Degree of egg-taking by humans determines the fate of maleo (Macrocephalon maleo) nesting grounds across Sulawesi

The maleo (Macrocephalon maleo) of Sulawesi, Indonesia, is culturally iconic and Critically Endangered, but the causes of its decline have never been systematically analyzed nor its nesting grounds comprehensively surveyed. We visited 122 previously known and 58 previously unrecorded sites, collecting data and interviewing local people at each site. We used ordinal logistic regression to fit models with combinations of 18 different predation, habitat, and nesting ground variables to determine the strongest predictors of nesting ground success, as represented by maleo numbers. At least 56% of known nesting grounds are now inactive (abandoned), and 63% of remaining active sites host ≤ 2 pairs/day at peak season. Egg-taking by humans is the single biggest driver of maleo decline. Protecting eggs in situ predicts higher maleo numbers than protecting eggs through hatchery methods. After egg-taking, quality (not length) of the travel corridor connecting nesting ground to primary forest best predicts nesting ground success. Being inside a federally protected area is not a primary driver of success, and does not ensure persistence: 28% of federally protected nesting grounds have become inactive. Local conservation efforts protected nesting grounds 2‒3 times better than federal protection. We update the methodology for assessing nesting ground status, and recommend five measures for maleo conservation, the foremost being to protect nesting grounds from egg-taking by humans at all remaining active sites.