Massive declines and local recoveries: First range-wide assessment spotlights ending egg-taking as key to the survival of <i>Macrocephalon maleo</i> (Maleo)

Abstract The communally nesting, Critically Endangered Macrocephalon maleo (Maleo) is an iconic species endemic to Sulawesi, Indonesia, yet despite decades of legal protection its populations have declined sharply across its range. We performed the first-ever range-wide field survey of Maleo nesting grounds, visiting 122 known and identifying 58 previously unrecorded sites, collecting physical and biological data and interviewing local informants at each. We added information from the literature for another 48 abandoned sites, documenting a total of 228 historic and current nesting grounds. We then constructed a profile of historic and current populations and area of occupancy (AOO) units across Sulawesi. Between 1980 and 2019, 55% of active nesting grounds became inactive, and all but one of the 94 sites that remained active hosted fewer birds in 2019. In 2019, 85% of all 228 known nesting grounds were either completely abandoned or just barely active, hosting no more than 2 pairs day–1 at peak season. However, conservation efforts have also produced significant recoveries and discoveries. Our survey increased the range of described landscape types where Maleo nest from 2 to 4, and documented Maleo nesting in previously unrecorded places, including artificially created sandy areas. As the Maleo’s maximum travel distance (MTD) beyond nesting grounds is unknown, we applied a cost-based approach using possible MTDs of 25, 40, and 50 km to define AOO “Units” that represent a set of separate range-wide subpopulations defined by each MTD. Between 1980 and 2019, the overall AOO declined by 37%, 26%, and 19% at MTDs of 25, 40, and 50 km, respectively; the number of active nesting grounds in each isolated Unit declined by 58%, 78%, and 80%, respectively; and fragmentation (i.e., the total number of Units) increased by 5%, 100%, and 125%, respectively. In some areas, Maleo may be changing their behavior in response to egg predation by humans. Ending egg-taking has now clearly been shown to produce Maleo increases in multiple locations and is crucial to range-wide recovery of the species.