Controlling trapping, overgrazing and invasive vegetation is key to saving Java's last population of the Black-winged Myna

ABSTRACT The Black-winged Myna (Acridotheres melanopterus) is an Endangered passerine endemic to the islands of Java and Bali, Indonesia. Illegal trapping to supply the cage-bird trade has led to its near-total extinction, with the global population estimated to number fewer than 100 individuals. We estimated the current range and population size of the species at Baluran National Park, which supports Java's last known population, and used species distribution modeling to evaluate potential suitability of currently unoccupied areas across the park to identify priorities for management intervention. We estimate that the Black-winged Myna population numbers 179 individuals (95% CI: 111–288; density: 14.3 ± 3.5 individuals km–2) and that its current range is 12.3 km2. Our model indicated that some 72 km2 of the park (30% of total area) has potentially suitable habitat for the species, and we infer that the principal cause for the disparity between its current and potential range is trapping, compounded by savanna loss and degradation due to illegal domestic cattle grazing and the spread of invasive thorny acacia (Vachellia nilotica). The partial clearance of acacia in recent years appears to have assisted a modest population recovery by the myna. Its further population growth and range expansion in Baluran will depend on effective management of illegal poaching, further clearance of acacia, and easing domestic cattle grazing pressure on areas of savanna, particularly through engagement with communities living inside the park. Any actions that increase the size of the Black-winged Myna population are likely to benefit other threatened savanna-dependent wildlife in the park, notably banteng (Bos javanicus) and Green Peafowl (Pavo muticus). While our models and recommendations may be applicable to other protected areas in Java, and indeed other threatened myna species, trapping and habitat change may have site-specific dimensions, especially outside of protected areas, and thus demand local bespoke solutions. LAY SUMMARY The Black-winged Myna, confined to Java and Bali in Indonesia, is threatened with extinction due to illegal trapping for the cage-bird trade. Baluran National Park supports the last known population on Java. We estimated the number of mynas in the park, mapped where they occur, and assessed their habitat to determine how much of it is currently unoccupied. There are ∼180 Black-winged Mynas in the park, indicating recent population growth. However, they occupy <20% of the potentially suitable habitat, restricting further population growth. Trapping is the foremost factor holding back the mynas, but overgrazing by domestic livestock and invasion by thorny acacia negatively affect the potentially suitable habitat. Thorny acacia eradication must continue. Working with the human communities living in the park is key to alleviating the grazing pressure and addressing the trapping issue.