Sign Left by Brushtail Possums after Feeding on Bird Eggs and Chicks

Brushtail possums (Trichosurus vulpecula Kerr) have been identified as predators of adult birds, eggs and chicks. A captive possum caught and partially ate a house sparrow (Passer domesticus L.) (Morgan, 1981), and time-lapse video photography recorded wild possums eating kokako (Callaeas cinerea wilsoni Gmelin) eggs (Brown, Innes and Shorten, 1993) and chicks (Innes, Crook and Jansen, 1994). Anecdotal accounts implicated possums as predators of at least five other bird species, and feeding trials linked sign left at preyed-on kokako nests to possum feeding (Brown et al., 1993). Possum predation has direct and potentially enormous implications for protected species management on the New Zealand mainland because possums are ubiquitous and abundant (up to 25 ha in some mixed hardwood forests; Coleman, Gillman and Green, 1980). Conservation managers need to know the significance of possums as predators in different forest communities if they are to develop effective control programmes to protect species at risk. However the impacts of possums on bird populations is unknown. Determining impacts of predators on bird populations relies on linking predator identity to predation events. Predation at nests is virtually never observed (Major, 1991), therefore the sample size of evidence linking predator species to sign left after predation K.P. BROWN, H. MOLLER and J. INNES Ecosystems Consultants, P.O. Box 6161, Dunedin, New Zealand. Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand. Manaaki Whenua Landcare Research, P.O. Box 3127, Hamilton, New Zealand.