Every day is a bad hair day for a Royal Tern. These large terns have a spiky crest that lifts up in the wind and at times seem to have a life of its own. To match the “punky” hairdo, they have an orange bill. Perhaps it is the crest that has earned these terns the name “Royal Tern.” The breeding adults have a black cap that extends from the top edge of the bill to the crest. As the nesting season progresses, the forehead becomes more white and remains so through the non-breeding season, leaving what looks more like a mask.
In non breeding birds there is a white eye ring in the black mask and the forehead is white. The Juveniles and non breeding adults look similar; they have a black crest, but lack the full black cap. In all birds the legs are dark and the tail is long and moderately forked. The bill on the juveniles is a bit smaller and pale yellow.
What do you need to look at when you see a tern? You do not have to remember everything about a bird, the trick is to know what to look for and remember the key field marks. Each group of birds has its own.
When I first see a tern, I look for the color of the bill and feet and try to determine the shape of the tail. Some terns have very long forked tails; others have shorter tails with a small V like fork. Royal Tern tails fall somewhere in the middle. On my second look, I try to find any distinctive wing or tail patterning. Most terns are shades of white, gray and black, but there are many wing patterns that can help you sort our which species you are looking at.
For example, royal terns look a lot like Caspian Terns, but the latter has a lot more black on its wings. Caspian Terns are very rare in the Greater Antilles and do not occur in the Lesser Antilles. A bird book is very helpful for sorting out what is likely to occur in your area.
Royal terns have a very large range. They breed on the east coast of the United States, all the way through the Caribbean and south to Argentina. Their winter range overlaps much of the breeding range. They also nest irregularly along the southern California coastline of the Pacific Ocean. Royal Terns are locally common in the Greater and Lesser Antilles. A second subspecies of Royal Terns is also found on the western side of Africa and may reach as far north as Spain. Unlike many species of terns who feed in both salt and fresh water, Royal Terns feed only in salt water environments.
Terns have a distinctive way of hunting—they look down while they are searching for food and hover for a moment before they dive into the water. At times, the dive is so fast and powerful they look like someone has thrown a dart into the water. Royal Terns dive from heights up to 30 feet. Their diet consists predominantly of small fish, squid, shrimps and crabs. Royal Terns can be seen feeding alone or in small flocks. Feeding adults normally wander up to 40 kilometers from their colony
Royal Terns nest in dense colonies that can number into the thousands. Colony sites are quite varied, but isolation, good distance visibility and absence of mammalian predators are essential prerequisites. The nest is an unlined shallow depression in the sand. The pair defecates directly on the nest rim, perhaps to reinforce the nest against flooding. Like most terns, Royal Terns fiercely defend their nest and young.
Royal Terns lay one and rarely two buff or whitish colored eggs with brown blotches. The egg is incubated for 30-31 days and both parents incubate. The chicks hatch with downy feathers and are mobile only hours after hatching. Chicks will remain at the nest for up to a week unless disturbed. By two weeks of age, most young gather together in a large mobile group known as a crèche. While in the crèche, chicks are normally fed only by their parents, who identify their young by vocal and visual characteristics. The function of the crèche is to make it more difficult for predators to pick out one chick to prey upon. The main threat to Royal Terns is mammalian predators and development on or near their nesting sites.
Devi Sharp is a retired wildlife biologist and is exploring the birds of the Caribbean with her husband, Hunter, on their sailboat Arctic Tern.
Chuck Shipley is a former professor of computer science and an avid amateur photographer. He and his wife Barbara live aboard their trawler Tusen Takk II in the Caribbean.