Hand holding or mono-poding a 600mm is like shooting a rifle at long range. I exhale slowly and squeeze, slowly and gently.
Birding guides typically carry a tripod with spotting scope attached, with DSLR and 600mm lens hanging on a shoulder strap. If said camera is set to rapid fire each time the shutter is pressed a barrage of 6 or more photos is produced for each press. Of which one or two might be in sharp focus. If ISO is high enough.
Shooting (photographing) birds in flight is like swinging a shotgun (I don’t anymore but I once did). Relax your arms arms, exhale, swing. Shoot. Never ever pause. Once the swing starts keep it moving until you click!
For this one I had to raise camera and monopod together, and swing them both.
