Chaco Sparrow Rhynchospiza strigiceps

Small sparrow found in lowlands and foothills from northern Argentina to southeastern Bolivia. It has chestnut and gray stripes on the head and faint black and white mustache streaks. Similar to Yungas Sparrow, with which it was formerly lumped as Stripe-capped Sparrow, but is smaller with less black between the eye and bill, browner wings, and different voice. Inhabits open, grassy habitats with scattered trees and low scrub. Song is a fairly rapid series of sweet whistles, repeated every few seconds.