Avian nest predation in Australian temperate forest and woodland: a review

Abstract

Many forest and woodland birds are threatened by landscape modifications and predation, particularly nest predation. Nest predation affects a critical stage in avian life histories, which impacts the recruitment of new generations of adult birds. This review discusses the main issues in nest predation research in Australia: mesopredators, the use of artificial nests, ‘edge-effects’, the identification and role of nest predators and the responses of their prey. One conservation strategy is to selectively remove introduced mesopredators, but mesopredators iteratively replace one another, so the net benefit may be negligible. Authors have questioned the utility of artificial nests: they often provide results that vary from natural nests, thus I propose they are best seen as generators of hypotheses to be tested at natural nests. Many studies investigated nest success based on the distance to the edge of the forest or woodland, with equivocal results. Yet fragment size, structure and faunal assemblage set in a more complex paradigm may better explain the presence or absence of effects at edges. There are various types of evidence used to identify nest predators. I argue that cameras are the most functional and direct observations are the most informative. A large number and variety of nest predators are reported yet reviews of nest predation call for more information on the identity and roles of nest predators, particularly on those that add predation pressure beyond what the prey might be able to sustain. The impact of nest characteristics: type, height, vegetation layer, concealment and re-nesting were found to be equivocal in relation to nest predation and in need of focussed research on phylogenetic groups and guilds present within assemblages and within the context of assemblages. A handful of research studies have looked at the possible conservation actions of culling nest-predators and placing cages around threatened birds. More such studies are needed because they provide direct information about practical interventions. Research within assemblages is required to identify and elucidate the roles of nest predators and prey responses and to generate broad and useful theories, which may better inform conservation models.