Would switching over from the D7200 DX format to the new Z5 full frame format be considered an upgrade for bird shots?
For bird shots (where focal length of the lens plays a huge part), I can't see how how it can be any sort of a real upgrade.
There are no suitable native Z mount long focal length lenses (and who knows when they will inevitably appear in this climate - could be half a dozen years ? Canon has their new 600 & 800mm f11's ! as competitive impetus, but whether they are going to be useful for birds, especially BIF is unknown at this point), so it will be adapted F mount long lens on any Z5 for the foreseeable future.
The main drawback as far as I can see is that you lose resolution/focal length by not having the crop factor of the D7200.
Both cameras are 24MP, but your 400mm lens (say) gives a 50% larger 600mm size image on the D7200, etc. Photographic dynamic range also favours the D7200 by the time you have cropped a Z5 image to the same subject image size.
The D7200 shoots at 6fps (and 7fps in 1.3x in-camera crop mode which I find very useful) vs 4.5fps of the Z5.
AF is another area to consider. I haven't heard reviews of the Z5's performance yet, but it think it is likely to have a similar fiddly initiation to other Z cameras. I think on balance it's likely to prove to be another area where the D7200 comes out on top.
I think the Z5's strength is as an entry level FF mirrorless walkaround street camera, portraiture, etc.
The time to change might be one day, but I don't think it is any time soon.
Chosun :gh: