Nothing wrong with either of those cameras but for nature and extremes sports you need long lenses and fast glass. 300mm and a F2.8 is what you need but your budget isn't enough. I'm a Nikon user, and the lens I use most for wildlife is the 70-200mm F2.8 VR with either a 1.4 or 2x converter to give me a 98-280mm at F4 or 140-400mm F5.6, but the lens alone cost about £1,500.
You could get a Canon EF 200mm f2.8 L USM MKII Lens at about £624 but it doesn't have IS but would allow you to use extenders with it.
Also, check out the second-hand market where you live as you may get a better deal.
