A new species of flightless bird has been discovered on a remote island in the northern Philippines, Filipino and British researchers announced Tuesday.

Team member Carmela Espanola spotted unidentified dark brown birds with orange-red bills and legs near a stream on the island in May 2004.

Researchers used her notes, photographs and recordings of the bird's loud, rasping call to determine that the Calayan Rail is new to science.

Calayan Rail (Courtesy Des Allen & BirdLife International)

Conservationists estimate there are probably up to 200 pairs of the birds, known locally as "pidings," in the area. The crow-sized species is likely flightless, according to scientists at the British conservation group BirdLife International.

Human activities pose a risk of extinction for flightless birds with small ranges, said Nigel Collar of the group. The Calayan Rail isn't under immediate threat, but new roads may jeopardize its habitat.

The Calayan Rail resembles the flying Okinawa Rail of Japan's Ryukyu Islands, but it has a different voice and colour. Rails typically have short, brown feathers.

"I felt sure the Babuyan Islands would hold some interesting discoveries, but I didn't expect to find a totally new species!" said Genevieve Broad, a biologist and co-leader of the expedition.

The group proposed naming the species Gallirallus calayanensis after the small island where it is found.

A description of the bird appears in the scientific journal Forktail, published by the Oriental Bird Club.