Habitat preference and distribution of the Powerful Owl (Ninox strenua) on the Mornington Peninsula, Victoria

Identifying the distribution of threatened fauna is fundamental to allocating scant resources for conservation purposes. Predictive habitat modelling based on environmental data from species records is currently used to inform conservation management but research is needed to verify the reliability of those Species Distribution Models (SDMs). This study focused on the threatened Powerful Owl Ninox strenua, in a region that lacked historical records but where SDMs predicted suitable habitat was available. This study was aimed at ground truthing the existing habitat suitability model for the Powerful Owl while providing new data to improve the spatial comprehensiveness of the model. The Victorian state-wide habitat suitability model for the Powerful Owl was used to stratify the study area (Momington Peninsula) into three classifications of habitat suitability (Low, Low- Medium and Medium). Forty sites were randomly selected comprising 13 low suitability, 13 low-medium habitat suitability, and 14 medium habitat suitability sites. Powerful Owl call-playback was undertaken a total of 112 times with each site surveyed at least once. A subset of 6 sites per habitat suitability class were surveyed 5 times to provide an estimate of detection probability. Repeat surveys at the same site were important to improve the probability of determining if Powerful Owls were present at a site (one to four visits increased overall detection from 33 per cent to 80 per cent). A Bayesian state-space modelling approach was used to estimate the occupancy of Powerful Owls as a function of habitat suitability class and prey abundance. Detectability was modelled using survey conditions (wind speed). This study shows that existing state-wide models of Powerful Owl habitat suitability reliably predict the occupancy of this species on the Momington Peninsula. Powerful Owls were found at a higher proportion of Medium (72%) and Low-Medium sites (66%), with lower levels of occupancy in Low habitat suitability sites (24%). This study provides new information regarding the distribution and habitat preference of the Powerful Owl on the Momington Peninsula, while highlighting the value of predictive species distribution modelling for wildlife conservation and managemen