Just for completeness, I did have a lot of pleasure birding with the RF600 F11 lens for a few years - no zoom, fixed aperture, but it served me well (and much lighter and so easier to aim). The RF200-800 is only better as a matter of degree (a bit more reach, a bit more light, and occasionally that zoom is useful), rather than a step change improvement. That “degree” does of course mean some shots noticeably change from OK to nice, because bird shots are often on the limits of what a camera can make look good.