Black-chested Sparrow Peucaea humeralis

Very handsome but rather local sparrow endemic to interior southwest Mexico. Found in scrubby woodland and edge of dry tropical foothills and interior valleys. Usually in pairs or small groups, which keep in touch with high, rhythmic twittering choruses. Can be very skulking. Mostly stays low in brush or on the ground, but sings from atop bushes. Plumage distinctive, with black chest, white whisker, and rusty back.