Rat and invasive birds control to save the Tahiti monarch (Pomarea nigra), a critically endangered island bird

Abstract The Tahiti monarch is a critically endangered bird species endemic to the island of Tahiti. In 1998, when a conservation program started, its range was restricted to four valleys, with 19 birds living in accessible lower valleys. In one of these valleys, a remote population located upstream of a series of waterfalls was present but, was first protected only in 2009. The first conservation actions focused on rat control alone and this probably save the species from imminent extinction. However, the accessible population, living in the lower sites, had only increased to 22 birds by 2012 (1 % per annum), part of a global population of just 40 birds. The introduced common myna and red-vented bulbul were identified as additional threats to monarch breeding success. With the help of a network of local inhabitants living near the valley entrance, 8475 mynas and 17859 bulbuls were eliminated in seven years. This study shows that the overall nest and fledging survival was increased by bird control, reduced by heavy rain but not substantially changed by increases in the level of rat control. During this period, the total Tahiti monarch population increased from 40 adults to 79 in 2018, (12 % per annum). Our results illustrate the necessity to control several threats together in order to recover island birds with low productivity. Conservationists need to consider that several other island birds, with low productivity, may need multi invasive control to recover.