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)
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) BREEDS: locally on Pacific coast in southern California (rarely, not in recent years) and western Mexico (coast of Sonora and Sinaloa, Tres Marias Islands); Gulf coast and Maryland south through West Indies (where breeding irregular in location, year, and number of pairs; van Halewyn and Norton 1984) to northern South America (northern Venezuela and nearby islands, French Guiana), including cays in Puerto Rico and Virgin Islands; Uruguay coast and northern Argentina; West Africa. Possibly 80% of the world population breeds in the southeastern U.S. Nonbreeders occur in summer north to central California and New York, south through winter range (rare on Pacific coast south of Mexico). NORTHERN WINTER: north to central California, Gulf coast, and North Carolina, south along coasts to Peru, Uruguay, and Argentina; west coast of Africa.
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)
Length: 51 cm
Weight: 470 grams
Differs from the caspian tern in having a thinner bill, underside of primaries mostly pale (vs. dark), a more deeply forked tail, and, in basic and immature plumages, a white crown and forehead (vs. dusky). Differs from elegant tern in larger size (average length 51 cm vs. 43 cm), thicker bill, less slender body, and (in nonbreeding plumage) usually lack of dark feathering contacting the eye. Averages at least 12 cm longer than other North American terns.
Habitat and Ecology
Comments: Seacoasts, lagoons, estuaries, rarely on lakes (AOU 1983). Loafs and sleeps on mudflats, sandspits, or salt-pond dikes (Stiles and Skutch 1989).
Nests typically on open sandy beaches of barrier islands, sandbars, sand/shell substrates; also on newly created dredged-material islands (Spendelow and Patton 1988); on remote cays in Puerto Rico and Virgin Islands. Colony site requirements: absence of quadruped predators; isolation from disturbance, combined with excellent visibility; proximity to areas of extensive shallows; and proximity to oceanic inlets (Buckley and Buckley 1984). Colonies in the eastern U.S. regularly change location (Buckley and Buckley 1984).
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)
Water temperature and chemistry ranges based on 225 samples.
Depth range (m): 0 - 0
Temperature range (°C): 9.208 - 27.517
Nitrate (umol/L): 0.240 - 3.829
Salinity (PPS): 32.282 - 36.362
Oxygen (ml/l): 4.518 - 6.764
Phosphate (umol/l): 0.057 - 0.547
Silicate (umol/l): 0.769 - 3.817
Temperature range (°C): 9.208 - 27.517
Nitrate (umol/L): 0.240 - 3.829
Salinity (PPS): 32.282 - 36.362
Oxygen (ml/l): 4.518 - 6.764
Phosphate (umol/l): 0.057 - 0.547
Silicate (umol/l): 0.769 - 3.817
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Migrants in South America occur mostly October-early May (Hilty and Brown 1986).
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)
Comments: Eats mainly fishes up to about 10 cm long, caught by plunging into water while flying (Bent 1921, Terres 1980). Fishes well out from shore beyond breakers (Stiles and Skutch 1989).
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.
Nonbreeding: often in large flocks when resting on land; often in large mixed flocks when migrating.
Life History and Behavior
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 longest recorded lifespan for a Royal Tern is 17 years, but according to Gochfeld and Berger (1996) this is surely an underestimate.
Lifespan, longevity, and ageing
Lays clutch of usually 1 egg, May-June in southeastern U.S. and Puerto Rico/Virgin Islands, April-June in Texas. Incubation lasts 20-22 days (reported also as 28-35 days), by both sexes. Young are tended by both parents, flock with other young at 2-3 days, fly at 4-5 weeks. Usually nests in dense colony; colony size commonly over 1000 in most areas in U.S., some colonies >10,000 in South Carolina, Texas, and Louisiana (Spendelow and Patton 1988).
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)
Evolution and Systematics
Systematics and Taxonomy
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.
Molecular Biology and Genetics
Barcode data: Thalasseus maximus
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Thalasseus maximus
Public Records: 7
Specimens with Barcodes: 10
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N5B,N5N : N5B: Secure - Breeding, N5N: Secure - Nonbreeding
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: Large range; relatively stable populations in major nesting reagion in the southeastern U.S. Sensitive to disturbance when nesting.
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.
Comments: Routinely deserts colony en masse and moves to new site if disturbed early in egg-laying period (Buckley and Buckley 1984).
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.
Needs: In Culebra Archipelago (Puerto Rico), colonies are in need of protection from illegal human harvest of eggs, which in some years has resulted in total failure of nesting effort (Wiley 1985).
The royal tern (Thalasseus maximus) is a seabird in the tern family Sternidae. This bird has two distinctive subspecies: T. m. maximus which lives on the Atlantic and Pacific coasts of the North and South America, and the slightly smaller T. m. albididorsalis lives on the coast of West Africa. The royal tern has a red-orange bill and a black cap during the breeding season, but in the winter the cap becomes patchy. The royal tern is found in Europe, Africa, the Americas, and the Caribbean islands. The royal tern lives on the coast and is only found near salt water. They tend to feed near the shore, close to the beach or in backwater bays. The royal tern's conservation status is listed as least concern.
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 five other seabirds from the tern family. The royal tern was originally placed in the genus Sterna; however, a 2005 study suggest that it is actually part of the genus Thalasseus. The royal tern is currently divided into two subspecies: Thalasseus maximus maximus and Thalasseus maximus albididorsalis. T. m. maximus is found on the East Coast of North America and is referred to as the "New World" species. T. m. albidorsalis, referred to as the "Old World" species, is found on the Atlantic coast of North America, the Caribbean Islands, the East Coast of South America, and in the West coast of Africa.
