Bay-crowned Brushfinch

The bay-crowned brushfinch is 16 to 17 cm (6.3 to 6.7 in) long. The sexes have the same plumage. Adults of the nominate subspecies have a black forehead and a deep rufous crown and nape. Their face is black with a wide white lower cheek and a thin black line below the front of it. Their upperparts are olive-gray; their wings and tail are slightly darker with white on the marginal coverts. Their chin and throat are white with a light gray breastband below them that extends along the flanks and is more olive-gray at the rear. The rest of their breast and their belly are whitish and their crissum buffy. Juveniles have browner upperparts than adults and buffy underparts with faint streaks. Subspecies A. s. simonsi has a rufous forehead, a white spot above the lores, and darker gray upperparts than the nominate. Both subspecies have a dark red-brown iris, a long, thick-based black bill, and grayish legs and feet.

Subspecies A. s. simonsi of the bay-crowned brushfinch is the more northerly of the two. It is found from southern Ecuador's Loja Province south into northern Peru's Tumbes Department. The nominate is found on the Pacific slope of the Andes in Peru from Tumbes south through most of Ancash Department. It inhabits montane scrublands and the undergrowth and edges of montane woodland. In elevation it is found mostly between 1,300 and 2,300 m (4,300 and 7,500 ft) in Ecuador and between 1,150 and 2,800 m (3,800 and 9,200 ft) in Peru.

The bay-crowned brushfinch's diet has not been studied but is known to include insects, seeds, and fruits. It forages on the ground, where it scratches in leaf litter, or slightly above it in vegetation. It typically forages in pairs or small family groups.