The Plain-tailed Wren is a large wren of bamboo thickets in the mountains of northwestern South America. Found from 2200 to 3200 meters in elevation along the Andes, it ranges from southern Colombia to northern Peru. The species shows an olive-rufous back, rufous wings and unbarred rufous tail with buffy-gray underparts and a gray-, black-, and white-striped head and face. It is highly unusual among similar wrens in having an unbarred tail. Plain-tailed Wren shows different plumage on the east and west slopes of the Andes; east-slope birds are mostly unspotted below, while west-slope birds are marked with heavy black spotting on the breast.