Common Tern
Encyclopedia
The Common Tern is a seabird
of the tern
family Sternidae. This bird
has a circumpolar distribution, breeding in temperate and sub-Arctic regions of Europe
, Asia
and east and central North America
. It is strongly migratory
, wintering in coastal tropical and subtropical regions. It is sometimes known as the sea swallow. Its foreign names are, in French: Sterne pierregarin; Spanish: Gaviotin comun (South America) or Charran comun; Portugese: Trinta-réis-boreal (Brazil) or Garajau-comun (Azores); German: Flusseeschwalbe. The old Scottish word for the Common Tern is pictar, occasionally encountered in Scotland
and the Maritime Provinces of Canada
.
. Its species' name is the Latin
hirundo, meaning "swallow". Four subspecies are generally recognized:
In North America, this species breeds along the Atlantic coast from Labrador to South Carolina, and inland throughout most of Canada east of the Rockies. In the United States, some breeding populations can also be found in the states bordering the Great Lakes, and on the Gulf Coast of Louisiana. These birds winter along the coasts of Central and South America, all the way down to Argentina on the east coast and to Northern Chile on the west coast.
(Sterna paradisaea), Roseate Tern
(S. dougalli), Antarctic Tern
(S. vittata), and South American Tern
(S. hirundinacea).
Breeding adults have light gray upperparts, white to very light gray underparts, a black cap, orange-red legs, and a thin, sharp, orange-red bill. The Common Tern's upperwings show a dark primary wedge, unlike the Arctic Tern in which the upperwing surface is uniformly grey. Its long tail extends no further than the folded wingtips on the standing bird, unlike Arctic and Roseate Terns in which the tail protrudes past the wingtips. The Common Tern is not as pale as the Roseate Tern and has longer wings. It is also smaller than the South American Tern.
In winter, the forehead and underparts are white, the bill is all black or black with a red base, and the legs are dark red or black.
Juvenile Common Terns show extensive ginger coloration and lack the 'scaly' appearance of juvenile Roseate Terns.
The Common tern forages up to 20 km away from the breeding colony, usually within 1 km of the shore. It seeks fish that are within about 50 cm of the surface, and huge foraging flocks can form at sea where predatory fish
drive prey fish to the surface. While bringing fish back to its nest it can be harassed by kleptoparasitic Jaegers
, Laughing Gulls, Roseate Terns, or by other Common Terns. It itself can attempt to steal fish from Arctic Terns or Least Terns.
Males select and start defending a nesting territory a few days after arrival in the spring. There a male is joined by his previous partner, unless she is more than 5 days late, in which case a divorce is likely. Aerial courtship displays then occur, in which a male and a female climb in wide circles to 100 m or more, or the male carries a fish in flight followed by several females, or birds descend together in zigzag glides. On the ground, males offer fishes to females. Once the pair is established or confirmed, both male and female scratch depressions in the ground, one of which will eventually become the nest. After the eggs are laid, some lining material is added throughout the incubation period, such as grass, reeds, or even rubbish.
Clutch size is normally three eggs, fewer in bad food years. Eggs are normally 42 × 30.5 mm, 20 ml, and 21 g. They are cream, buff, or brown, and finely marked with streaks or spots of black, brown or grey. Incubation is by both sexes and lasts 22–33 days, depending on disturbances at the colony which may leave the eggs unattended. On very hot days the incubating parent may fly to water to wet its belly feathers before returning to the eggs, thus affording the eggs some cooling. At hatching the young are precocial, eyes open, covered in thick down, and capable of standing and taking food within 1–3 h. Young are brooded and fed fishes by both sexes. Chicks remain on nesting territory, forsaking the nest but seeking refuge in vegetation. They fledge after 22–29 days.
Like many terns, this species is very defensive of its nest and young and will harass humans, dogs, muskrats and most diurnal birds, but unlike the more aggressive Arctic Tern
it rarely hits the intruder, usually swerving off at the last moment. Adults can discriminate between individual humans, attacking familiar people more intensely than strangers. Nocturnal predators do not elicit similar attacks; colonies can be wiped out by rats, and adults desert the colony for up to 8 h when Great-Horned Owls are present.
