Sandwich terns are migratory seabirds that breed at large nesting colonies along the warm-water coasts of Europe, parts of the south-eastern United States, the Caribbean and as far south as Patagonia in South America. Their distinctive yellow-tipped bill and shaggy black crest make them relatively unmistakable alongside similar seabird species.
Sandwich Tern adult in winter plumage
Juvenile Sandwich Tern
Sandwich Tern portrait
Sandwich Tern in-flight in winter plumage
Family:Gulls and terns
36cm to 41cm
95cm to 105cm
210g to 260g
In breeding plumage, Sandwich terns have a bold black crown that extends across the entire top of the head, ending in a spiky crest. Their upperparts are light grey, while their underparts are bright white.
The bill is mainly black, although at close range a bright yellow tip is visible, which distinguishes the Sandwich tern from other tern species that are found in North America. Legs are black in both males and females.
Visually there is no difference between male and female Sandwich terns. Research shows that females have a shorter combined measurement of head and beak, and males have longer lower legs and toes than females.
After eggs are laid, the transition to winter plumage begins, with the black crown gradually being replaced by a white forehead.
Sandwich terns have rugged crowns, which are similar in appearance to the receding white and dusky grey seen in non-breeding adults. Their backs are heavily marked with grey and black, and their wings are barred with dusky grey. Bills of juvenile Sandwich terns are shorter and wider than those of adults and do not always have the yellow tip.
Sandwich Tern adult in breeding plumage
Male and female sandwich terns exhibit some small differences in size and body structure, with males having longer legs and toes, as well as longer combined head and bill measurements.
Pair of Sandwich Terns engaged in courtship
A shrill ‘kerrr-ick’ call is used by Sandwich terns for advertising territory ahead of the breeding season, as well as serving as a contact call. A cackling ‘gagaga’ cry is commonly heard from birds on the nest when intruders approach and may also be heard when they are defending foraging grounds.
Sandwich Tern crying out
Small fish, such as whiting, herring, anchovy, sprats, and sand eels are among the primary foods eaten by Sandwich terns, caught during plunging dives beneath the surface of the sea. Squid and crustaceans and occasional insects are also eaten.
Until they are able to handle larger prey items, Sandwich tern chicks are fed on regurgitated fish by their parents, including menhaden, shrimps, herring, and bluefish. Parents continue to feed their young for up to four months.
Sandwich Tern catching small fish
Sandwich terns are a coastal species, rarely found inland, and nesting colonially at low-lying sandy, muddy, or gravelly beaches.
Outside the breeding season, mangroves, estuaries, and harbours are commonly visited by Sandwich terns for feeding and roosting. Warm-water coastal areas are preferred, although in parts of Central America, freshwater lakes and salt marshes may also attract overwintering birds.
In Europe, Sandwich terns breed in four distinct regions but generally leave the continent for West African wintering grounds each autumn.
In northern Europe, the species breeds along the coasts of the British Isles, the south coast of Norway, France, the Netherlands, Denmark, the south coast of Norway, and Germany.
In southern Europe and North Africa, Sandwich terns can be seen during spring and summer at colonies along the Mediterranean Sea in Spain, southern France, Sardinia, Sicily, Italy, and south-eastern Tunisia. Also, populations of Sandwich terns breed on the islands of the Black Sea and along the eastern and southern coasts of the Caspian Sea.
In North America, breeding populations of Sandwich terns are found along the Atlantic coast from Virginia to South Carolina, and along the Gulf Coast, from Florida to Texas. Caribbean populations are mainly concentrated in the West Indies, in Cuba, and in Puerto Rico.
In South America, Sandwich tern colonies are found in Venezuela, Brazil and Argentina.
In Europe, where the species’ total population is thought to be between 80,000 and 148,000 pairs, the Netherlands, the UK, and Germany have the largest breeding populations, each with more than 10,000 pairs nesting annually.
Up to 46,945 pairs breed in the US, with a further 8,000 pairs in the Caribbean. Brazil has around 16,000 nesting pairs, and in Argentina, there are estimated to be a further 10,000, although data from South America is hard to verify.
