For decades, the research community thought that the small, olive-green songbirds found on two Japanese islands were identical. But a new study has revealed these birds are actually two distinct species, ones that have been evolutionarily isolated for millions of years and are now facing the risk of extinction. Researchers discovered a population of the […]

For decades, the research community thought that the small, olive-green songbirds found on two Japanese islands were identical. But a new study has revealed these birds are actually two distinct species, ones that have been evolutionarily isolated for millions of years and are now facing the risk of extinction. Researchers discovered a population of the newly named Tokara leaf warbler (Phylloscopus tokaraensis) on the remote Tokara archipelago in 1988. Back then, it was considered to be Ijima’s leaf warbler (Phylloscopus ijimae), found in the Izu Islands, some 1,000 kilometers (620 miles) away. An international team of researchers, led by Per Alström from Uppsala University in Sweden and Takema Saitoh of the Yamashina Institute of Ornithology in Japan, has now analyzed the genetic data and songs of the birds on the two islands. Genetic analysis showed that a “deep split” between the two lineages occurred approximately 3.2 million years ago, the authors write. The researchers also found that while the two bird populations are virtually indistinguishable in appearance, their songs say otherwise. In an email to Mongabay, Saitoh said the Tokara species’ songs are lower in pitch and faster in pace than those of its Izu relatives. This acoustic divide is so distinct that the researchers were able to correctly classify 100% of Tokara recordings based solely on their vocal patterns. The recognition of the Tokara and Ijima’s leaf warblers as separate species means they’re even rarer than previously realized. The Tokara leaf warbler is known to breed only on the…This article was originally published on Mongabay

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