Use of artificial tree hollows by Australian birds and bats

Abstract

Artificial tree hollows (nest or roost boxes) may be of considerable importance to the conservation and management of Australian hollow-using birds and microbats. This is suggested by recognition that the rate of collapse of hollow-bearing trees may exceed replacement in some landscapes. We review the published literature to synthesise current information on the use of artificial hollows by Australian birds and bats, and to provide guidance to future research and management. The use of artificial hollows has been documented in some detail for 15 native bird and eight microbat species. A range of hollow designs has been employed but there is a limited understanding of favoured designs. General designs (e.g. front-entry plywood boxes) have been used extensively by some species and should continue to be used until more effective designs are identified. Species tend to use artificial hollows that have entrance sizes just sufficient for their body size, and this should guide hollow design. Competitive interactions with a range of non-target species (native and non-native) may have a pronounced influence on artificial hollow use and must be considered in any management program involving artificial hollows. We highlight some design elements that may reduce interference by non-target species. Temperature inside artificial hollows may have a particular influence on their use by bats due to the role of microclimate in bat thermoregulation. Trials are needed to investigate this factor and to inform general approaches to positioning of artificial hollows. Several distinct management uses exist for artificial hollows, including assisting threatened species recovery, e.g. Kangaroo Island glossy black-cockatoo (Calyptorhynchus lathami halmaturinus) and orange-bellied parrot (Neophema chrysogaster). Artificial hollows offer an interim solution to hollow shortage but their full potential will only be realised when preferences for different designs are better understood. This will require a commitment to monitoring and should be conducted in an adaptive management context. Increased knowledge of the use of artificial hollows by Australian birds and bats should be of global relevance to the management of hollow-using species because it provides an independent test of ideas and strengthens any generalisations.