How do the chicks of birds that use other birds to raise their young, such as cuckoos and koels know that they are cuckoos or koels and not the other type of bird?

How do the chicks of birds that use other birds to raise their young, such as cuckoos and koels know that they are cuckoos or koels and not the other type of bird? – Linsay An interesting question posed on the ABC Science Website http://www.abc.net.au/science/articles/2013/09/09/3788492.htm Cheers, John =============================== To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) to: birding-aus-request@vicnet.net.au http://birding-aus.org ===============================