Saw something yesterday that was a first for me. While out driving, I saw a red tailed hawk doing some 'aerials' and repeated circling along a tree line. I could see a 'patch of brown' toward the end a limb on a large oak tree. Suddenly, the hawk 'attacked' the brown patch in flight and kept moving. I stopped to watch as he continued circling the tree several times. By now, I had figured out that the brown patch was several dead leaves, roughly the size of a large fox squirrel. After a few more aerial 'flips and antics', the hawk again honed in on the brown leaf patch. This time, he hit it hard enough to knock several leaves free of the branch. I kept wondering why he would do this, as it was obvious he knew it was dead leaves and not a live prey. This morning, thinking it over, I'm now thinking that perhaps he was opportunistically practicing his skills by using the appropriately sized patch of leaves as a target simulating a squirrel as prey. Has anyone else observed this sort of behavior, or know what else he might have been doing? It was fun to watch!