Japan Gets 1st New Bird Species In 45 Years After Taxonomic Split

TOKYO, April 12 (Bernama-Kyodo) -- A songbird population that breeds on remote islands in southwestern Japan has been recognised as genetically distinct, giving the country its first new bird species in 45 years, Kyodo News reported.

The newly named Tokara leaf warbler, from the Tokara Islands of Kagoshima Prefecture, had long been considered the same species as the Ijima's leaf warbler found more than 1,000 kilometres away in the Tokyo-administered Izu Islands.

The two populations, which are summer visitors, are nearly indistinguishable to the naked eye, both showing an olive-green back, a grey head, whitish underparts and a pale orange lower bill.

Doubts over whether the two populations were truly identical, given the vast geographic distance between them, led a multinational team of biologists from institutions in Japan, China and Sweden to investigate the relationship.

According to their research published in the March edition of the international academic journal PNAS Nexus, genetic analysis showed a deep split, with the two lineages estimated to have diverged around 2.8 to 3.2 million years ago.

The biologists also analysed sound recordings and found that while their calls, used for basic communication, were almost the same, their songs, used to attract mates and mark territory, differed significantly.

The Tokara birds deliver faster, lower-pitched, highly repetitive rattling notes made up of simple elements, while the Izu ones produce smoother, more drawn-out and often more complex notes with multiple elements.

Despite appearing the same, Tokara males are slightly smaller on average, with shorter legs and less space between the beak and the back of the head.

The discovery makes it Japan's first new bird species since the Okinawa rail, an almost flightless bird endemic to Okinawa Island that was formally described in 1981.

The Tokara leaf warbler lives on several islands in the Tokara archipelago, where it forages and sings mainly in the forest canopy and nests chiefly in bamboo undergrowth and is believed to winter in the Philippines.

It was first discovered in 1988 on Nakanoshima, the largest of the 12 islands of the archipelago, and the only one where breeding has been confirmed.

Despite being common there, it faces a high risk of extinction due to its small, isolated range, according to the Yamashina Institute for Ornithology, which was involved in the research.

Its habitat on that island has already been damaged by a pine wilt disease outbreak that has reduced forest cover, as well as by feral goats whose grazing has affected undergrowth vegetation.

The discovery of the new cryptic species demonstrates the possibility that hidden biodiversity still exists among Japan's bird species. How to protect them from extinction and conserve them is the challenge," the institute said.

-- BERNAMA-KYODO