The R5 is a beautiful camera, but it is very expensive for what it is and I completely agree that R6 is the optimum option for Birds. If you need to crop so far into an image, a longer lens is needed, or to simply be closer.
One thing that many people do not consider with the R5 in particular, is that the processing the RAW files is incredibly power hangry and many users will need to purchase a new computer to work with the files, if their own machine is over a couple of years old. A Canon colleague calls it a £7k camera: 1 camera body, 1 new laptop and a couple of very expensive CFast cards