About Atlapetes crassus Bangs, 1908
Adults of this species weigh 29.5 to 40 g (1.04 to 1.41 oz) and measure 16 to 18 cm (6.3 to 7.1 in) in length. Adult upperparts range from olive to black, while underparts are yellow with an olive tint on the flanks. The sides of the head are black, with a yellow stripe along the crown and a yellow throat. Juveniles have dark brown upperparts, lighter brown underparts, and a rufous crown. This species, the Choco brushfinch, is a permanent resident found in the western Andes of Colombia and western Ecuador. It lives in open cloud forest, the undergrowth of humid forest openings, humid forest edges, and secondary woodland. It occurs mostly at elevations between 600 and 2,300 m (2,000 to 7,500 ft), though there are isolated records from elevations outside this range. Very little is known about the Choco brushfinch's diet. Unlike many other brushfinches that forage mainly close to the ground, this species is known to forage up to 10 m (33 ft) above the ground. It forages alone, in pairs, or as part of a mixed-species foraging flock. Little is also known about this species' nesting timing and behavior. Observers have recorded nest-building activity in Colombia during November, February, and May; eggs have been found in April, and fledglings have been observed in June and July. One recorded nest was a thick cup positioned near the ground, and it held one white egg marked with dusky spots.
