...and the Tamron lens is a bit of a dog, adequate for most things but not brilliant.
If you want to spend on long focal length lenses, carry on, in wildlife photography long focal lengths are an asset however your main purchase should be a tripod or at very least a monopod, as others have said. Going down the long focal lengths make sure you buy a lens with a collar that you can attach the tripod to rather than the body of the camera, I would always do this shooting wildlife. A good monopod is a little more portable than a tripod but it comes down to personal choice.
Good long lenses, there's dozens of choices there for Canon cameras, this is pretty good and fairly good value
http://www.sigma-imag...elezoom/150-500mm.htm
I use one of these when I don't have scope to use my fixed Canon Lenses ie
http://www.canon.co.u..._500mm_f4L_IS_II_USM/
Teleconverters are good at extending focal length but buy Canon originals the others just don't work as well.