Royal terns subsist primarily on small fish, four inches or less in length, which they seize by hovering in the air and then diving into the water below. Crabs are another favorite food, as are oysters. Sometimes royal terns will fly close to the sea’s surface, scouting for schools of small fish and then dipping their bills repeatedly into the water to secure their meal.
The large (18 to 21 inches long) and striking royal tern is easily recognized by its size, white body, pale gray wings, crested black cap, and orange bill. The only bird it may be confused with is the even larger Caspian tern, but that bird has a blood-red bill and no visible crest. Royal terns are graceful fliers for their size. Slim, with long, pointed wings and a wingspan that reaches nearly 4 feet, they have delicate, deeply forked tails and are well designed for life on the wing.
I spied on this tern from the east causeway a few days ago.