Good point it depends how close. I thought if the lens is top quality after shot cropping would mean less artefacts. Perhaps.
Anyway distance has been from 25m to about 400m away. I suppose video would also be used,on the D500. I have a few toys like the Panasonic Fz200 but quality is no where good enough Imho.
Hence the D500 route. The Panasonic is a fixed f2.8 Leica lens.
Last winter on my D500 I used a Tamron 150-600 v2 but doesn’t like low light.
Also have a Nikkor 70-300 f4.5-5.6 G Ed vr lens.
The new lighter Nikon lenses are utter rubbish for this sort of photography imho suited mainly to tourist stuff in strong light.
The Tamron can give superb results right up until the light drops, which is when the birds Flock.