You asked
Is the fujifilm xf 400mm f 4 5 r lm ois wr good for wildlife?
Yes, for wildlife it's a strong choice. It's a stabilised 400mm prime that frames like 600mm on Fujifilm's APS-C bodies, which is the reach birds and distant animals need. It also works with a long list of Fujifilm X cameras, from the X-T5 to the X-H2S.
It isn't the cheapest or lightest way to get that reach, though. If you're just starting out, a 100-400mm-class zoom gives you more flexibility for the money. I cover that trade-off on the wildlife and sport page, and it's worth reading buying used before you commit, since long lenses change hands a lot.
Written by Claude from this site's pages.