Other lenses depends on how well it does, i bought it for a general walk or in my case ride around kit, if it looks like it will cope with a bit of BIF then the Sigma 100-400 or the 300MM PF and TC.Alright. Let us know! Any other lenses on your radar? 300mm PF + 1.4/1.7 TC (and ftz) + Z50 could be a solid, small bodied, very high IQ combination.
Mike been watching your BIF for years. I'm an Oly guy who switched over to Nikon because Oly just didn't cut it with BIF. I bought a d500 and its a winner. I also own a z6 and was disappointed with it AF-C-----to be honest the tracking on the z series sucks. Its a great cam except for the shoddy AF system. It has great image quality, light weight, handles nicely,super sharp image with my 24-70 f/4, can use old glass with adapter------but for BIF ----UGGGGGGGGGG. Jus my opinion!!!