I write again and again about R5/100-500 not being the ideal combo for me for BIF. I have my first example because I understand it is tiring for people to read again and again the same thing.
I was able to get only one out of more than 10 shots and that in 135mm setting. There maybe technique issues for the low success rate buty anyway here it is:
The above is inserted at 100% crop (1920x1280 jpeg).
In contrast when a common buzzard flew in front of me while I was driving my D500/500mmPF combo did the job instantly although I was not paying attention at that moment:
The above is inserted smaller. Below a 100% detail:
I had to go to the dentist for a root canal this morning. Never go anywhere without your RF 100-500mm (or equivalent) on your R5 (or so) in your car, where you have wait in Covid times. The dentist had to drag me from the car park as a Buzzard (Buteo Buteo, not US buzzard) flew overhead just as I was due to go in.
Spent a few evenings sitting in the sand near a group of Black Skimmers. At one point while the late evening clouds parted for a few minutes, about half of the group took off and this was one returning in the bunch. Of course it would be banded... lol.
It's taken me a year to find out how good the RF 100-500mm is with the RF 2x zoomed out to 600mm as I have tended to use the lens either native or fully zoomed in to 1000mm. Here are some practice shots at 600mm on the R5 of a juvenile Gull, and also a Blackheaded gull shot through some bushes, showing that tracking is sticky on the white contrasty subject. The gifs show how well the tracking is in general.
A couple of different type of shots. A close up of a Blackheaded Gull in flight at 1000mm/R5. Then, a small raptor was wheeling very high up, which on downloading and lightening was seen to be a Sparrowhawk (enlarged 2x).