Even as a kid I noticed mocking birds would walk around in the grass or in fields and stand tall spreading their wings a few moments and then lower them. Then they would walk a short distance and do the same thing again. I also noticed when the bird spread its wings the grass hoppers would fly or jump and the bird would run over and get them. I just supposed by nature or mimicking the bird learned when they raised and spread their wings the bugs thought maybe they were about to be pounced on so a bunch would take flight or run to escape at one time. But in so doing they gave away their hiding place and made it easier to be caught. I never saw other birds do this though.