Barred Forest Falcon
Micrastur ruficollis
The barred forest falcon is 31 to 39 cm (12 to 15 in) long. Males weigh 144 to 184 g (5.1 to 6.5 oz) and females 200 to 322 g (7.1 to 11.4 oz). Adults of most subspecies are typically dark slate gray above; the tail is tipped with white and has three to six narrow white bars. The throat is pale gray, shading to the darker slate of the crown. The rest of the under parts, including the under-wing coverts, are white, finely and clearly barred with black or dark gray. The upper breast is a darker gray. The primary remiges are dark brownish-gray with off-white bars on the inner webs. Subspecies, M. Voice: The barred forest falcon's "advertising call" is "a somewhat dog-like, monotonous yapping, "keyak", "ark" or similar". Another call is a "bouncing-ball series..."cah cah cah-cah-cah", or similar". Neighboring males spar when one gives "a rapid, swelling chitter and the other a rapid clucking".
ID text from Wikipedia, CC BY-SA 4.0

Collared Forest Falcon
Micrastur semitorquatus
The collared forest falcon has a dark coloured back with a white neck and breast. The species has three morphological variants (morphs): pale, tawny and dark. The former two have a light coloured collar at the back of their neck, which explains their name. This is the largest species of the forest falcon genus, with a total length of 46 to 58 cm (18 to 23 in), wingspan of 72 to 86 cm (28 to 34 in) and male weights of 467 to 646 g (1.030 to 1.424 lb), averaging some 523 g (1.153 lb), and female weights of 649–940 g (1.431–2.072 lb), averaging 740 g (1. Voice: The call of the forest falcon has been described as a distinctive low, almost human-like ow or ahr. During the breeding season, these vocalizations can be heard before sunrise every morning and into the mid-morning. The low-frequency of the sound and the timing at which they tend to communicate makes it possible for them to be heard at great distances in the dense forest canopy.
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: Barred Forest Falcon and Collared Forest Falcon.