Grey-sided Bush Warbler Cettia brunnifrons has a remarkable song and a striking head pattern, making it one of the easier Cettia to identify. Each of the three ssp. occupies a disjunct range in the Himalayas and on the eastern Tibetan Plateau, with umbratica in southeastern Tibet and western Yunnan north through western Sichuan to southern Gansu. Breeds to 4000 m in scrub and grass both above and below the tree line. Descends in winter to 500 m. Shares chestnut-brown cap with larger chestnut-crowned bush warbler, but head of the grey-sided is slightly more contrasting; supercilium is better defined and whiter in front of eye (but shorter behind), and blackish-brown eye-stripe is more distinct. Rest of upperparts drab rufous-brown. Underparts also distinguish grey-sided from chestnut-crowned, being greyish-white in center with upper flanks washed ash-grey and lower flanks brownish-grey; undertail coverts brown-buff. Japanese bush warbler is larger with buffish flanks. Juvenile darker than adult, with brownish-olive underparts, and lacks chestnut cap. Juvenile chestnut-crowned has more contrasting whitish throat and belly. Upper mandible grey, lower mandible grey with yellow base. Feet dull brownish-pink. Distinct, two-part song, the first a short, cheerful warble, similar to chestnut-crowned but shorter and faster, the second a squeaky “wheezuu-wheezuu” sounding like the air being squeezed out of a child’s rubber ducky. Sharp call “pseep” has more r-sound than chestnut-crowned, something inbetween a bunting and olive-backed pipit. — Craig Brelsford
ACKNOWLEDGEMENTS
Daniel Bengtsson served as chief ornithological consultant for Craig Brelsford’s Photographic Field Guide to the Birds of China, from which this species description is drawn.
