After noticing a bird known as a brush that lived in the forest singing differently than the same bird that lived in the mountains, a team of scientists identified a new species.

Published in the journal Avian Research, the new study detailed the Zoothera salimalii, or the Himalayan forest thrush. The researchers found the bird to live in northern India and China, but the newly discovered species is just the fourth new one identified in India since 1947.

"There aren't too many new birds to be found in the world," study lead author Per Alström told BBC News. "So it's exciting when you find one.

"He did a lot of work on Indian birds and has been really important for bird conservation and knowledge about birds in India."

The researchers came up with the new species' name to honor Sálim Ali, a renowned Indian ornithologist.

"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," study co-author Pamela Rasmussen, a biologist at Michigan State University, said in a press release.

Before the new species was discovered, the bird was known as the plain-backed thrush. Researchers first noticed a difference between the way two groups' sang during fieldwork in 1999.

"They had - to us - incredibly different songs. We couldn't at first find any differences in plumage or structure between them. But we didn't actually see the forest one very well, because it was extremely elusive - extremely hard to see," Alström said. "They really are very different, even though they look superficially very similar to each other.

"They have had separate evolutionary histories for a very long period of time - possibly the same length of time as humans and chimpanzees have been separate from one another."