94 J. S. Tripovich et al.


TABLE 2 List of interventions for protecting regent honeyeaters, developed during the pre-expert elicitation process from the ideas discussed in the brainstorming session (Table 1).


Avian predation Nest cages Human warden Lethal control Acoustic control (alarm calls) Mammalian predation Olfactory camouflage Acoustic control Visual and acoustic control Double-sided sticky tape Tree collars Translocate squirrel gliders Cull squirrel gliders Use lights to encourage squirrel gliders to move away from nests Extreme weather events Resource supplementation Fire management Regulatory protection Landscape management (e.g. irrigation) State-dependent decision-making for release of captive-bred individuals


Others Noisy miner control Head-starting


The IDEA protocol emphasizes anonymity in judgements, feedback, discussion and subsequent revision in a second round of elicitation (Hanea et al., 2018). In each round and for each question, experts provide a plausible lower bound, a plausible upper bound, a best estimate (lying be- tween the bounds) and the level of confidence that the truth lies between the specified lower and upper bounds, as a per cent. The questions sought estimates of the proportion of nests


that succeed, from hatching eggs through to fledging indi- vidual birds for nests of both wild and recently released (#12 months ago) birds under the base case of no pro- tection and each candidate idea, one at a time. In their responses, participants were prompted to consider the prevalence of threats collectively, the effectiveness of can- didate ideas for mitigating target threats and the residual risk of unaddressed threats. Participants were asked to ignore challenges associated with ethics approval, technical or social feasibility and cost. An example of the format of questions is shown in Table 4. We used pooled judgements in the analyses, employing


the arithmetic mean of individual judgements. The un- weightedmean of a group of experts comprising independent judgements almost always outperforms the best-performing expert within the group (Burgman, 2016).Anexample of jud- gements for a single question is shown in Fig. 1. Responses were provided by 12 anonymous experts (three workshop participants elected not to provide judgments). Plausible


bounds for each estimate represent 90% credible intervals, adjusted from the confidence level assigned by each expert using linear extrapolation (Bedford & Cooke, 2001). For example, if an expert assigned 75% confidence to the interval [35, 60] with a best estimate of 45,the 90% credible interval would be [45 – (45 – 35)/75 × 90), 45 +(60–45)/75 × 90]= [33, 63]. The pooled outcome is the average of the judge- ments of the 12 experts.


Future planning


We held the future planning meeting on 15 August 2022, with six participants (Supplementary Table 4). The expert elicitation results and areas for future development were discussed and a pilot decision-making tool was devel- oped. This tool synthesized the discussion from the expert elicitation process, and its purpose was to provide guid- ance to conservation practitioners in applying the appro- priate method of nest protection.


Results Expert elicitation


Fig. 2 shows the pooled judgements after the second round of assessment for nest success, where success is defined as at least one individual fledging. Equal weighting linear pool- ing of best estimates for the success rate of nests of wild regent honeyeaters under protection were 0.32–0.49.For re- cently released birds the success rate was 0.25–0.40.For the nests of wild birds, the best-performing candidate mea- sures (based on pooled best estimates) for each category of threat were lethal control (of avian predators), cull (of non-threatened mammalian predators), supplementary food resources (to buffer against extreme weather) and noisy miner control (for competition release). The same candidate measures performed best for recent-


ly released birds, except for the threat posed by mammalian predation, for which tree collars were judged to be slightly better than culling or holding non-threatened arboreal mammals. The results in Fig. 2 need to be interpreted in the context of estimated success rates under the base case of no protection. For wild birds the estimate derived from the data is 0.31 (31/100; Heinsohn et al., 2022). For recently released birds the pooled best estimate is 0.22 (22/100). The results also indicate considerable uncertainty in the


payoff of protection. With the exception of noisy miner control, the lower bound estimates of all options imply the possibility of outcomes worse than doing nothing (i.e. lower bounds extend substantially beyond 0.31 and 0.22 for wild and recently released birds, respectively). Similar- ly, uncertainty implies considerable potential for out- comes that are better than expected, especially for holding or culling non-threatened arboreal mammals.


Oryx, 2025, 59(1), 91–100 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324000942


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