The Canon USA is store is having a sale on refurbished copies of the Canon RF 600mm f/11 IS STM & Canon RF 800mm f/11 IS STM. These would be perfect for your wildlife and bird shooting.
We have used both of these lenses, and they’re a revelation, especially for the price. If you can get yourself some distance between your subject and the background, you can get very pleasing out of focus areas. These lenses are small and light for super-telephoto focal lengths.
Canon RF 800mm f/11 IS STM Key Features
First Compact and Lightweight 800mm Super Telephoto RF Lens
Excellent Portability made Easier with an Extending/Retracting Locking Lens Barrel Design
Gapless double-layer Diffractive Optics (DO) reduce Chromatic Aberration for
High Image Quality
High Image Quality at a fixed f/11 Aperture...