Roberta, yeah, the thumbnail picture of the Rock Beauty looked like a Cockatoo.
Crown of Thorns Starfish.
This starfish has very sharp spines packing a painful venom. It feeds on coral leaving behind nothing but the white calcium carbonate skeleton. When I was on Guam in the late sixties, there was a huge population bloom of these starfish which caused considerable reef damage.
One of it's few natural predators is the Triton's Trumpet.