Doc the go to body the right body is def the one in your hand when one is in the right place at the right time I know you are sorted but hell I just thought a definitive answer might be fun.
Regarding lens....and( the above) I don't shoot nik so can't really help much,
Honestly I'd ask questions of meself and base my choice on that.......mainly birdz...........big bird small birds? a biggy how close can I get? how strong am I? Do ya want to hand hold or is a tripod your thing how much light do I shoot under can I work with really high ISO? Zoom or prime
Buddy if one can't carry the gear ,too heavy , one is miserable if one can't get close categorically one needs reach....so one can miitigate reach so some extent with what togs call field craft, but one can't do that in many circumstances.
Adam there is a whole plethera of choice in all this, I guess what I'm trying to get out is you need a tool for a job, simplicity.you need the right lens tool) for your style of making images You need to meld that tool to your specific needs.
Mate I largely shoot with one lens in an ideal world, for wildlife, I'd have probably 3 or 4 lenses.................... but I can't afford that hell I couldn't afford what I have.............. just crunched hours to make it possible.
I bought what I honestly thought suited my needs. It is silly sharp if I do my bit, I rarely measure up to my gear but if one is picky about one's images then that is no bad place to be.
Adam go slow on lens choice if you can't have many.......... really think about what you personally need. the images you want to make, tailor the glass to you.
Bless ya for being a Dr
take care
stu