I managed to capture this one from the old city walls at Dubrovnik in Croatia, on my recent holiday. I am glad I never took the 500mm or I would be spending far too much time on these birds. It was spectacular, the Alpine Swifts would show about an hour before the sun went down, their aerial display and calls were stunning.
Lovely shot Will,I remember these birds doing just as you describe turning up about the same time each evening over the White mountains in Crete,a real treat to witness.Sounds like a good trip even without the bid stuff.
Very nice image. I love the in unison flock and the colorful background. If mine I would try a version where I cloned out the 2 birds on the far left that don't have the same angles as the rest of the birds. Then I would take a bit off of the left and add to the right to give some more room for the birds to fly into. Not sure it would be better than how it is presented but worth a try.