our findings highlighted the critical importance of landscape composition in powerful owl nest cavity selection and highlighted how cavity availability influences breeding productivity. Implications Effective conservation strategies for powerful owls must prioritise preserving and enhancing dense tree cover, particularly near waterways. These strategies should include protecting existing cavity-bearing trees and strategically installing supplementary artificial cavities in areas where natural resources are scarce.
Lauder et al. (Tue,) studied this question.