Return of the Fauna: Brown Treecreeper Reintroduction in Eucalypt Woodland

Abstract

Species reintroductions have become an increasingly prevalent conservation tool to combat species decline and extinction. Reintroduction programs aspire to re-establish a self-sustaining population of a species in an area where the species was formally extant. This thesis contributes to conserving a threatened species, the Brown Treecreeper (Climacteris picumnus), through an experimental reintroduction, and also informs the effectiveness of restoration treatments in the nature reserves where reintroduction occurred. I first reviewed Australian species relocations published within peer-reviewed literature. I identified key areas where improvements to relocation programs can be implemented, including: (1) integrating an experimental framework; (2) strategic, long-term monitoring; and (3) criteria for success. These findings contributed to ensuring that the Brown Treecreeper reintroduction was conducted to a high standard. Seven Brown Treecreeper social groups (43 individuals) were reintroduced into Mulligans Flat and Goorooyarroo Nature Reserves in the Australian Capital Territory in south-eastern Australia in November 2009. The reserves are the location of a large-scale experimental restoration project. Restoration treatments include the addition of coarse woody debris, maintenance of variation in ground vegetation cover, and the installation of nest boxes. At release, 18 Brown Treecreepers were fitted with radio-transmitters to assist daily monitoring until February 2010. Survival of individuals one year post-release (15% confirmed adult survival) failed to meet the pre-determined criteria for success (40% adult survival). Therefore, the reintroduction program cannot be deemed as successful. I examined the influence of experimental restoration treatments on Brown Treecreeper movement, habitat use and behaviour. This enabled assessment of restoration effectiveness and the suitability of using existing ecological knowledge to inform reintroduction outcomes and post-release behaviour. Brown Treecreeper movement characteristics were not influenced by habitat quality. Social groups showed a preference for settling in areas with low levels of ground vegetation cover, which improves ground foraging efficiency. However, the overall influence of habitat quality on settlement was less than predicted. The addition of coarse woody debris benefited the species by increasing the probability of foraging on the ground or on logs. The amount of ground foraging by reintroduced Brown Treecreepers was less than has been observed in other populations. This highlights the requirement for further ground layer management including promoting cryptogamic crust development, improving leaf litter levels, and controlling grazing by native herbivores. I analysed the influences on the apparently high predation rate of Brown Treecreepers. There were fewer refuges in the reintroduction reserves compared to areas where birds were sourced, indicating a reduced ability to escape from predators. The reintroduction reserves also had lower quality ground foraging habitat quality. However, reintroduced individuals dispersed extensively and settled in higher quality habitat more closely resembling the source site. Results from this thesis provide crucial information regarding restoration effectiveness and Brown Treecreeper ecology. Whilst some restoration treatments were successful, there was insufficient improvement to support the species. Complete woodland restoration may require incorporation of finer details and more spatial variation and innovative methods than ordinarily considered. Unexpected results from this study also reinforce the importance of integrating an experimental framework to inform reintroduction biology.