Guam rails were once so rare that they were thought to be extinct in the wild. Today they are only found on the adjacent islands of Rota and Cocos.
Like the kingfisher’s fate, the Guam rail fell prey to brown tree snakes that arrived via cargo ships. Without defense against this stranger Predator, the railway population plummeted from around 10,000 to only 21 in 1985.
Breeding programs have improved rail numbers, although there is still work to be done.
https://gizmodo.com/animal-species-saved-from-extinction-1850234291 Animal Species Saved From Extinction
