Frisk’s etymological dictionary concurs with Frank Dauenhauer’s answer, that the bustard was called ōtis ‘one with ears’ (“from its cheek tufts or head? See Thompson, Birds”); thus also ōtos ‘scops owl’, from its ear tufts.
If you go to A glossary of Greek birds : Thompson, D’Arcy Wentworth, 1860-1948 Sir, p. 200, you’ll find he says the etymology is doubtful, as well as whether the bird is the Great bustard (Otis tarda) or the Houbara bustard. But I don’t see what else it would be.
