Less that they “have an open relationship” and more that the birds sneak around behind each-other’s backs. Males go off and try to sneakily impregnate other females, females sneak around and try to get impregnated by other males. You find it in apes too.
Less that they “have an open relationship” and more that the birds sneak around behind each-other’s backs. Males go off and try to sneakily impregnate other females, females sneak around and try to get impregnated by other males. You find it in apes too.