[Photo] This rare Sumatran ground-cuckoo was captured in a hunter’s trap (Image: WCS Indonesia).

The song of an extremely rare species of cuckoo has been recorded for the first time. It is only the third confirmed sighting in a decade of the Sumatran ground-cuckoo and knowing its song will help gather more information about the mysterious bird’s distribution, conservationists say. Click here to listen to the recording of the Sumatran ground-cuckoo's call.

Sumatran ground-cuckoos are large birds ??? about 50 centimetres long ??? with green and black feathers. They have so far only been seen on the Indonesian island of Sumatra. According to BirdLife International, the bird disappeared entirely between 1961 and 1997, when one was briefly seen. In 2006, another bird was captured on video in the Sumatran forest by a camera with built-in motion sensors.

"Some species are very cryptic, very good at concealing themselves," says Adrian Long of BirdLife International.

The Wildlife Conservation Society (WCS) suspected that Sumatran hunters were occasionally catching some of the rare cuckoos in their traps, which they use to capture pheasants and small ground mammals. They began working with the hunters, telling them about the bird and asking to be kept informed if the hunters ever captured one.

Their efforts recently bore fruit, when one of the hunters brought them a cuckoo that had been injured in one of his traps. While they were nursing the rare bird back to health, the researchers were able to record its song for the first time. The bird will be released when well.

Name that tune
The song is essentially a double squawk, although the researchers do not know if the bird has any other songs in its repertoire.

"We were extremely lucky to have recorded the bird’s unique call," says Firdaus Rahman, of WCS’s Indonesia Program. "Our team will use the recording to hopefully locate other Sumatran ground-cuckoos, and to eventually secure their protection."

"With a lot of tropical forest species, you often hear them before you hear them, so knowledge of their song is absolutely critical," Long explains.

Call me back
Over the past decade a similar species, the Bornean ground-cuckoo, has been identified thanks to its call. Very little was known about that bird until researchers were able to get a recording of its song. They then went into the forest and played the song on a speaker, which prompted the cuckoos in the forest to call back, allowing the researchers to map their distribution.

In the same way, the Gurney's pitta ??? a bird found in the tropical forest in Thailand ??? had not been for seen for 50 years before it was rediscovered in the 1980s. Since then, researchers have been mapping its distribution, largely by tracking its song, and the bird has even been found in Myanmar.

"Song is a very efficient way of surveying forest and knowing what key species live there," says Long. He says so little is known about the Sumatran ground-cuckoo that it is difficult to know the status of its population. The World Conservation Union has placed the bird on its Red List of endangered species.