You can pay more for a body, and you get more—better resolution, more features, more rugged construction. But these budget SLRs are pretty good, and leave you more $$ for decent lenses.
The Rebel XSi
The main thing is, you’re going to need a lens with a lot of "pull." A good example is Sigma’s 150-500mm F5-6.3 APO zoom. Auto-focus, of course, and optical stabilization for low light. That 500mm outer range will really bring wildlife in close. And it’s not a huge lens—ten inches long and about four pounds. At $1,400, it’s not unreasonably priced given all it does. Tokina makes a somewhat lesser 80-400mm F4.5-5.6 lens that sells for about $500 and still offers good versatility.
I wish you could get a decent fixed-focal-length tele, but these days those are pretty exotic items. Canon’s own EF 400mm F5.6 lens ($1,200) is one of the better ones. Match that with a Sigma 70-200mm F2.8 ($2,400) and a Canon 28mm F1.8 wide-angle ($450) and you’ve got just about every combination covered. I really like the 70-200mm despite its steep price because it’s a super-versatile selection of focal lengths, plus very fast.
If you really want just one lens to do as much as possible, Sigma’s 18-300mm F3.5-5.6 zoom ($500 street price) is really pretty remarkable. Not perfect, but with an 18:1 zoom ratio and compact size, it sure covers the bases. Or, Canon’s 70-300mm F4.5/5.6 ($1,250 street price) plus a wide-angle lens would give you better quality with plenty of versatility. That would likely have my vote for most shooting options for lowest cost, without sacrificing much quality.
Lot of choices. Hope this helps!