CHG_CANON wrote:
Look at replacing the 55-250 with a longer lens more appropriate to wildlife, not replacing the cropped-sensor camera. A lens that reaches at least 400mm will have a more (more significant) impact on your results.
The Sigma 100-400 6.3(?) is stellar in my opinion. With crop factor considered, it's in the neighborhood of 620mm and has shown me tack sharp results.