Uncertainty in assessing the viability of the Powerful Owl Ninox strenua in Victoria, Australia

Abstract

A model of the metapopulation dynamics of Powerful Owls Ninox strenua in Victoria, Australia is described, and its parameters were derived from available data. Sensitivity analysis indicates that the survival rate of adult owls is the most important parameter in the model. Because estimates of this parameter are uncertain, the predictions of the model are uncertain and unreliable. Using the best estimates of the parameters, the predicted risk of decline across Victoria is low, and local populations larger than 100 pairs have a low risk of extinction. If the lower estimates of adult and sub-adult survival are used, the abundance of Powerful Owls across Victoria is predicted to decline exponentially and faces extinction from deterministic forces. A prohibitively large field programme involving monitoring of individuallyrecognizable owls would be required to obtain an improved estimate of adult survival, and so further use of population viability analysis to assess the adequacy of particular management strategies is unlikely to be useful for this species. An alternative is to establish a long-term monitoring programme to document changes in abundance of the species in logged and unlogged landscapes.