Predispersal Range, Behaviour and Use of Exotic Roost-trees by a Subadult Powerful Owl 'Ninox strenua'

A subadult Powerful Owl Ninox strenua was radio-tracked on 21 nights, over 4 weeks, in order to assess the possible impacts of habitat restoration involving removal of weed-tree roosts at Mt Evelyn, Victoria, in 2003. The Owl was found to be at least partly dependent on its parents until 7-8 months old (5-6 months post-fledging). This bird ranged and roosted in an area of 90 ha over a period of 4 weeks before dispersing from its natal territory. It often roosted alone during the day, but responded at night when its parents called by meeting them and begging for food. The home-range increased suddenly to 550 ha over three nights preceding its apparent dispersal away from the adults' territory. The radio-tagged Owl was found roosting in Sweet Pittosporum Pittosporum undulatum (18 times), Monterey Pine Pinus radiata (4 times), White Willow Salix alba (4 times) and Hazel Pomaderris Pomaderris aspera (once). Only the last is indigenous to the area, and the other species are considered to be weed trees.