Today a flock with several dozens of dunlins (including a few little stints and grey plovers) can be approached at the beach of Principina. I've crawled reasonably close to them to frame small groups with the longest focal I have (300mm * 1.7 = 540mm). But I've also prepared the second body with the 180mm which would give me a broader view of the flock.
Two minutes ago I've spotted at a distance two hikers and their dog, getting closer; I've prepared the second camera with the 180mm pre-focused, in order to get most of the flock anticipating that the hikers will probably scare the birds to fly away. Which unfortunately just happened, preventing me from enjoying the birds for a longer time, but I've been able to shoot three photos of the flock in flight, one of which is pretty good.