This is a large tern, second only to 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. 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 average weight is anywhere from 350–450 g (12–16 oz).
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.
In various parts of its range, the royal tern could be confused with the elegant tern, lesser crested tern (the other orange-billed terns), and the greater crested tern. It is paler above than lesser crested tern and the yellow-billed great crested tern. The elegant tern has a longer more curved bill and shows more white on the forehead in winter.
Habitat and range
In the Americas, the royal terns on the east coast, during the breeding season (April to July), occur in the US north to Virginia, occasionally drifting north to Maryland. The southern end of their breeding range is Texas. The wintering range for on the east coast is from North Carolina south to Panama and the Guianas, also the Caribbean islands. On the western coast of the Americas, the royal tern spends the breeding season from the US state of California to Mexico, wintering from California south to Peru.
In Africa, the royal tern is found along the west coast in the islands off the coast of Mauritania during the breeding season, but it is believed that there are undiscovered colonies on the west coast near or in Nigeria. The royal tern usually winters from Morocco south to Namibia. The royal tern is not usually found in Europe although it has been seen in Spain and Gibraltar. There have also been unconfirmed sightings farther north in Europe.
American birds migrate south to Peru and Argentina for the winter to escape the cold weather. African breeders move both north and south from the breeding colonies. African birds may reach as far north as Spain. This species has also wandered to Western Europe as a rare vagrant, these terns are probably from the American colonies.
The royal tern typically feeds in small secluded bodies of water such as estuaries, mangroves, and lagoons. Also, but less frequently, the royal terns will hunt for fish in open water, typically within about 100 metres (110 yards) off 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. The royal tern feeds by diving into the water from heights near 30 feet (9.1 metres). 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.
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. 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.
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. 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. 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.
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. 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 to close to the high tide mark a spring tide would flood the nesting site and kill the chicks and make unhatched eggs infertile.
The royal tern is one of the species addressed in the Agreement on the Conservation of African-Eurasian Migratory Water Birds (AEWA). The AEWA covers 255 species that depend on wetlands for part of their life. The AEWA covers birds from 64 countries in Africa and Eurasia. There are little other conservation efforts because the royal tern's status is of least concern. The reason there is little concern for the extinction of the royal tern is that the species has not experienced a significant enough decrease in population to become threatened or endangered.
- BirdLife International (2012). "Thalasseus maximus". IUCN Red List of Threatened Species. Version 2014.2. International Union for Conservation of Nature. Retrieved 1 September 2013.
- Bridge, Eli S.; Jones, Andrew W.; Baker, Allan J. (2005). "A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution" (PDF). Molecular Phylogenetics and Evolution 35 (2): 459–469. doi:10.1016/j.ympev.2004.12.010. PMID 15804415.
- Buckley, P.A.; Buckley, Francine G. (2011). Poole, A., ed. "Royal tern". Introduction. The Birds of North America Online. doi:10.2173/bna.700. Retrieved 13 December 2011.
- "Royal tern (Sterna maxima)". Planet of Birds. Retrieved 17 November 2011.
- "Royal Tern". All About Birds. Cornell Lab of Ornithology.
- Pough, Richard H. (1951). Audubon Water Bird Guide. Doubleday & Company, Inc. pp. 291–292. ISBN 0-385-06806-9.
- Buckley, P.A.; Buckley, Francine G. (2011). Poole, A., ed. "Royal tern". Distribution. The Birds of North America Online. doi:10.2173/bna.700. Retrieved 31 December 2011.
- Buckley, P.A.; Buckley, Francine G. (2011). Poole, A., ed. "Royal tern". Food Habits. The Birds of North America Online. doi:10.2173/bna.700. Retrieved 18 December 2011.
- Clay, Roger (October 2006). "Royal tern". Alabama Department of Conservation and Natural Resources. Retrieved 7 November 2011.
- Favero, Marco; Silva R., M. Patricia; Mauco, Laura (1 June 2000). "Diet of royal (Thalasseus Maximus) and sandwich (T. Sandvicensis) terns during the Austral winter in the Buenos Aires Province, Argentina". Ornitologia Neotropical (The Neotropical Ornithology Society) 11: 259–262. Retrieved 7 November 2011.
- Buckley, F.G.; Buckley, P.A. (3 April 2008). "The breeding ecology of royal terns Stena (Thalasseus) Maxima Maxima". Ibis (Wiley Online Library) 114 (3): 344–359. doi:10.1111/j.1474-919X.1972.tb00832.x. Retrieved 8 November 2011.
- Yorioa, Pablo; Amorim Efe, Márcio (2007). "Population status of royal and cayenne terns breeding in Argentina and Brazil". Water Birds (The Waterbird Society) 34 (3). doi:10.1675/1524-4695-31.4.561. Retrieved 6 November 2011.
- Erwin, R. Michael; Truitt, Barry R.; Jiménez, Jaime E. (Spring 2001). "Ground-Nesting Waterbirds and Mammalian Carnivores in the Virginia Barrier Island Region: Running out of Options". Journal of Coastal Research (West Palm Beach, Florida: Coastal Education & Research Foundation, Inc.) 17 (2): 292–296. ISSN 0749-0208. Retrieved 16 November 2011.
- "Agreement Birds". Bonn, Germany: AEWA. 2006. Retrieved 1 November 2011.
Names and Taxonomy
Comments: Formerly (AOU 1983, 1998) included in the genus Sterna but separated on the basis of genetic data that correspond to plumage patterns (Bridge et al. 2005).