I think the Canon 100-400mm would suit your needs. It's a fairly large lens in size, but you don't buy a DSLR to have a compact camera, you want the quality.


On a crop body I think you'd get more benefit from something in the 100-400mm range than one of the 70-200mm's so I think it's a good choice.


I'd stay clear of the Sigma 50-500mm. I've useda friend's(albeit on a sony body) and I wasn't impressed with the quality of images. Build quality is great, images not so great.


Ben.