Hi -- The answer is, they do not -- the sounds are, in the vast majority of cases, added afterwards. Sound technicians have a wide variety of tricks to mimic whir of wings, flapping, footsteps, etc. Once I watched a very good film of a leopard walking through grass, and it crunched, crunched quite loudly -- although I strongly suspect that in real life it was completely silent like the leopard we saw (but did NOT hear) walking through dry grass last December in Africa. Either Discovery or Nature had a program where top wildlife photographers displayed their techniques, which included editing tricks and sound dubbing. Sometimes background sounds are recorded at the same time and remixed into the final video, as well. But I suspect the wing flapping was added in the studio. Gail Mackiernan