Common terns usually breed once a year. Second clutches are possible if the first one is lost. Rarely, a second clutch may be laid and incubated while some chicks from the first clutch are still being fed. First breeding attempt is usually at 4 years of age, sometimes at 3 years. Maximum documented lifespan in the wild is 26 years.
and Short-Eared Owls
can take adults and chicks, while Black-crowned Night Herons
can take small chicks. Peregrine falcons can kill adults. A more surprising predator is the Ruddy Turnstone
, which can take eggs in unattended nests.
On land it can walk or run. It perches on rocks, posts, rails, boats, or buoys.
and sunbathing have not been reported. Water bathing is done in shallow waters close to shore. Sleep is done with the bill tucked into the scapular (shoulder) feathers.
trade, where feathers, wings, and sometimes whole stuffed birds were used as hat decorations. Conservation initiatives greatly eased such pressures and the species recovered in the first half of the 20th century. However, starting in the mid-20th century, populations have started to decline again, likely due to a combination of factors such as competition for nesting sites by gulls (whose populations blossomed near garbage dumps), disturbance by people and off-road vehicles, and storm floods. The Common Tern is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds and the U.S.-Canada Migratory Bird Treaty apply.
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
of the tern
Tern
Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...
family Sternidae. This bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
has a circumpolar distribution, breeding in temperate and sub-Arctic regions of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and east and central North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. It is strongly migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
, wintering in coastal tropical and subtropical regions. It is sometimes known as the sea swallow. Its foreign names are, in French: Sterne pierregarin; Spanish: Gaviotin comun (South America) or Charran comun; Portugese: Trinta-réis-boreal (Brazil) or Garajau-comun (Azores); German: Flusseeschwalbe. The old Scottish word for the Common Tern is pictar, occasionally encountered in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
and the Maritime Provinces of Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
.
Taxonomy, systematics, and distribution
The Common Tern was one of the many species first described by Linnaeus in his 1758 work Systema NaturaeSystema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...
. Its species' name is the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
hirundo, meaning "swallow". Four subspecies are generally recognized:
- S. h. hirundo described by Linnaeus, is found in Americas, Europe, Africa, and Middle East.
- S. h. minussensis described by Sushkin in 1925, breeds in central Asia to Southern Tibet, winters mainly in Indian Ocean.
- S. h. longipennis described by Nordmann in 1835, breeds north of tibetana and winters from South East Asia to Australia.
- S. h. tibetana described by Saunders in 1876, breeds in high altitude lakes south and east of minussensiss range to Sichuan, winters in Indian Ocean.
In North America, this species breeds along the Atlantic coast from Labrador to South Carolina, and inland throughout most of Canada east of the Rockies. In the United States, some breeding populations can also be found in the states bordering the Great Lakes, and on the Gulf Coast of Louisiana. These birds winter along the coasts of Central and South America, all the way down to Argentina on the east coast and to Northern Chile on the west coast.
Description
This medium-sized tern is 32–39 cm long (including a 6-9 cm fork in the tail) with a 72–83 cm wingspan. It weighs 97-146 g. It is most readily confused within its range with the similar Arctic TernArctic Tern
The Arctic Tern is a seabird of the tern family Sternidae. This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe, Asia, and North America...
(Sterna paradisaea), Roseate Tern
Roseate Tern
The Roseate Tern is a seabird of the tern family Sternidae. This bird has a number of geographical races, differing mainly in bill colour and minor plumage details....
(S. dougalli), Antarctic Tern
Antarctic Tern
The Antarctic Tern is a typical tern. It ranges throughout the southern oceans. It is very similar in appearance to the closely related Arctic Tern, but is stockier, and the wing tips are grey instead of blackish in flight...
(S. vittata), and South American Tern
South American Tern
The South American Tern is a species of tern found in coastal regions of southern South America, including the Falkland Islands, ranging north to Peru and Brazil . It is generally the commonest tern in its range. It closely resembles the smaller, highly migratory Common Tern.-References:*...
(S. hirundinacea).
Breeding adults have light gray upperparts, white to very light gray underparts, a black cap, orange-red legs, and a thin, sharp, orange-red bill. The Common Tern's upperwings show a dark primary wedge, unlike the Arctic Tern in which the upperwing surface is uniformly grey. Its long tail extends no further than the folded wingtips on the standing bird, unlike Arctic and Roseate Terns in which the tail protrudes past the wingtips. The Common Tern is not as pale as the Roseate Tern and has longer wings. It is also smaller than the South American Tern.
