Black-billed Shrike-Tyrant
Agriornis montanus
The black-billed shrike-tyrant is 22 to 24 cm (8.7 to 9.4 in) long. The sexes have the same plumage. Adults of the nominate subspecies A. m. montanus have a whitish stripe above the lores, a buffish white broken supercilium, and brown-streaked white cheeks. Their crown and upperparts are dark grayish brown. Their wings are mostly dark grayish brown with whitish tips and edges on the inner flight feathers. Their underwing coverts are cinnamon-buff to buffy white. Their central pair of tail feathers is blackish; the rest are white with dark bases on their inner webs. Voice: The black-billed shrike-tyrant is not highly vocal but sings more frequently at dawn than during the day. Its voice has been described as "a loud, ringing wheee, wheeeu or just sheeeu." Another description calls its song "a loud, musical, whistled, rising-falling WEEYOO" and its call "a rising wee?".
ID text from Wikipedia, CC BY-SA 4.0
Grey-bellied Shrike-Tyrant
Agriornis micropterus
The grey-bellied shrike-tyrant is 23 to 24.5 cm (9.1 to 9.6 in) long. Adult males of the nominate subspecies have a gray-brown crown, a whitish supercilium, rufous-tinged ear coverts, and black and white streaked cheeks. Their upperparts are gray-brown. Their wings are mostly gray-brown with whitish edges on the secondaries and pale grayish coverts. Their tail is mostly black with narrow white edges on the outer webs of the outer feathers. Voice: The grey-bellied shrike-tyrant is mostly silent. Males chasing another give "high-pitched petulant calls". In the breeding season they make a "high-pitched whistle".
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-billed Shrike-Tyrant and Grey-bellied Shrike-Tyrant.