You might want to read this:


http://www.the-digital-picture.com/Canon-Lenses/Canon-Wildlife-Lens.aspx





I've got the 70-200 f4L myself, but for wildlife I wouldn't recommend it. For larger animals the 200mm might do the trick if you get close, but for birds you must be very very close to get a nice shot.


The 70-200 f2.8L lens is a very nice zoom-lens though. Also comes in handy for a lot more than just wildlife. I must say that the Image Stabilized version is certainly a major plus.


You might also want to look into the Post your best nature picture and post your best birds picture on this forum and look at the lenses they use for the pictures:


http://community.the-digital-picture.com/forums/t/850.aspx


http://community.the-digital-picture.com/forums/t/2706.aspx


That must give you a good insight of what you want and what to expect.


good luck