Rohan J. Bilney

A total of 783 dietary items from a Sooty Owl Tyto tenebricosa tenebricosa with suspected partial xanthochromism (yellow plumage colouration) was identified from Yarrangobilly Caves, NSW. Observations of the owl at the cave and collection of feathers suggest that prey items accumulated between 2011 and 2018. A total of 12 mammal species was detected in the diet, with the Bush Rat Rattus fuscipes, Agile Antechinus Antechinus agilis, Sugar Glider Petaurus breviceps and Rabbit Oryctolagus cuniculus dominating. The diet also included three threatened species, the Eastern Pygmy Possum Cercartetus nanus, Smoky Mouse Pseudomys fumeus and Broad-toothed Rat Mastacomys fuscus. The diversity of prey identified in the diet contrasts markedly with that found in studies of subfossil deposits from the area, supporting evidence of extensive mammal declines since European settlement.

This study reports the diet of the powerful owl (Ninox strenua) in East Gippsland, from a dataset of 2009 vertebrate prey items collected from 53 sites. Mammals dominated the diet at all sites, but birds were also consumed regularly. The greater glider (Petauroides volans) was the dominant dietary item across the region in terms of both frequency of consumption and biomass contribution. There was geographical dietary variation between coastal and foothill forest sites, with the sugar glider (Petaurus breviceps) and birds consumed more frequently in foothill forests, whereas the common ringtail possum (Pseudocheirus peregrinus) was frequently consumed only in coastal forests. Typically, a higher percentage of powerful owl diet comprised birds closer to cleared land. The dietary reliance upon hollow-dependent mammals in foothill forests (averaging >70%) is of conservation concern, especially when non-hollow-dependent prey are rare. Forest management activities, especially logging, that reduce densities of hollow-bearing trees in the landscape are therefore likely to decrease the long-term carrying capacity of the landscape for the powerful owl.