Thanks Klaus. I found that the only way I could get them was by anticipating thier movement - they tend to systematically fly round the flowers, and its sometimes possible to anticipate where they will go next. I also found that I can't shoot them with the Z6, but the D500 works well, as one would expect.Jeff, it's a fantastic picture.
Shooting them is difficult if not impossible.
The only chance is in front of a blossom.