A rare bird known to reside up in the mountains of central China has been singled out as a completely new species because of its unique song. It is not linked to any other bird.

The Sichuan Bush Warbler, which hides away in the vegetation, has rarely been studied. However research published Friday in Avian Research has confirmed that it stands separate from other types of bird.

But the “exceedingly secretive” Sichuan Bush Warbler sounds quite different from its neighbor, a Michigan State University biologist who co-authored the paper said in a statement. “Its distinctive song … consists of a low-pitched drawn-out buzz, followed by a shorter click, repeated in series,” Pamela Rasmussen said.

You can listen to that song here, via the Avian Vocalizations Center.

Although exceedingly hard to spot, the new species appears to be pretty common in the region, Rasmussen noted.

The birds are visually distinguished by only slight observable differences, based on the specimens studied by researchers. The Sichuan Bush Warbler is “typically greyer (less russet) above and on the breast-sides and flanks,” the paper explains. But, the researchers note, “this difference does not always hold.”

All of the specimens that researchers were able to examine turned out to be males, so it’s possible that a female Sichuan Bush Warbler could be more visually distinct.

The Russet Bush Warblers and the Sichuan Bush Warblers seem to be accustomed to living in close quarters. Two males, one of each species, that were observed by researchers “held territories that were adjacent, and probably at least partly overlapping,” the paper explains, adding:

Most of the time, the two birds were singing from different sides of a road, at close distance from each other, although the [Russet Bush Warbler] male was also heard on two occasions singing within what was undoubtedly the Sichuan Bush Warbler’s territory. The Sichuan Bush Warbler was seen chasing the [Russet Bush Warbler] male across the road once.

The researchers didn’t seem too surprised to find a new species of bird among the warblers, the paper indicates. The Russet Bush Warbler in particular has a “long history of taxonomic confusion.”