Nikon D4, high iso and dynamic range

During gathering experience with my Nikon D810 and the 400mm tele lens, I was missing the bigger size, weight and the speed of a Canon 1D series camera. I don't like to use of any battery grips. Therefore I was looking for a second hand D4 or D4s. The fresh announced D5 would be perfect but is not yet available and too expensive for the moment.
I was happy to find a second hand D4 for 2200.- CHF in almost mint condition.
When I was shooting birds in Pontresina, I experienced exposure metering fluctuation. I learned that this is normal when shooting high speed and using spot metering because of the mechanical diaphragm lever. Due to this, some of my pictures were under exposed.
First I was a little disappointed, but then I realized, that this is not really an issue. I corrected it in my raw converter software and was surprised by the result.
Here are the pictures:
nature-pictures_ 176
Original exposure: ISO 800, 1/2500s, f/6.3 550mm

nature-pictures_ 177
Corrected picture: +2.0LV
nature-pictures_ 179
100% Crop, no color noise visible