беркуты/Golden eagle filmed in Sweden 2023, 4K 120fps

This is the first time I am trying Canon 400mm f2.8 rf, I have tried to used it before but no success with birds/animals unfortunately. It’s a beast of a lens and I really dont have anything to complain on, maybe there is no built in 1x.4 extender like there is on the new Nikon 400mm 2.8. But yeah, I dont mind it! I went from 600mm f4 to 400mm , just to be able to shot it 2.8. it makes a big difference when it’s darker outside. Would you choose f4 or 2.8 ? reach vs light, let me know in the comments!