The royal tern (Thalasseus maximus ) is a tern in the family Laridae. The species is endemic to the Americas, though strays have been identified in Europe.
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. The breeding plumage of this bird 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, becomes fully white, while the crown becomes streaked with white. Its bill also becomes somewhat paler in the non-breeding season. Both the male and the female look alike.
Royal terns occur in both North and South America, as well as on Africa’s Atlantic coast. In the Americas, they can be found 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 are migratory and winter on the Pacific Coast, from Washington to Peru, and from Texas on the Atlantic Coast through the Caribbean and to southern Brazil. In Africa, Royal terns breed 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, these birds are typically found in inshore waters, lagoons, bays, harbors, estuaries, mangroves, and salt marshes. They nest on sandy, barren beaches, man-made islands, and offshore coral islands. Royal terns also like to rest on sandbars, beaches, mudflats, and are occasionally seen at inland lakes.
Royal terns are active during the day usually feeding alone or with a small group; they fly several meters above the water’s surface and then dive, but they do not submerge. They 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. Royal terns usually forage no more than 100 meters from the shoreline, but often this will be up to 30-40 km distant from the colony. They are gregarious, breed in colonies, and roost 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. Royal terns are territorial and will defend their 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 carnivores (piscivores). They eat fish that average 6-7 cm in length, squid, shrimps, and crabs.
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. Young birds usually become reproductively mature when they are 3 to 4 years of age.
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 the 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.
