Post‐release tracking to monitor success of black cockatoo rehabilitation in Western Australia
Bertrand Ng, Kristin Warren, Mieghan Bruce, Rebecca Vaughan‐Higgins, Jill M. Shephard, Karen Riley, Sam Rycken, Rick Dawson, Peter Mawson, Louise Hopper, Anna Le SouëfAbstract
The rehabilitation and release of injured wildlife is a common strategy employed in conservation efforts worldwide. Determining the post‐release survival and factors associated with success in rehabilitation programs is critical in assessing the effectiveness of programs and informing decision‐making throughout the rehabilitation process. To evaluate the success of the black cockatoo conservation program at Murdoch University, we analyzed hospital and rehabilitation records of 118 wild birds across 15 release events between 2015 and 2018 of the 3 threatened black cockatoo species endemic to southwest Western Australia: Carnaby's cockatoo ( Zanda latirostris ), Baudin's cockatoo ( Zanda baudinii ), and the forest red‐tailed black cockatoo ( Calyptorhynchus banksii naso ). We examined variables associated with the demographics, health, rehabilitation, and release of these birds and their associations with post‐release success. Using the results of post‐release tracking studies, we report the observed success rates in birds for which fate was known ( n = 68). Fifty‐four (79.4%) birds met our criterion for post‐release success: survival ≥4 weeks post‐release and reintegration into a wild flock. Given the limited number ( n = 14) of failure events during the study relative to the number of candidate predictors, we examined each variable individually for association with success, rather than fitting a single adjusted model. Larger resident wild flock size at the release site was associated with greater odds of successful release (OR = 5.58, 95% CI = 1.91–22.7, P = 0.005), an association that remained after accounting for clustering of birds released together (mixed‐effects logistic regression: OR = 5.55, P = 0.024). The results from this study highlight the success of this threatened species rehabilitation program and identify resident flock size as a candidate factor warranting further investigation to inform future release‐site selection.