Came across this thread while looking for somewhere to post my first shots of bird shooting on - but having found it I felt intimidated as the pictures where much better than mine!
Had brought out my Voigtlander 180 mm / 4 for a jaunt to try it out - I really don't use it enough. Came into a grassy area where they were some birds flying about, so tried my hard at shooting them. Quite tough, mainly because of 3 factors: (i) using an MF lens, (ii) the very stiff focusing ring of the Vt180 - apparently a common characteristic for this lens, and (iii) being too near the birds - they were buzzing around directly overhead, say 10 - 15 m away.
These are the 2 best shots of the day, but even then the focusing was slightly off.
Will try more bird in flight photography, but would like to ask what is the distance to shoot birds in flight at?