Black-crowned Antshrike
Thamnophilus atrinucha
The black-crowned antshrike is 14 to 15 cm (5.5 to 5.9 in) long and weighs 20 to 28.5 g (0.71 to 1.0 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 significant sexual dimorphism. Adult males of the nominate subspecies have slaty gray upperparts with a gray forehead, a black crown and nape, a hidden white patch between their scapulars, and white-tipped black uppertail coverts. Their face is grizzled gray. Voice: The black-crowned antshrike's most common song is "a series of uh notes ending with a single erk at a higher pitch". Both sexes sing, commonly in the morning but at any time of day. The song has been written as "wur wur wur-wur-wur-wur'wur'wur'wur; AH" and "anhanhanhanhanhanhanhanhanhánh". Its calls include "a 1–4-note (usually 2) caw arr-arr and a bark-rattle: arr-grr'r'r'r".
ID text from Wikipedia, CC BY-SA 4.0

Variable Antshrike
Thamnophilus caerulescens
The variable antshrike, as its common name suggests, is arguably the species of antbird with the most variable plumage. It is 14 to 16 cm (5.5 to 6.3 in) long and weighs 15 to 24 g (0.53 to 0.85 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 significant sexual dimorphism as well as the differences among subspecies. Adult males of the nominate subspecies T. c. caerulescens have a black crown and nape and a gray face. Voice: The variable antshrike's song varies somewhat with geography but the differences are clinal. In general its song is "a simple countable series of usually 6–7 plaintive, evenly spaced whistles of same pitch and intensity". Variations include the pitch and intensity of the first and last notes and the song's pace. The song has been written as "nyah nyah nyah nyah" and "au-au-au-au".
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Black-crowned Antshrike and Variable Antshrike.