An occupancy approach to monitoring regent honeyeaters

Conservation of rare and highly mobile species is frequently limited by a lack of monitoring data. Critically endangered regent honeyeaters (Anthochaera phrygia, population 350–400) pose a substantial conservation challenge because of their high mobility and irregular settlement throughout their estimated 600,000-km² range. Given an ongoing population decline, enhanced monitoring efforts to inform population management are needed. We conducted an occupancy survey of regent honeyeaters and other nectarivores over 880 km² of the species' core range in New South Wales, Australia, during spring 2015. We located approximately 70 regent honeyeaters, potentially representing 20% of the population. Presence of regent honeyeaters was best predicted by high local nectar abundance. Detectability of regent honeyeaters when breeding (0.59) was similar to common, co-occurring nectarivores and was sufficient to distinguish absence from non-detection. For rare and highly mobile species, monitoring approaches that prioritize sampling extent over site visit duration and explicitly accommodate their life-history attributes can provide valuable population data, with subsequent benefits for conservation.