Sandwich Terns standing on rocks by the sea
The global population of Sandwich terns has an upper estimate of 640,000 individuals, although worldwide, the species tends to be concentrated at large breeding colonies rather than distributed evenly across their range. This may give the impression that they are a rare species, as they are not particularly widespread.
The United States is home to an estimated 25 to 32 percent of the global population of Sandwich terns, with up to 46,945 breeding pairs.
The vast majority of these – between 59 and 77 percent – can be found along the Louisiana coast, with a notable colony with more than 20,000 pairs found on the Chandeleur Islands.
Breeding colonies of sandwich terns are scattered along the coastline of eastern and southern England, east and west Scotland, the Isle of Man, and parts of north Wales.
Nature reserves at Minsmere in Suffolk, Dungeness in Kent, and on the north Norfolk coast have sizeable breeding colonies where sightings are usually fairly common during spring and summer.
Colony of Sandwich Terns
The average lifespan of a Sandwich tern is around 12 years, with breeding occurring for the first time at three years. However, occasionally much older birds are identified, including a ringed individual of 30 years and 9 months in 1998.
Gulls are the chief predator of Sandwich terns’ eggs and young, while stoats are also frequently observed to raid nests.
Arctic foxes are common predators among Sandwich tern nest colonies, preying on adult birds and occasionally leading to an entire colony being destroyed. Peregrine falcons also hunt adult terns in their shoreline habitats.
The Wildlife and Countryside Act, of 1981, protects Sandwich terns in the UK against being deliberately killed, injured, or taken into captivity. The species is also listed in the Birds Directive Annex 1, EU legislation for the conservation of wild birds across Europe.
In the UK, Sandwich terns are rated as an Amber status species on the British Birds of Conservation Concern list. Globally, they are considered a species of least concern, with between 490,000 and 640,000 individuals.
Disturbance of nesting colonies by humans is a leading threat worldwide, particularly in their South American breeding grounds, where less than half of nesting areas are protected.
Sandwich Tern in flight with a sea eel in its beak
Sandwich terns nest on coastal beaches and barrier islands, finding sandy or earthy spots directly on the shore and hollowing out a shallow depression on flat, open ground.
Large-scale colonial nesting is usual, with between 100 and 4,000 pairs. Nests are placed in close proximity to one another, as near as 20 cm to 30 cm (8 in to 12 in) apart.
Nests are at risk of being washed away by the tide, and in order to add an extra layer of protection, they often defecate around the rim of their nest scrape, with their droppings solidifying into a protective ‘ring’ which then has a greater chance of withstanding heavy rain or flooding.
Regardless of their location, sandwich terns breed in spring and summer, so in the northern hemisphere, the peak laying months are from April to June, while in their southern hemisphere breeding grounds, e.g. in Patagonia, breeding takes place in October.
Pairs raise a single brood together before going their separate ways ahead of their autumn migrations.
Sandwich tern eggs vary in colour from pure white to a darker pinkish-buff. Surface markings also vary, from slight dark speckling to heavier scrawls that cover the entire egg.
A typical clutch contains either one or two eggs, which measure 51 mm by 36 mm (2 in by 1.4 in), and incubation is shared equally between the male and female for between 21 and 29 days (on average 23 to 25 days).
Pairs are believed to form during spring migration, and sandwich terns arrive on their breeding grounds with a mate.
Pair bonds normally last for the duration of a single breeding season and do not last through the winter, with a new mate usually being selected the following year, although occasionally pairs that have previously bred together will reunite.
While pairs are thought to be monogamous, reports do exist of males mating with more than one female away from their main nest site.
Pair of Sandwich Terns during the breeding season
Sandwich terns are notably less aggressive than fellow tern species such as the common tern, and tolerate approaches to their nests without becoming physically confrontational.
Some vocal threat calls may be heard, including a ‘gackering’ cry, but posturing and head bobbing is usually as aggressive as it gets before the Sandwich tern backs off.
It’s common for Sandwich terns to nest among more aggressive species, including Arctic terns, laughing gulls, black-headed gulls, and royal terns, to avoid predation from larger avian predators.
Sandwich terns sleep and roost facing into the wind, usually on the shore of a beach close to the tide line.
