Chestnut-backed Thornbird

The chestnut-backed thornbird is 19 to 21 cm (7.5 to 8.3 in) long and weighs about 33 to 39 g (1.2 to 1.4 oz). It is the longest member of its genus and has the longest bill. The sexes have the same plumage. Adults have a light gray-brown supercilium that extends beyond the eye and spreads, a thin dark brownish "mask", and dull tawny brownish ear coverts. Their crown is dark gray-brown with dull rufous streaks, their upper back grayish brown blending to their chestnut lower back, their rump grayish brown, and their uppertail coverts reddish brown-tinged grayish brown. Their wings are mostly shades of brown with some rufescence and chestnut flight feathers that have fuscous tips. Their tail's central pair of feathers are dull chestnut with browner inner webs and the rest rufous-chestnut with dull brown tips. Their throat and malar area are white, their upper breast tawny brownish with rufous sides and whitish spots that form an irregular band, their lower breast and belly mottled whitish and brownish, and their undertail coverts rufescent brownish with vague mottling. Their iris is gray, their maxilla dark olive-horn to dark horn, their mandible silver-gray to olive-gray, and their legs and feet gray to blue-gray.

The chestnut-backed thornbird is endemic to Peru. It is known only from a few locations in the upper valley of the Marañón River, in the departments of Cajamarca, La Libertad, and possibly Ancash. It inhabits arid montane scrublands, typically those with short Prosopis or Acacia macracantha trees. In elevation it mostly ranges between 1,800 and 3,100 m (5,900 and 10,200 ft) but occasionally occurs as high as 3,400 m (11,200 ft).

The chestnut-backed thornbird's diet has not been studied but appears to be arthropods. It usually forages singly or in pairs, gleaning prey from branches and foliage up to about 4 m (13 ft) above the ground.