Forgot to mention. The babies have to repeat back the incubation call, its at such a pitch (and i believe she tells it right when she lays it, to.) that the cowbird just cant imitate it.I know! I love fairy wrens because you know cow birds? They sneak eggs into other birds nest so they take care of them. (pushing the other birds actual young out due to the size)
anyway, fairy wren has a passcode for them, while their in a egg. called a incubation call, later when the mom is bringing food, or in the dark. She can tell who is, and who is not her baby. And who to feed.
isnt that just amazing?