The Royal Tern feeds mainly on small fish (3 to 18 cm, average 6 to 7 cm) as well as squid, shrimp, and crabs. In Africa, reported prey are mostly in the fish families Clupeidae, Mugilidae, Pomadasyidae, Carangidae, and Ephippidae. In Virginia, reported prey include Menidia, Fundulus, Anchoviella, and Brevoortia. In Florida, prey include Brevoortia and Micropogonias. In California, the Royal Tern relies heavily on Pacific Sardine (Sardinops sagax). (Gochfeld and Berger 1996) On the Atlantic coast of the United States, soft-shelled (newly molted) Blue Crabs are a major component of the diet (Kaufman 1996).
In a study of Royal Tern chick diet in Virginia, terns foraged largely on anchovy (Anchoa spp.) early in the season, then switched to herrings (family Clupeidae); average prey size also increased seasonally (Aygen and Emslie 2006). In a North Carolina study, systematic observations of adults returning with food indicated that at least 18 families of fish, squid, and crustaceans were exploited, the most common forage species in both years being anchovies (Engraulidae), herring (Clupeidae), and drum (Sciaenidae) (Wambach and Emslie 2003).
The Sandwich Tern (Thalasseus sandvicensis) and Royal Tern overlap in their distribution and often nest in the same colonies. McGinnis and Emslie (2001) studied the foraging ecology of these two terns in South Carolina and found that the two species partition food resources by spending significantly different proportions of their foraging time in different habitats and feeding on a significantly different set of prey.
Where the two species occur together, Kelp Gulls (Larus dominicanus) may steal food from Royal Terns bringing it back to feed their chicks (Quintana and Yorio 1999).
Eggs may be destroyed by sand crabs (Ocypoda arenaria). Black-headed Gulls (Chroicocephalus ridibundus) take both eggs and chicks, but Laughing Gulls (Leucophaeus atricilla) take only eggs. (Gochfeld and Berger 1996) At least occasionally, egg predation by Ruddy Turnstones (Arenaria interpres) may be quite severe (Loftin and Sutton 1979).
Dronen et al. (2007) described a new digenean trematode flatworm parasite from Royal Tern and provided a list of all parasites previously reported from this species.
The Royal Tern usually feeds singly or in small flocks, despite its tendency to roost in larger numbers. It typically flies 5 to 10 meters above the water and plunge-dives (but does not submerge). It also performs aerial skimming and surface-dipping for bits of food that may be floating on the surface. It occasionally steals food from other individuals. Most foraging occurs within 100 meters of shore, but it may feed up to 40 km from the colony. (Gochfeld and Berger 1996) It may sometimes feed at night (Kaufman 1996).
The Royal Tern (Thalasseus maximus) is a large white tern with an orange-yellow bill and a black crest. It is common along many tropical and subtropical shores of the Americas and West Africa. (Kaufman 1996; AOU 1998)
The Royal Tern is not globally threatened, although populations are declining in several areas. In the southeastern United States, numbers increased in the early 1900s (following a decline resulting from egg gathering for food) and the species slowly extended its range northward, breeding as far north as Maryland and, rarely, New Jersey. The East Coast population is about 34,000 pairs, the Caribbean population fewer than 1000 pairs, and the French Guiana (Cayenne) population is about 100 pairs, but the numbers of this tern in most of South America are not known. In California, the population crashed with the radical decline of the Pacific Sardine in the last decades of the 20th century. Around 25,000 pairs are believed to breed in Africa. (Gochfeld and Berger 1996; Kaufman 1996). Although the population numbers for most of South America are not well known, Yorio and Efe (2008) estimated the total Royal Tern population size as at least 750 pairs in Brazil and fewer than 5000 in Argentina.
In the New World, the Royal Tern winters from South Carolina and the Gulf Coast to Argentina, very rarely along the Peruvian coast. Chicks banded in South Carolina colonies were recovered mainly along the Gulf Coast, Florida, and the West Indies. Chicks banded in Virginia were recovered mainly in the Greater Antilles. West African birds disperse north to Morocco; most then move south to winter from Senegal to Angola, with smaller numbers south going to Namibia. (Gochfeld and Berger 1996)
In most of its breeding range, the Royal Tern is present year-round. On the Atlantic coast of North America, some birds wander north of the breeding range in late summer. In California, the Royal Tern is more common in winter than in summer. (Kaufman 1996)
In Africa, the Royal Tern breeds from Mauritania to Guinea, occasionally farther south, and winters south to Namibia. In the New World, it is found from southern California to Sinaloa and from Maryland (rarely New Jersey) to Texas and through the West Indies to the Guianas and possibly Brazil, with disjunct breeding populations in Yucatan and in southern Brazil, Uruguay, and northern Patagonia; it winters south to Peru and to Uruguay and Argentina. (Gochfeld and Berger 1996)
The Royal Tern breeds locally on the Pacific Coast of North America, in southern California, along the coast of Sinaloa and Sonora; in the Atlantic-Gulf-Caribbean region it breeds from New Jersey and the Gulf coast south through the West Indies to islands off the north coast of Venezuela and French Guiana, and in Yucatan; in South America, it breeds on the coast of northern Argentina; and in West Africa, it breeds on islands off Mauritania. Nonbreeders occur in summer in coastal areas in the Americas north to central California and Maine, and south through the wintering range (rarely on the Pacific coast south of Mexico). Wintering range is from central California, the Gulf coast, and North Carolina south along both coasts of the Americas to Peru, Uruguay, and Argentina; and on the west coast of Africa from Morocco to Angola (casually to southern Africa). (AOU 1998)
The Royal Tern is found on seacoasts, around lagoons and estuaries, and at sea over the continental shelf (AOU 1998).