In winter, the forehead and underparts are white, the bill is all black or black with a red base, and the legs are dark red or black.
Juvenile Common Terns show extensive ginger coloration and lack the 'scaly' appearance of juvenile Roseate Terns.
Habitat
This species breeds close to freshwater or seawater, in habitats such as sandy barrier beaches, vegetated sandy dune areas, or (most commonly) islands. It can adapt to artificial nesting structures. Outside of the breeding season, these birds are found on coastal estuaries or along large rivers. They can be seen in harbours and on jetties and piers.Food and feeding
Like all Sterna terns, the Common Tern feeds by plunge-diving for fish, from a height of 1-6 m, either in the sea or in freshwater lakes and large rivers. It usually dives directly, and not from the "stepped-hover" favoured by Arctic Tern. It commonly forages in flocks (though in inland populations, individuals often forage singly on in pairs). The prey fish are 5-15 cm long. Occasionally it can also take insects, crustaceans, and dead fish.The Common tern forages up to 20 km away from the breeding colony, usually within 1 km of the shore. It seeks fish that are within about 50 cm of the surface, and huge foraging flocks can form at sea where predatory fish
Predatory fish
Predatory fish are fish that predate upon other fish or animals. Some predatory fish include perch, muskie , pike, walleye, salmon.Levels of large predatory fish in the global oceans are estimated to be about 10% of their pre-industrial levels...
drive prey fish to the surface. While bringing fish back to its nest it can be harassed by kleptoparasitic Jaegers
Skua
The skuas are a group of seabirds with about seven species forming the family Stercorariidae and the genus Stercorarius. The three smaller skuas are called jaegers in North America....
, Laughing Gulls, Roseate Terns, or by other Common Terns. It itself can attempt to steal fish from Arctic Terns or Least Terns.
Breeding
This species breeds in colonies with as few as 20 pairs and as many as 6000, on coasts and islands, or inland on suitable freshwater lakes. It prefers sites with some vegetation that will afford cover to the newly hatched chicks. When natural sites are not available, it has been known to establish colonies on dredge spoil islands, derelict piers and barges, breakwaters, and floating rafts (including rafts created as part of restoration efforts for tern colonies).Males select and start defending a nesting territory a few days after arrival in the spring. There a male is joined by his previous partner, unless she is more than 5 days late, in which case a divorce is likely. Aerial courtship displays then occur, in which a male and a female climb in wide circles to 100 m or more, or the male carries a fish in flight followed by several females, or birds descend together in zigzag glides. On the ground, males offer fishes to females. Once the pair is established or confirmed, both male and female scratch depressions in the ground, one of which will eventually become the nest. After the eggs are laid, some lining material is added throughout the incubation period, such as grass, reeds, or even rubbish.
Clutch size is normally three eggs, fewer in bad food years. Eggs are normally 42 × 30.5 mm, 20 ml, and 21 g. They are cream, buff, or brown, and finely marked with streaks or spots of black, brown or grey. Incubation is by both sexes and lasts 22–33 days, depending on disturbances at the colony which may leave the eggs unattended. On very hot days the incubating parent may fly to water to wet its belly feathers before returning to the eggs, thus affording the eggs some cooling. At hatching the young are precocial, eyes open, covered in thick down, and capable of standing and taking food within 1–3 h. Young are brooded and fed fishes by both sexes. Chicks remain on nesting territory, forsaking the nest but seeking refuge in vegetation. They fledge after 22–29 days.
Like many terns, this species is very defensive of its nest and young and will harass humans, dogs, muskrats and most diurnal birds, but unlike the more aggressive Arctic Tern
Arctic Tern
The Arctic Tern is a seabird of the tern family Sternidae. This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe, Asia, and North America...
it rarely hits the intruder, usually swerving off at the last moment. Adults can discriminate between individual humans, attacking familiar people more intensely than strangers. Nocturnal predators do not elicit similar attacks; colonies can be wiped out by rats, and adults desert the colony for up to 8 h when Great-Horned Owls are present.
