Brown Tinamou
Crypturellus obsoletus
The brown tinamou is approximately 25 to 30 cm (9.8–11.8 in) in length and it weighs about 350 to 550 g (12–19 oz). Depending on the subspecies involved, the upperparts vary from dark sooty-brown to bright chestnut and the underparts, which usually are paler than the upperparts, vary from chestnut to light ochraceous. The subspecies griseiventris is unique in having pale buff-grey underparts. All subspecies can be separated from the superficially similar little tinamou by the greyish (rather than whitish) throat. Females are typically larger and more rufescent than the males.
ID text from Wikipedia, CC BY-SA 4.0

Undulated Tinamou
Crypturellus undulatus
The undulated tinamou is about 28–30 cm (11.0–11.8 in) in length, and weighs around 300 g (0.66 lb). Depending on subspecies, it is overall brownish tinged grey to various extents, and has a strong, black, barred to faint vermiculated pattern on the back and neck (for example, while C. u. undulatus is relatively rich brown and strongly barred, C. u. yapura is darker, more grey-tinged, and only has faint vermiculations). It has a whitish throat, and the remainders of its underparts are olive-grey to buff with dark vermiculation on its lower flanks and vent.
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: Brown Tinamou and Undulated Tinamou.