I would love to know your go-to AF and other settings. The birds are consistently razor sharp.
Sure. I always use either single point or auto area with my D500. Shutter speed and aperture vary according to conditions, but I use the fastest shutter speed I can "get away" with. For birds in flight in good light I go 1/3200 most of the time. With stationary subjects I still use 1/2000 or even faster if I can, because stationary subjects often turn into moving subjects very quickly.

Of course, in low light all of this changes. With owls before sunrise, for example, I have gone as slow as 1/8 second and pick through a lot of shots to find a sharp one. I use auto-ISO, keeping an eye on things and using exposure compensation as needed. Aperture wide open in low light, but f/7.1 or so in good light for a tad more DOF and a slight improvement in sharpness. I close down more if I need the DOF when there are multiple subjects in the frame. . Most of the shots I post here are with a 500 PF lens, which I find to be a very sharp lens. The Denoise software available these days has certainly made a big difference.