Castelnau's Antshrike

Castelnau's antshrike is 16 to 18 cm (6.3 to 7.1 in) long and weighs 30 to 35 g (1.1 to 1.2 oz). Members of genus Thamnophilus are largish members of the antbird family; all have stout bills with a hook like those of true shrikes. This species exhibits slight sexual dimorphism. Adult males are mostly black. They have a mostly hidden white patch between their scapulars, white tips on the scapulars, white tips and edges on their wing coverts, sometimes very small white tips on their flight feathers, and white underwing coverts. Their flanks and belly are dark gray. Voice: The song of Castelnau's antshrike has been described as "a short, fast, accelerating 'keoh, keoh, kuh-kuh-kuhkuhkuhkuhkuh' with nasal, bouncing-ball quality" and as "an accelerating, descending series of downslurred notes: kyuk kyuk-kyew-kew-kew'ku'ku'kukuku". Its calls include "a drawn-out 'kawh' " that is sometimes doubled or in a series and "a 'kowah, kr-r-r-' ".