Yes a curious question and surely has been asked before. Maybe they like their food a little bit aged and nit completely fresh. The idea of signalling has been suggested but who is that addressed to? Presumably their partners but what message does that convey during the day when the birds don’t usually move, that would not be conveyed easier during the night?
By the way Powerful Owl surely will also eat Tawny Frogmouths.
Philip