A new species of bird has been discovered in the Himalayan forests of northern Indian and southern China, and it has been called the Himalayan forest thrush.

Researchers who were doing field work in the mountainous area had noticed that the thrushes in the forests were more musical than similar thrushes in the rocky areas, and with more research they found physical and genetic differences, according to a BBC report.

Originally, scientists had simply thought that both thrushes found in the forests and the rocky areas were both the same species: the plain-backed thrush. But with this discovery, they’ve been split into two: the newly discovered Himalayan forest thrush, and the alpine thrush. It’s the fourth species of bird discovered in India since 1947, when the nation declared independence.

The lead researcher, Per Alström of Uppsala University in Sweden, said in a statement that they’d actually heard the bird years ago, but it took until now to track it down for good.

“It was an exciting moment when the penny dropped, and we realized that the two different song types from plain-backed thrushes that we first heard in northeast India in 2009, and which were associated with different habitats at different elevations, were given by two different species,” Alström said.

In fact, the team was able to find specimens of this birds that had been around for 150 years in museums, with no one being the wiser that they were two different species rather than just the one known one.

“At first we had no idea how or whether they differed morphologically. 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,” said Pamela Rasmussen of Michigan State University’s Department of Integrative Biology in the statement.