Well black birds are called that for a reason!AFB, you got your lens…nice!
Just wondering what metering method you use. Matrix, centre-weighted or spot. This shot looks well exposed for the overall shot. For a dark coloured subject, the bird looks underexposed with too much detail lost in the deep shadow.
Shooting a dark subject may result in an overexposed background buts that's ok if you want your subject to show clearly. If your subject is the bird's overall environment, that's a different story.
If you haven't, try spot metering. The metered spot will move with your focus point on the D750. Meter and expose for the subject only and let the background be what it will be.
Spot metering for wildlife and matrix metering for landscape generally work well.
~ Peter
I was using centre weighted, but will give spot metering a try. Although shooting manual I guess it doesn't matter as much?
Thanks for the tips though (I could use them!).