The Royal Tern is found along tropical and subtropical coasts. It breeds on barren sandy barrier beaches, salt marsh islands, shell bars, dredge spoil, and coral islands. It shuns vegetation. Many colony sites are vulnerable to flooding. Breeding colonies typically are difficult to access (except by flight), offer high visibility, lack mammalian predators, and are surrounded by shallow water near the mouths of bays. It feeds around estuaries, lagoons, and mangroves. Outside the breeding season, it is found along coasts and and around estuaries, harbors, and the mouths of rivers, sometimes traveling a short distance up broad rivers. (Gochfeld and Berger 1996)
In North America, the Royal Tern is found along coasts, around sandy beaches, and in bays, lagoons, and estuaries. It may also be found well offshore and in the Caribbean frequently travels between islands. At least in North America, it is rarely found inland, except for a few interior localities in Florida. It typically nests on low-lying sandy islands. (Kaufman 1996)
The longest recorded lifespan for a Royal Tern is 17 years, but according to Gochfeld and Berger (1996) this is surely an underestimate.
The Royal Tern lays eggs in April to July in West Africa, in April in Texas, in May from Florida to Maryland, in June in Cayenne, and in November in Patagonia. Breeding colonies are dense and often quite large, frequently near Laughing Gulls (Larus atricapillus) or Sandwich Terns (Thalasseus sandvicensis). Most colonies contain 100 to 4000 breeding pairs. Density is about 5 to 8 nests per square meter. The Royal Tern occasionally nests singly in colonies of other tern species (usually at the edge of its geographic range). The nest consists of a simple scrape in the substrate (in Florida, it sometimes nests on rooftops). Clutch size is generally one (although adults have 2 brood patches), but 1 to 10% of birds may lay a second egg. Incubation period is 25 to 35 days. Young fledge at about 30 days post-hatching, but receive care from parents for 5 to 8 months and migrate south with them. First breeding is at 3 to 4 years of age. (Kaufman 1996; Gochfeld and Berger 1996)
Bridge et al. (2005) analyzed the mitochondrial DNA of a large fraction of the world's terns and correlated the results with plumage characters. Based on their new data on phylogenetic relationships among tern species, they suggested resurrecting several old genus names--including Thalasseus for the Royal Tern and several close relatives--to make nomenclature better match current understanding of relationships. This recommendation was endorsed by the American Ornithologists' Union Committee on Classification and Nomenclature (Banks et al. 2006), so the name Thalasseus maximus (Boddaert) for the Royal Tern is likely to be rapidly and widely accepted.
Mayr and Short (1970) considered the Royal Tern (T. maximus) and the Great Crested Tern (T. bergii) to together constitute a superspecies.
Yorio and Efe (2008) listed the threats to Royal Tern populations in Brazil and Argentina as human disturbance, fisheries, egging, and expanding Kelp Gull (Larus dominicanus) populations.
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.[2]
The royal tern was described by the French polymath Georges-Louis Leclerc, Comte de Buffon in 1781 in his Histoire Naturelle des Oiseaux from a specimen collected in Cayenne, French Guiana.[3] The bird was also illustrated in a hand-coloured plate engraved by François-Nicolas Martinet in the Planches Enluminées D'Histoire Naturelle which was produced under the supervision of Edme-Louis Daubenton to accompany Buffon's text.[4] Neither the plate caption nor Buffon's description included a scientific name but in 1783 the Dutch naturalist Pieter Boddaert coined the binomial name Sterna maxima in his catalogue of the Planches Enluminées.[5] The royal tern is now placed in the genus Thalasseus that was erected by the German zoologist Friedrich Boie in 1822.[6][7]
The generic name is derived from the Ancient Greek θάλασσα : thálassa meaning "sea". The specific epithet maximus is Latin for "greatest".[8]
The royal tern belongs to the class Aves and the order Charadriiformes. Charadriiformes are mainly seabirds of small to medium-large size. The royal tern is also in the family Sternidae because of its white plumage, black cap on its head, long bill, webbed feet, and bodies that are more streamlined than those of gulls.
