Acoustic monitoring and occupancy analysis: cost-effective tools in reintroduction programmes for roroa-great spotted kiwi

Monitoring the response of wildlife populations to conservation management, such as translocations, is crucially important for assessing its effectiveness. Passive acoustic monitoring (PAM) is an emerging tool for monitoring cryptic and elusive species and is increasingly used in the management of kiwi. Inferences from data collected by PAM can be largely improved by occupancy analysis. By modelling occupancy, we overcome the issue of incomplete detectability, which would otherwise lead to underestimating actual site occupancy. Here we demonstrate the utility of occupancy analysis in a reintroduction programme for roroa-great spotted kiwi (Apteryx maxima, formerly known as A. haastii) in the Nina Valley, Lake Sumner Forest Park. We analysed PAM data from two survey years, 2012–2013 and 2017–2018 from the Nina Valley and the Hawdon Valley, Arthur's Pass National Park, which was the source population of the translocated birds. Occupancy estimates increased significantly between the two survey years at both study areas, despite the translocation of approximately 20% of known territorial adults (four pairs) from the Hawdon Valley to the Nina Valley in 2015. Moreover, at least three out of four territories, where adult birds were removed, were re-occupied by new pairs within three years. Site occupancy increased in the Nina Valley from 0.20 (SE 0.10) to 0.72 (0.10), and in the Hawdon Valley from 0.63 (0.10) to 0.95 (0.04). Detectability varied significantly between study areas and was influenced by the length of survey night, breeding/non-breeding season, and also wind speed. The differences between the naïve and estimated occupancy values underscore the benefits of occupancy modelling for measuring population response to conservation management. This study highlights the utility of using PAM in monitoring translocation outcomes: to track changes in occupancy and local distribution, as well as assessing impacts on the source population following the birds' removal for translocation.