Sumatran Ground Cuckoo (Carpococcyx viridis)
Scientists have recorded the call of the extremely rare Sumatran Ground Cuckoo. This bird lives in the remote forests of Indonesia, on the island of Sumatra. It was thought extinct for 81 years, until a single bird was spotted in 2002. Up until now, however, noone knew what this bird sounded like. This was a problem, since a birds call is one of the key methods scientists use to find birds, and estimate their population.
The birds call, consisting of two piercing shrieks, was recorded when a trapper handed over the bird to scientists. The bird, whose foot was injured, is being nursed back to health, and will be released back into the wild. So far it is not known if the bird has other vocalizations.
This article has a great picture, as well as a link to a recording of the bird's call.