Responses
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falconets, kestrels, merlins, and sparrowhawks are small-ish falcon-like birds
See an american kestrel on a finger: http://kestrelfalconry.com/pics/kestrel_glove.jpg
Also there's also this really adorable bird called a pygmy falcon but that is probably too small to use for falconry/message sending:
https://en.wikipedia.org/wiki/Polihierax
it's really hard to find a species with the right morphology. (dirty white (with brown specks) underbelly+face, dorsal side brown, wings+tail black tipped with possible bands, yellow eyes+beak+legs, larger male with white breast and brown crest)
Had me wondering… are falcons meant to be as small as a finch? She’s super small