The tesias are a genus, Tesia, of Old World warbler. Though once included in the large family Sylviidae, more recent research placed it within a new family, Cettiidae. The four species inhabit undergrowth of montane forests in South and Southeast Asia, where they are resident or short-range migrants. They have longish legs and appear tailless, with (seemingly) only 8 rectrices. Their simple songs are fairly loud, and their nests are typically ball-shaped. Their name is derived from Tisi, the Nepalese name for T. cyaniventer.

(Source: https://en.wikipedia.org/wiki/Tesia)