Guam rails were once so rare that they were presumed extinct in the wild. Today, they’re only found on the adjacent islands of Rota and Cocos.
Like the fate that befell the kingfisher, the Guam rail fell prey to brown tree snakes, which arrived via cargo ships. With no defenses to this foreign predator, the rail population plummeted from around 10,000 to just 21 in 1985.
Breeding programs have improved the rails’ numbers, though there’s still plenty of ground to cover.
Source : https://gizmodo.com/animal-species-saved-from-extinction-1850234291