New Himalayan bird species found by listening to its unique voice

Himalayan Forest Thrush: Scientists first discovered a new species of bird in northeastern India not by DNA analysis or physical differences, but by their prettier songs. 

An international team of scientists has discovered a new species of bird by studying the musicality of its song. 

“There aren’t too many new birds to be found in the world,” lead author Per Alstrom told the BBC. “So it’s exciting when you find a new one.” 

In a study published in the current issue of Avian Research journal, a team of scientists from Sweden, China, the US, India and Russia explain how they discovered the Himalayan forest thrush Zoothera salimali species, named after the Indian ornithologist Salim Ali. 

Researchers have been analyzing the discovery since 2009, when they suspected the plain-backed thrush Zoothera mollissima, a small bird that lives in northeastern India, was actually two different species. 

“What first caught scientists’ attention was the plain-backed thrush in the coniferous and mixed forest had a rather musical song, whereas individuals found in the same area – on bare rocky ground above the treeline – had a much harsher, scratchier, unmusical song,” explain the authors in a press release. 

Scientists studied the song recordings of each bird, analyzing duration, mean frequency and frequency bandwidth. 

“The song of the Himalayan Forest Thrush sounds much more musical and ‘thrush-like’ than that of the Alpine Thrush,” the scientists write in their paper. “It is built up of a mix of rich, drawn-out clear notes and shorter, thinner ones, with hardly any harsh scratchy notes.” 

And “although their songs are fairly similar, they are audibly different,” say scientists, adding to evidence that they are different species.

The scientists also studied the two species’ morphology and DNA sequencing – but that was only to confirm what the birds’ songs first revealed. 

“The had – to us – incredibly different songs. We couldn’t at first find any differences in plumage or structure between them,” Alstrom tells the BBC. 

In fact, the researchers studied museum specimens of the presumed single species for years, trying to recognize physical differences. 

“At first we had no idea how or whether they differed morphologically,” Pamela Rasmussen, from Michigan State University’s Department of Integrative Biology and author of the study, said in a press release. “We were stunned to find that specimens in museums for over 150 years from the same parts of the Himalayas could readily be divided into two groups based on measurements and plumage.” 

The scientists suspect that the Himalayan forest thrush and Alpine thrush began as one species and then evolved into two distinct populations to cope with their very different habitats. The Himalayan forest thrush has shorter legs and a shorter tail, “which I’m sure are adaptations to its habitat. Because longer legs are more useful in open habitats than in forest,” says Alstrom.

Alstrom also discovered a sub-species of India’s new Himalayan forest thrush that lived in China, and named it the Sichuan forest thrush. DNA analysis suggests that these three species – although recently discovered – have actually been genetically different for millions of years.

The Himalayan forest thrush is the fourth new bird species to be discovered in India since the country’s independence in 1947. And since 2000, a global average of only five new species have been discovered each year, the majority in South America.