The Nikon D810 arrived yesterday afternoon so I had to test it at the tree in the lake this morning.
Seems in good working order. The Great Blue Heron like it, as best I can tell.
I can now retire the D800. That leaves me with a three body field kit for this summer.
Nikon D7200, Nikon D750 and Nikon D810.
The D850 will have to wait a couple of years. Should be off back-order by then.