These are Snowy Egrets showing their plumage during mating/breeding season. They start to show in March and keep their feathers for quite a while. Their beaks turn more of a yellow/orange color during the season. You will find these birds in shallow salt and fresh water areas with a small flock wading and dancing about. They will approach one another, start squawking, inflate their feathers and chase each other about. Sometimes they will start jumping in the air flapping their wings and dance around one another until one gives up and backs off. You will also find them among other herons and wading birds during this time, and occasionally they will mate with other herons.
Snowy Egrets at one time, early in the 20th century, were endangered. Their breeding feathers were used for hats and were valued at twice the price of gold. The fact that they build their nests close to the ground and are easy to catch didn’t help. It was only through conservation efforts that they came back and are now considered quite common.