Pair of Sandwich Terns on the beach having a disagreement
Sandwich terns are generally migratory, with European breeding populations departing each autumn for wintering grounds along the coast of West Africa, on a migration journey of more than 4,000 km (2,500 mi).
Around 65 individuals do remain in the UK during winter months, but these are an exception.
In the US, the coast of Florida and the Gulf of Mexico are important winter destinations, with some populations heading further afield, into Mexico and Central America. In the Caribbean and parts of South America, many Sandwich tern populations are resident all year round.
Sandwich Tern in-flight with prey in its beak
Sandwich terns are named after the town of Sandwich on the Kent coast, in southeast England.
Common terns have a bill that is mainly orange-red with a black tip, in contrast to the black, yellow-tipped bill of the Sandwich tern.
Common terns are also slightly smaller than Sandwich terns, and although they have a smaller overall UK population, they are more widely distributed.
Named in honour of the French naturalist and ornithologist, Jean Victor Audouin (1797 – 1841) the Audouin’s gull is one of the world’s rarest and is limited in the main to regions within and surrounding the Mediterranean Sea.
Until fairly recently yellow-legged gulls were considered a subspecies of the caspian gull or the herring gull. In 2007, the British Ornithologists’ Union first listed it as a distinct species with key differences in appearance and distribution range from similar-looking gulls.
Roseate terns have a wide distribution range, and are found on six continents around the world. However, numbers have declined dramatically in some regions, leading to conservation concerns over the long-term survival of the species.
Despite its name, the Mediterranean gull is not limited to coastal waters of southern Europe, and is widespread on the Atlantic and Black Sea coasts, as well as in coastal regions and inland reservoirs of England and Wales.
A tiny, but feisty, seabird, the little tern undertakes epic annual migrations of up to 10,000 km (6,000 miles) between breeding grounds along the UK coast to winter territories in West Africa. Further east, little tern populations complete similar journeys from China and Japan to Australia each year.
Little gulls are small, tern-sized seabirds that breed mainly in Central Asia, but are occasionally reported as vagrant breeders in North America and may be seen in passage around coastal areas of the UK, and rarely reach the United States and Canada.
Lesser Black-Backed Gull
The Lesser Black-backed Gull is one of many attractive ‘white-headed-gulls’ from the Larus genus. Common in the UK throughout the year, these migratory seabirds also visit the eastern half of the United States each winter.
The Kittiwake is an attractive, short-legged gull that breeds on rocky cliffs along the UK’s coastline. These birds disperse each winter to forage out over the open ocean.
Iceland Gulls breed exclusively along the rocky coastlines of north-east Canada to Greenland. Winter migration south occurs, with temporary visitors arriving along both Atlantic and Pacific coasts of the United States, and to coastal areas across north-western Europe.
A familiar bird of the coast, the bold and long-lived Herring Gull is a fascinating seabird in decline.
Great Black-Backed Gull
The Great Black-backed Gull is the world’s largest gull and one formidable seabird. This impressive species lives and breeds along Northern Hemisphere shores on both sides of the Atlantic.
A large, pale gull species, the Glaucous gull breeds across the Arctic, where it hunts for fish, birds and small mammals and scavenges for carrion. Known for their intolerance of sharing a food source with other birds, Glaucous gulls can be physically aggressive as well as highly vocal when approached.
Terns are water birds from the family Sternidae and are expert fish catchers. There are generally considered to be forty five separate species of terns worldwide. Generally smaller than gulls but with long tails, thin bodies and short legs, they are long distance migrants.
There are four sub-species of the common gull with the European variant being the nominate. The other three are the Russian, Kamchatka and American, which are all predominantly confined to the geographical region attributed by their name. There are subtle differences in plumage and overall size of bird between sub-species.
The title of Black-headed Gull is rather a misnomer for this bird as its head is not black but a dark brown colour and only in adult birds during the breeding season. It is not present during the winter months or in other plumages. Unlike many gulls it is not restricted to coastal regions and is widespread inland in both rural and urban areas.
The Black Tern is a small, graceful seabird that nests far from the ocean. These birds switch between radically different habitats in the breeding and non-breeding seasons, but habitat loss inland has caused their numbers to plummet since the mid-1900s.
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