difference

The difference between birdsong (one word) and whistles is that the sound we call a whistle is a sound made by humans in their mouths, while the sound we call birdsong is made in an organ that only birds have, called the syrinx.

Pankajk--

Welcome to A2K.

The usual terms for birds' calls: "song", "trill", "whistle" and suchlike were probably coined by poets rather than scientists.

Furthermore words that might describe a "chick-a-dee-dee-dee" are conspicuously lacking in describing "kaa kaa kaa".

Your "song" might be another man's "whistle"--or even a "clucking" or a "croak".

Yep. Birds do more than whistle

http://www.youtube.com/watch?v=VjE0Kdfos4Y

Little buggers also do falling trees. Frightene the crap out of you in the bush.