A bird that was long thought to have gone extinct has been rediscovered in Myanmar after a team of scientists used a recording of the species' distinctive call to track it down.

The Jerdon's Babbler (chrysomma altirostre altirostre) -- a small brown bird similar in size to a house sparrow -- was last spotted in Myanmar in 1941 and was thought to have died out altogether.

But a team of scientists in May 2014 managed to uncover multiple birds nesting in a small area of grassland in Myanmar's central Bago region, according to their report published in the latest edition of Birding Asia.

The scientists targeted some of the few remaining patches of wild grassland left along Myanmar's mighty Irrawaddy river, now one of the most heavily cultivated and densely populated regions of the impoverished but emerging southeast Asian nation.

At one small patch of grassland near an abandoned agricultural station, the team heard what they thought could be the babbler's call. They then used a recording of a Jerdon's Babbler from the Indian subcontinent to see if the bird would show itself.

Frank Rheindt, from the National University of Singapore, told AFP he was the first person to spot the bird during the survey, which was also carried out with members of the Wildlife Conservation Society and Myanmar's Nature and Wildlife Conservation Division.

"It was unbelievable," he recalled.

"We played the sound recordings and one of the birds came up from the reed beds. Like many song birds in reed beds you hardly ever see them, they only come out to defend their territory when they hear a territorial call."

Further searches over the next two days uncovered more birds allowing researchers to obtain blood samples and photographs.

- Still at risk -

But researchers warned that the bird's survival is still far from guaranteed given pressure on Myanmar's few remaining grasslands.

"This discovery not only proves that the species still exists in Myanmar but that the habitat can still be found as well," Colin Poole, director of Wildlife Conservation Society's regional hub in Singapore, said in a statement.

"Future work is needed to identify remaining pockets of natural grassland and develop systems for local communities to conserve and benefit from them," he added.

Rheindt said the area of grassland where the bird was found was very small, "around 50-80 hectares" and that new chicken and fish farms were being built nearby.

He added that its plumage and song were significantly different to how it had been described by ornithologists in the early twentieth century -- leading the team to suspect that it may differ from threatened populations found in Nepal, India and Pakistan.

His team now hope to conduct DNA tests to decide if it is a separate species.

Myanmar's quasi-civilian government replaced decades of brutal military rule in 2011. It has since embarked on a series of political reforms and shown itself to be far more open to foreign businesses and academic researchers than the country's generals were.

Myanmar has more species of bird than any other country in mainland Southeast Asia, with ornithologists saying this number is could increase if more scientific research is conducted.