Spatial ecology informs reintroduction tactics for warabin (Burhinus grallarius;bush stone-curlew)

Abstract

Reintroduction is an important conservation intervention used to restore species and their ecological functions within their former range. Reintroduction success relies on the appropriate selection of tactics and strategies tailored to the species and recipient ecosystem; however, sufficient ecological knowledge is not always available, particularly for poorly studied, cryptic and refugee species. This challenge can be overcome by using adaptive management, a framework which enables ‘learning by doing’. This thesis provides a case-study using an initial reintroduction to inform tactic selection for future translocations. Warabin (Burhinus grallarius) have declined substantially in southern Australia due to habitat loss and predation by feral predators (largely foxes, Vulpes vulpes) and now occupy a subset of their former niche. They have been successfully reintroduced to a fenced reserve, Mulligans Flat Woodland Sanctuary (MFWS), which provides an opportunity to assess their habitat requirements and movement behaviours. Founders and residents (founders released in previous years and their offspring) were fitted with GPS backpacks. Founders were wing-clipped to prevent dispersal over the fence. GPS data was used to calculate home-ranges, dispersal, and to develop a maximum entropy (maxent) species distribution model of warabin habitat use. Warabin habitats were partitioned into roosting habitat, characterised by cover (30-40% overstory, >5% understory and hill slopes), and foraging habitat, characterised by food-related features (live green vegetation, deep soils and proximity to water). Roosting habitat required more specialised features than foraging habitat, and these habitat features can be remotely-sensed to select future sites for warabin release. Founders were more likely to survive to 3-months if they moved further away from the release site (but remained within MFWS), and had decreasing home-range sizes over time. Whilst founders stayed in the sanctuary, residents flew outside the sanctuary to forage on 50% of days, demonstrating that they can use novel-habitat (agricultural land and urban areas) and coexist with foxes. The estimated carrying-capacity for MFWS is 90-100 pairs, and when this carrying-capacity is reached, MFWS could be used as a source population for future translocations. This study demonstrated that an initial translocation can be used to gather critical ecological knowledge to inform future attempts, and species distribution modelling can aid this process. Rather than waiting until ‘enough’ is known about a species or recipient ecosystem, embarking on a translocation and applying learnings ‘on the fly’ can improve reintroduction outcomes. By using an adaptive management framework in such conservation projects this study has shown the potential to increase success in reversing loss of species and their functions and restore biodiversity.