Bill_de wrote:
If you are going mirrorless, wait for the appropriate Z mount zoom.
If you are shooting with an F mount lens (or want to use an adapter) the Nikon 500mm F/5.6 is a reasonably affordable option. Hang onto the 200-500 for when you really need a zoom.
Sticking mostly with F mount bodies, when I get back into the field for wildlife the Nikkor 500mm F/5.6 and the Nikkor 300mm F/4.0 will be my most used lenses. The D500 and D850 are still my favorite bodies.
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Nikons f mount bodies are some of the best cameras in the world. I see no reason to go out and chase mirrorless.