What is the name of this bird?

So, a while back I watched a documentary about how a certain blackbird species (that only lived on a certain island) went down to literally only a few in wild population. The birds, the scientists noticed, would lay one egg at a time. When they took the egg (and put it in another bird's nest, who would then take care of the blackbird as if it were their own) the bird would lay another egg. They did this a lot and saved the species. What was the name of the bird species?