Heard at dusk and into the night, the Western Screech-Owl's most distinctive vocalization is its "bouncing ball" song: a series of 5–9 short, whistled hoots, speeding up ping-pong-ball fashion toward the end. The male uses this for territorial and courtship advertising, often calling from a nest tree or a prospective nest site. In duets sung by a mating pair, the female's notes are interspersed with the male's—her voice higher than her mate's, despite her larger size.
To stay in contact, pairs of screech-owls use a short "double trill" call; when agitated, they make a barking sound. Adult females whinny in response to the male's bouncing ball song, and to solicit feeding and copulation.
Western Screech-Owls snap their bills when approached closely by a potential predator such as a crow, squirrel, or human. Nestlings begin doing this when they are about 8 days old.