Here some websites where you could find what you need.
I've just used google to find them ("free sounds").
I recommend you do the same next time before ringing the bell on quadropolis :P.

freesound.org (try "bird")
stonewashed.net (click section "animal sounds")
findsounds.com
soundsnap.com (click section "animals")

Good luck!

If you aren't able to find what you need, try sounds for older releases (like "eisenstern" or sounds in maps like "fanatic_caves").

Try to download something like audocity or fruityloops if you want to make a costum sound...

Check the config of the map Fantasy Castle 5 (fc5). I do remember it having bird sounds because of the models also added, so check there.

What would i do if you guys weren´t here ?

Thanks a lot !! i found so much great sounds.
But i found another problem.

How must the cfg be done to get this sound into the map :?

Greetings