If you are raised by other species, then how do you know who you are? Although heterospecific foster parents rear brood parasitic brown-headed cowbird chicks, juvenile cowbirds readily recognize and affiliate with other cowbirds. That’s because they have a secret handshake or password. Specifically, the “password” hypothesis helps explain this paradox of species recognition: Social recognition processes in brood parasites are initiated by exposure to a password: in the case of cowbirds, a specific chatter call.