These terns go nuts when the skimmers come too close to their chicks/nest. This behavior always makes for good photo opps. They love to "dive bomb" the skimmers.
I like the open bill and the dangling feet. The bird is placed nicely in the frame. It looks like the nictating membrane is covering the eye. I might have pushed the exposure a little further to the right; not a lot of detail in the blacks.
I like the pose, BG and composition. I don't know if you can get more details in the eye but it would make it even stronger. I would also run NR on the BG.