Using decision analysis to develop a framework for nest protection for threatened birds J OY S. TRIP OVICH 1 , 2 ,TERR Y WAL SH E 3 ,ANDREW E L P H I NS T O NE 1


DEAN INGWE RSE N 4 ,MICK RODER I C K 4 and B ENJAMIN J. P ITCHE R * 1 , 5


Abstract The regent honeyeater Anthochaera phrygia is a Critically Endangered Australian songbird, with current population estimates of ,300 individuals remaining in the wild. Low nest success is a factor preventing the recovery of the population, and management remedies are needed. However, a lack of data on intervention success raises uncer- tainty and impedes planning. To identify management pri- orities under uncertainty, we engaged with conservation practitioners and key stakeholders to develop and evaluate potential nest protection interventions. Four categories of threats were considered: avian predators, mammalian pre- dators, extreme weather events and avian competitors. The interventions with the highest predicted probabilities of nest success under each threat categorywere, respectively: lethal control of avian predators, the use of tree collars to control arboreal mammalian predators, the provisioning of supplementary food and nesting resources during extreme weather events, and control of the noisy miner Manorina melanocephala, a competitor species. Our ana- lysis shows that by applying a combination of conservation actions alongside improvements in nest detection, it is possible, based on the opinion of experts, to provide a path- way for the recovery of the regent honeyeater.


Keywords Anthochaera phrygia, Australia, Critically En- dangered, expert elicitation process, nest success, predator control, regent honeyeater, songbird


The supplementary material for this article is available at doi.org/10.1017/S0030605324000942


a transparent and credible framework to improve decisions that are based in part on imperfect knowledge (Yokomizo et al., 2014; Bolam et al., 2019; Hemming et al., 2022). Decision science has increasingly been used in conservation science (Possingham et al., 2001; Conroy & Peterson, 2013). Conservation practitioners are often required to make decisions based on dynamic and complex systems where empirical evidence is lacking or uncertain, or data are in- complete (Martin et al., 2012). Expert judgement has been used in decision-making to inform a range of conservation management issues from assessing the viability of trans- locations (Johnson et al., 2010) to predicting the distribu- tion of a species (Murray et al., 2009) and examining the impacts of climate change on population dynamics of spe- cies (O’Neill et al., 2008). The regent honeyeater Anthochaera phrygia, a Critically Endangered songbird (BirdLife International, 2018) that has ,300 adults remaining in the wild (Heinsohn et al., 2022), is facing a major barrier to recovery with nest success at historical low levels (Crates et al., 2019a). Nests are thought to fail primarily because of predation (Taylor et al., 2018), but other factors could contribute substantially. The season- al breeding rate of regent honeyeaters has declined from c. 1.51 juveniles per female in the 1990sto c. 0.99 juveniles per female in 2015–2017 (Crates et al., 2019b; Heinsohn et al., 2022). Data from the National Regent Honeyeater Monitoring


Introduction


ncertainty in decision-making occurs in a range of dis- ciplines, including public health, finance, economics and conservation management. Decision science provides


U


*Corresponding author, bpitcher@zoo.nsw.gov.au 1Taronga Institute of Science and Learning, Taronga Conservation Society


Australia, Mosman, Australia 2School of Biological, Earth and Environmental Sciences, University of New


South Wales, Sydney, Australia 3School of Ecosystem and Forest Sciences, University of Melbourne, Melbourne,


Australia 4BirdLife Australia, Carlton, Australia 5School of Natural Sciences, Macquarie University, Sydney, Australia


Received 17 January 2024. Revision requested 4 April 2024. Accepted 27 June 2024. First published online 27 December 2024.


Program, the long-term zoo breeding, release and wild population monitoring programme that commenced in the 1990s, were recently synthesized in a population viability analysis (Heinsohn et al., 2022). This reported that a recruit- ment rate of 1.5–2.0 juveniles per female per season is needed to arrest population decline (Heinsohn et al., 2022). This analysis shows that, coupled with habitat pro- tection/restoration and the reintroduction of zoo-bred birds, boosting the success rate of nests in the wild will be a crucial part of saving regent honeyeaters from extinction over the next decade. Nest success is highly variable between years and at dif-


ferent sites, and it can vary depending on the position of the nest within the tree crown. Moreover, there is no clear understanding of patterns or trends of the success or fail- ure of these nests. There are also inconsistencies in what is considered a breeding nest versus an ancillary nest (i.e. birds of some species will build multiple nests within a breeding season that are not used for egg-laying; Mac- queen & Ruxton, 2023), and this needs further clarification.


This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial licence (http://creativecommons.org/licenses/by-nc/4.0), which permits non- commercial re-use, distribution, and reproduction in any medium, provided the original article is properly cited. The written permission of Cambridge University Press must be obtained prior to any commercial use. 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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