Thanks very much Paul. Yes, I am using that Auto-ISO Auto feature of the D4, where if I am on tripod I set it to one "notch" lower which gives a 1/focal length less one stop (e.g. 1/320 with the 500VR plus TC14), or default middle notch if I am trying to stop the motion of a bird that is singing as in the 2nd last photo, or one or even two notches higher for Birds in Flight (BIF).
All the woodpecker photos are 500VR with the TC14 and all the rest are TC17 and many of these are wide-open which is not ideal in a theoretical sense, in that one should stop-down TCs, but it seems if I nail focus is not a problem.
My D300 has been my first casualty, I sold it two months after getting the D4, as you indicate you can't be cavalier about ISO with that camera, although it was very good in its day. It was a great workhorse for me with 72K actuations, so I got my money's worth. It went to a very knowledgeable young photographer who was getting back into serious shooting after a hiatus. I am thinking a D400 in good light combined with a D4 in tougher light will eventually give me a very nice capability for my wildlife outings.
If I am going to make a habit of FX bird photography I might need one of those new 800mm lenses Nikon has over at the British Open