So, I spent a lot of time looking at the Nikon Z 7ii mirrorless and D850 DSLR. The consensus from multiple sources was that for something like catching a bird in flight (BiF), which is definitely something I intend to do, the D850, a platform from 2017, would do a better job than the Z 7ii, in terms of auto focus (AF). Nikon is already discontinuing lenses for the D850, so it being an old platform is starting to look problematic, and the Z 7ii being not as good with AF for BiF as a 5 year old platform kind of removes it from consideration.
In my attempts to research the AF on those two, I happened across information on the Canon R5 (plain, not "C"inema) and it looks like the AF for things like BiF might be about the best there is, without going to bodies with nosebleed, i.e., $5k for just the body, prices.
Any thoughts appreciated.