For long range wildlife shots I use a Canon EF 100-400mm f/4.5-5.6 L IS USM zoom.

This is an excellent lense which, with the proper technique applied, can produce some good shots hand-held. On a tripod it is truly worth the Canon "L" designation and is capable of capturing sharp detail.

The lense has a push/pull zoom mechanism which takes a little getting used to at first but I have not found it too difficult although I tend to use the lense at 400mm most of the time.