Before a green-rumped parrotlet is even able to chirp and squawk, mom and dad teach it a distinct series of sounds used by parrots to recognize a specific individual. In short, they give their nestling a name. To find out how this worked, Cornell University ornithologist Karl Berg and his team swapped eggs between nests in a wild parrotlet population they’ve studied since 1987. Half the parrotlet pairs raised foster chicks, who used the contact calls demonstrated by their adoptive parents. If the calls were genetically predetermined, they’d have used their biological parents’ calls. Host Jenny Nelson talks with Karl Berg about his research, how they manage to listen to the birds in their nests, and why these parrots might have evolved this ability.