Black-capped Sparrow
Arremon abeillei
The black-capped sparrow is about 15 cm (5.9 in) long and weighs about 26 g (0.92 oz). The sexes have the same plumage. Adults have a mostly black head with a white throat and a wide white stripe from above the eye down the side of the nape. They often raise their crown feathers in a shaggy crest. Their upperparts and tail are blue-gray. Their wing coverts are blue-gray; some individuals have small pale tips on them that form two wing bars. Their flight feathers are dusky with blue-gray edges. Their throat is white with a black band below it across the upper breast. Voice: The black-capped sparrow's song is described as "a fast tseeét, tsi-tsi-tsi-tsi tseeét and as "a variable high series of thin, buzzy whistles and loose trills, for example: tsew tsew tsi-tetetetete". Its calls are a "very short, high-pitched tsik", a "high-pitched sibilant or lisping descending tseew", and a "high-pitched buzzy bzee". The first two are usually repeated a few times.
ID text from Wikipedia, CC BY-SA 4.0

Olive Finch
Arremon castaneiceps
The olive finch has olive green plumage with a chestnut crown and nape. The face and throat are dark gray, and the wings and tail are darker in color than the rest. The tail is more rounded compared to other Arremon species. A juvenile olive finch presents similarly to adults but with a duller crown, olive throat and face, and uneven plumage coloration. More specific information on the bird's molt and its timing is not available for this species. It has a brown or dark brown iris, black or dark gray bill, and black tarsi and toes. The olive finch has a length of 15.5-16.
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-capped Sparrow and Olive Finch.