Common terns usually breed once a year. Second clutches are possible if the first one is lost. Rarely, a second clutch may be laid and incubated while some chicks from the first clutch are still being fed. First breeding attempt is usually at 4 years of age, sometimes at 3 years. Maximum documented lifespan in the wild is 26 years.
Sounds
Many calls exist and all have a sharp irritable timbre, and a lower pitch than the equivalent calls in Arctic Terns. The most common calls are a kip uttered during social contact, a down-slurred keeur given when approaching the colony while carrying a fish and possibly used for individual recognition (chicks emerge from hiding when they hear their parents giving this call), and a shrill kee-arr given when alarmed. There are other calls associated with fear, attack, brooding, begging, and mating.Predators
Eggs are vulnerable to rats, who can even store large number of eggs in caches. Weasels can also take chicks. However, the habit of Common Terns to nest on islands means that the most common predators are other birds rather than mammals. Gulls can take chicks. Great Horned OwlsGreat Horned Owl
The Great Horned Owl, , also known as the Tiger Owl, is a large owl native to the Americas. It is an adaptable bird with a vast range and is the most widely distributed true owl in the Americas.-Description:...
and Short-Eared Owls
Short-eared Owl
The Short-eared Owl is a species of typical owl . In Scotland this species of owl is often referred to as a cataface, grass owl or short-horned hootlet. Owls belonging to genus Asio are known as the eared owls, as they have tufts of feathers resembling mammalian ears. These "ear" tufts may or may...
can take adults and chicks, while Black-crowned Night Herons
Black-crowned Night Heron
The Black-crowned Night Heron commonly abbreviated to just Night Heron in Eurasia, is a medium-sized heron found throughout a large part of the world, except in the coldest regions and Australasia .-Description:Adults are...
can take small chicks. Peregrine falcons can kill adults. A more surprising predator is the Ruddy Turnstone
Ruddy Turnstone
The Ruddy Turnstone is a small wading bird, one of two species of turnstone in the genus Arenaria. It is now classified in the sandpiper family Scolopacidae but was formerly sometimes placed in the plover family Charadriidae...
, which can take eggs in unattended nests.
Locomotion
The Common tern is an agile flyer, capable of rapid turns and swoops, hovering, and vertical take-off. Flight speed during migration is 12-15 m/s (43-54 km/h, or 27-33 mph).. When commuting with fish it flies close to the surface in a strong head wind, but 10-30 m above the surface otherwise.On land it can walk or run. It perches on rocks, posts, rails, boats, or buoys.
Self-maintenance
Head-scratching with the foot is direct (not over the wing) and can be performed during flight. AntingAnting (bird activity)
In the behavior called anting, birds rub insects on their feathers, usually ants, which secrete liquids containing chemicals such as formic acid, that can act as an insecticide, miticide, fungicide, bactericide, or to make them edible by removing the distasteful acid. It possibly also supplements...
and sunbathing have not been reported. Water bathing is done in shallow waters close to shore. Sleep is done with the bill tucked into the scapular (shoulder) feathers.
Relationship with humans
Populations of Common terns were greatly reduced in the 19th century because of habitat loss due to development, hunting and egging by people, and also because of the millineryMillinery
Hatmaking is the manufacture of hats and headwear, millinery is the designing and manufacture of ladies’ hats.-Notable hatters:* Gerard Albouy , often known by the name Ouy, a French milliner...
trade, where feathers, wings, and sometimes whole stuffed birds were used as hat decorations. Conservation initiatives greatly eased such pressures and the species recovered in the first half of the 20th century. However, starting in the mid-20th century, populations have started to decline again, likely due to a combination of factors such as competition for nesting sites by gulls (whose populations blossomed near garbage dumps), disturbance by people and off-road vehicles, and storm floods. The Common Tern is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds and the U.S.-Canada Migratory Bird Treaty apply.
External links
- Common Tern videos, photos & sounds on the Internet Bird Collection
- Common Tern Species Account - Cornell Lab of Ornithology
- Common Tern - Sterna hirundo - USGS Patuxent Bird Identification InfoCenter
- Common Tern Information and Photos - South Dakota Birds and Birding
- Common Tern Profile - Madeira Wind Birds