Small shy warbler. Dull brown with a paler belly and brow stripe. Like most bush-warblers, difficult to see as it moves through dense foliage. Listen for its sweet song, consisting of a few introductory notes followed by two long whistles: “ti-ti-tchew weeeeee-cheeeeee’. Visually very difficult to separate from Yellowish-bellied Bush Warbler and Brownish-flanked Bush Warbler, and differences are extremely subtle. Himalayan breeders average more greenish on the back than either of the other two species, and have a strong yellow wash on the belly; Brownish-flanked, with which Aberrant overlaps in the eastern Himalayas, is much browner overall. In central China, Aberrant overlaps with Yellowish-bellied, which has a pale gray throat instead of a yellowish-buff one. Aberrant breeds in shrubby edge, bamboo stands, and open bushy areas in montane and hill areas; upper altitudinal limit averages higher than both Yellowish-bellied and Brownish-flanked.