Drumming

Hi, Has anyone come across birds drumming? I have, until recently,only seen it once before. The drummers, i.e. rapidly lifting one leg after the other, were herring gulls. This was inland and they were drumming on a lawn in the middle of a roundabout. I do not know but my guess was that this brought the earthworms to the surface for a quick snack. Now this one I cannot work out. Collared doves are doing it on a six foot high wooden fence. This is now a daily event before they come into the garden looking for seeds. Any ideas community? Regards, Hooky.