The taxonomy of the royal tern has been debated, whether the correct scientific name was Thalasseus maximus or Sterna maxima. It is presently classified as Thalasseus maximus, which places it with seven other terns. The royal tern was originally placed in the genus Sterna; however, a 2005 study suggest that it is actually part of the genus Thalasseus.[9]
The West African crested tern (Thalasseus albididorsalis) was formerly considered to be a subspecies of royal tern. It was elevated to species status in January 2021.[10]
This is a large tern, second only to the Caspian tern but is unlikely to be confused with the carrot-billed giant, which has extensive dark under-wing patches.
The royal tern has an orange-red bill, pale grey upper parts and white under parts. Its legs are black. In winter, the black cap becomes patchy.[11] Juvenile royal terns are similar to non-breeding adults. Differences include juveniles having black splotched wings and a yellower bill. An adult royal tern has an average wingspan of 130 cm (51 in), for both sexes, but their wingspan can range from 125–135 cm (49–53 in). The royal tern's length ranges from 45–50 cm (18–20 in) and their weight is anywhere from 350–450 g (12–16 oz).[12]
The calls of the royal tern are usually short, clear shrills. Some of the shrills sound like kree or tsirr; the royal tern also has a more plover like whistle that is longer, rolling and is more melodious.[13]
In parts of its range, the royal tern could be confused with the elegant tern, but the elegant tern has a longer, more curved, bill and shows more white on the forehead in winter.
The royal tern is found on both coasts of the Americas. In the east during the breeding season (April to July) it is primarily found from Texas to Virginia. There are scattered breeding records as far north as Long Island, New York, coastally as far south as French Guiana, and on several Caribbean islands. Isolated breeding sites have been found in Argentina. The wintering range in the east is from North Carolina south to Panama and the Guianas and throughout the Caribbean. The western population nests from California to Mexico and winters from California south to Peru. Argentinian breeders may disperse into Brazil.[2]
The royal tern typically feeds in small secluded bodies of water such as estuaries, mangroves, and lagoons. Also, but less frequently, the royal tern will hunt for fish in open water, typically within about 100 metres (110 yards) of the shore. The royal tern feeds in salt water and on very rare occasions in fresh water. When feeding they fly long distances from the colony to forage.[2] The royal tern feeds by diving into the water from heights near 30 feet (9.1 metres).[14] They usually feed alone or in groups of two or three, but on occasion they feed in large groups when hunting large schools of fish.[2]
The royal tern usually feeds on small fish such as anchovies, weakfish, and croakers. Fish are their main source of food but they also eat insects, shrimp, and crabs.[2][15] The royal tern feeds on small crabs, such as young blue crabs that swim near the surface of the water. When feeding on small crabs the royal tern does not use its normal plunge-dive technique, but instead uses short shallow dives so that they are concealed from their prey. The royal tern also uses this technique when hunting flying fish.[2]
The royal tern nests on island beaches or isolated beaches with limited predators. It lays one or two eggs, usually in a scrape, an area on the ground where a tern has made a small hole to lay its eggs. In some cases, tern eggs are laid directly on the ground, not in a scrape. The eggs incubate from 25 to 30 days; after the eggs hatch the chicks remain in the scrape for about a week. About two weeks after hatching the chicks gather into groups called a crèche.[14] When the chicks are in the crèche, they are primarily fed by their parents who recognize their offspring by their voice and looks. While the chicks are in the crèche, they usually roam freely around the colony. In a large colony there can be thousands of chicks in the crèche.[2][16] When the chicks are a month old they fledge or start to fly. Royal terns mature around the age of 4 years, after which they build their own nests and reproduce.[14]
The royal tern has few predators when it is mature, but before the chicks hatch or while they are chicks the tern is threatened by humans, other animals, and the tides.[17] Humans threaten terns by fishing and by disrupting the tern nesting sites. Fishing nets can catch a tern while it is diving, making it unable to feed or it may cause it to drown if it is caught under water. Animals such as foxes, raccoon, and large gulls prey on tern chicks and tern eggs.
Tern nesting sites can also be affected by the tides; if a tern colony has nested too close to the high tide mark a spring tide would flood the nesting site and kill the chicks and make unhatched eggs infertile.[17][18]
A Tern was documented with a wing broken in three places near the launch site of the recent SpaceX Starship. A local vet at the zoo calls this a common injury. The bird was found 53 hours after the launch hurled concrete and rocks into the area. The Zoo vet says the injury could not have been caused by the debris as the animal would have been removed by predators. This would have been the only bird alive injured after the launch. Reference injury report, 04/22/23 Brownsville Zoo.
The IUCN has rated the royal tern as of Least Concern.[1]
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.
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