The Royal tern is the second biggest tern after the Caspian tern. In flocks of terns and gulls, it is usually easily identified by its size, its characteristic black crest and its bright orange bill. It lives only along ocean beaches. The breeding plumage is a black crown with a distinctive black shaggy crest. In the basic plumage, its forehead as well as the area between its eyes and bill become fully white, while the crown becomes streaked with white. Its bill also becomes somewhat paler in the non-breeding season. Both genders look alike.
The Royal tern occurs in both North and South America, as well as on Africa’s Atlantic coast. In the Americas, it occurs from southern California through to the Yucatan Peninsula and Mexico, on the Gulf and Atlantic coasts of the U.S. and the Caribbean, and also in south-eastern South America. These birds winter on the Pacific Coast, in Washington to Peru, and from Texas on the Atlantic Coast through the Caribbean and to southern Brazil. In Africa, the royal tern breeds on the west coast from Mauritania to Guinea, and winter from Morocco and the Straits of Gibraltar to Namibia. African populations may be vagrant within Europe. Primarily a coastal species, this bird is typically found in inshore waters, lagoons, bays, harbors, estuaries, mangroves and salt marshes. It breeds on sandy, barren beaches, man-made islands and offshore coral islands. Royal terns rest on sandbars, beaches and mudflats, and are occasionally seen at inland lakes.
The Royal tern is a diurnal animal and it feeds alone or with a small group, by flying several meters above the water’s surface and then diving, but it does not submerge. It may also perform aerial skimming to scoop up offal by surface-dipping, and will also take food from other terns; other seabirds do this too. The Royal tern usually forages no more than 100 meters from the shoreline, but often this will be up to 30-40 km distant from the colony. This bird is gregarious, and breeds in colonies and roosts in flocks. The colonies may number hundreds, or sometimes thousands of pairs, and this is good protection against predators from the air, as these cannot land within the colony. This species is territorial and will defend its small space by flying or walking or towards intruders, by flutter flights, aerial chases, and a number of displays involving head movements.
Royal terns are monogamous, but it is not clear whether such pair bonds are maintained between seasons. African and North American populations typically breed from April to August, and in South America it is between October and March. Their courtship displays take place either on the ground or in the air. Usually, a male will bring a fish to the female. She either swallows it immediately or keeps it in her bill during the displays. After establishing a pair bond, the birds will together select a site for their nest, circling the chosen place several times. Their nest is just a simple shallow scrape on the ground. These terns nest in a large, dense colony of several thousand pairs, and often there are gull species amongst them. Nests are 5 to 8 per sq. m. One egg is laid and incubation is for around 25 to 31 days, by both parents. Both adults have brood patches. Soon after hatching, chicks join a crèche or group with other young on the beach. They fledge about a month after hatching, but still depend on their parents until they are 5 to 8 months old. They are reproductively mature at 3-4 years.
The Royal tern is currently not considered to be under threat of extinction. However, its preferred breeding sites are often at risk of flooding, and a potential threat is contamination of its prey by pesticides. Other threats involve: overfishing, human disturbance at nesting sites, egg collection, oil spills and discharge of chemicals and sewage into the sea, especially in the Rio de la Plata area in Argentina and Uruguay.
This species has a very large range, but the IUCN Red List and other sources do not provide the Royal tern total population size. According to the All About Birds resource, the total breeding population size of the Royal tern on the North American continent is 100,000-150,000 birds. Currently this species is classified as Least Concern (LC) and its numbers today remain stable.