About Mimus saturninus (Lichtenstein, 1823)
The chalk-browed mockingbird, Mimus saturninus, measures 23.5 to 26 cm (9.3 to 10.2 in) in length and weighs 55 to 73 g (1.9 to 2.6 oz). Males are slightly larger than females. For adults of the nominate subspecies, the crown is dark brown, there is a broad white supercilium, a blackish line running through the eye, and white cheeks. Their upperparts are brownish with some darker streaks, and the rump is buffier. Their wings are blackish, and display two obscure bars when folded. Their tail is also blackish; most tail feathers have white tips, and the outermost feathers have white edges. The bird's underside is white from the throat to the vent, though the breast has a gray tinge, and the flanks are buffy with faint dark streaks. Juvenile chalk-browed mockingbirds are browner than adults, have buffier underparts, and show dark streaks on the breast. The subspecies M. s. frater is overall browner than the nominate subspecies, including its rump which is not buffy like the nominate's rump. Subspecies M. s. arenaceus is essentially identical to M. s. frater, but has a larger bill. Subspecies M. s. modulator has some blackish brown spotting on its crown and back, lacks the gray tinge on the breast, and has paler flanks that are often unstreaked. Four subspecies of chalk-browed mockingbird have distinct distribution ranges. The nominate subspecies occurs in southern Suriname and the adjacent Pará state in Brazil. M. s. arenaceus is found in eastern Brazil, from Paraíba state south to eastern Bahia state. M. s. frater inhabits central and eastern Bolivia and most of central Brazil. M. s. modulator ranges from southeastern Bolivia and Paraguay into central Argentina and extreme southeastern Brazil. The chalk-browed mockingbird lives in open areas, including savannas, forest edges, open woodland, pastures with scattered trees, and urban and suburban gardens. It is generally a lowland species, but can be found up to approximately 2,500 m (8,200 ft) in elevation in northern Argentina.
