Hawk Deterrents - the Hawk Ball

Racing fancier John Glemser discusses his use of "Hawk Balls" to try to deter hawks from attacking his Racing Pigeons. He remarks that after having done a lot of research, he believes that the placement of shiny objects such CDs helps to prevent hawks from attacking his pigeons.

You can obtain commercially produced "bird deterrents" from Amazon.com such as those below. Do they work? Who knows? But, it can't hurt to try.