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The large-billed reed warbler is one of the world's rarest birds. ((Wildlife Conservation Society/Associated Press))

The first known breeding area of one of the world's rarest birds has been found in the remote and rugged Pamir Mountains in war-torn Afghanistan, a New York-based conservation group said Monday.

A researcher with the Wildlife Conservation Society stumbled upon the small, olive-brown large-billed reed warbler in 2008 and taped its distinctive song — a recording experts now say is probably the first ever. He and colleagues later caught and released 20 of the birds, the largest number ever recorded, the group says.

At the time, however, Robert Timmins, who was conducting a survey of avian communities along the Wakhan and Pamir rivers, thought he was observing a more common warbler species.

But after a visit to a Natural History Museum in Tring, England, to examine bird skins, Timmins realized he had something else on his hands.

Lars Svensson, a Swedish expert on the family of reed warblers and familiar with their songs, was the first to suggest that Timmins's tape was likely the first recording of the large-billed reed warbler.

"Practically nothing is known about this species, so this discovery of the breeding area represents a flood of new information on the large-billed reed warbler," said Colin Poole, executive director of group's Asia Program. "This new knowledge of the bird also indicates that the Wakhan Corridor still holds biological secrets and is critically important for future conservation efforts in Afghanistan."

Researchers returned to the site of Timmins's first survey in 2009, armed with mist nets used to catch birds for examination. The research team broadcast the recording of the song, which brought in large-billed reed warblers from all directions, allowing the team to catch 20 of them for examination and to collect feathers for DNA.

DNA confirms discovery

Lab work comparing museum specimens with measurements, field images, and DNA confirmed the find: the first-known breeding population of large-billed reed warblers.

"This is great news from a little-known species from a remote part of the world and suggests that there may be more discoveries to be made here," said Mike Evans, an expert on birds in the region for Birdlife International. He did not take part in the discovery.

Researchers are hoping the discovery sheds light on the bird, which U.K.-based Birdlife International in 2007 called one of the world's rarest. The first specimen was discovered in India in 1867, with more than a century elapsing before a single bird was found in Thailand in 2006.

But the announcement of the discovery of a home to the large-billed reed warbler came the same day Taliban militants launched an assault in the Afghan capital of Kabul, underscoring the challenges of doing conservation work in the country.

The bird was discovered in the Pamir Mountains, a sparsely populated region near China that has been relatively peaceful. It is, however, difficult to access — part of the reason the breeding site is only now being discovered.

WCS is the only conservation group doing scientific studies in Afghanistan. It has been involved in helping set up the first national park, Band-e-Amir, in central Afghanistan as well as working with the government to create the first-ever list of protected species.

A preliminary paper on the finding appears in the most recent edition of BirdingASIA, the magazine of the Oriental Bird Club.