Black-legged kittiwake

The black-legged kittiwake (Rissa tridactyla) is a seabird species in the gull family Laridae. This species was first described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae as Larus tridactylus. The English name is derived from its call, a shrill 'kittee-wa-aaake, kitte-wa-aaake'. In North America, this species is known as the black-legged kittiwake to differentiate it from the red-legged kittiwake, but in Europe, where it is the only member of the genus, it is often known just as kittiwake.

Taxonomy

The black-legged kittiwake was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae. He placed with the gulls in the genus Larus and coined the binomial name Larus tridactylus. Linnaeus specified the type location as northern Europe but this has been restricted to Great Britain. The black-legged kittiwake is now placed together with the red-legged kittiwake in the genus Rissa that was introduced in 1826 by the English naturalist James Stephens. The genus name is from the Icelandic word "rita" for a black-legged kittiwake. The specific tridactyla is from Ancient Greek tridaktulos meaning "three-toed". The English name "kittiwake" is derived from its call, a shrill 'kittee-wa-aaake, kitte-wa-aaake'.

Subspecies

Two subspecies are recognised. These are listed below together with their breeding ranges. It can be found all across the northern coasts of the Atlantic, from Canada to Greenland as well as on the Pacific side from Alaska to the coast of Siberia. Black-legged kittiwakes' wintering range extends further south from the St-Lawrence to the southern coast of New Jersey as well as in China, the Sargasso sea and off the coast of west Africa. There are two subspecies of black-legged kittiwake. Rissa tridactyla tridactyla can be found on the Atlantic coast whereas Rissa tridactyla pollicaris is found on the Pacific coast.

thumb|A vagrant kittiwake at [[Borith Lake, high in the Karakoram mountains of northern Pakistan, over 1,400 km from the Indian Ocean and over 5,000 km overland from the nearest breeding colonies]]

Out of all the gulls, the kittiwakes are the most pelagic ones, except for perhaps Sabine's gull. Kittiwakes are almost exclusively found at sea with the exception of the breeding period, from May to September, where they can be found nesting on the sheerest sea cliffs. They are rarely found inland, though occasional vagrants can turn up far inland, even in central Asia well over a thousand km from the sea. For the rest of the year, kittiwake spend most of their time on the wing out of sight from the coast.

Description

Adult plumage

The adult is in length with a wingspan of and a body mass of . Studies show that integument colour is associated with male's reproductive success. As their Latin name suggests, they only possess three toes since their hind toe is either extremely reduced or completely absent.

Juvenile plumage

At fledging, the juveniles differ from the adults in having a black 'W' band across the length of the wings and whiter secondary and primary feathers behind the black 'W', a black hind-neck collar and a black terminal band on the tail. Kittiwakes obtain their mature plumage at 4 years old, but will gradually change their juvenile plumage over time until maturity is reached. A second-year juvenile resembles a hatch-year regarding the plumage, though the bill is no longer solid black but instead has a greenish colour. The head of the red-legged kittiwake is slightly smaller and bears a shorter bill. by 2020, 1,639 pairs were nesting on buildings along the Tyne (of which 879 pairs on the iconic Tyne Bridge in the heart of Newcastle), with the furthest inland 17 km upriver from the sea. In recent years, some have even been nesting successfully on top of street lights on Newcastle's Quayside. A shift in nesting behaviour has also been noted in the coastal areas of Northern Norway.

Nesting

Kittiwake pairs both participate in building the nest in which the female will lay their eggs. The breeding season begins with nest refurbishment in late March or early April, and egg-laying from late April, Building the nest in order to welcome their fragile eggs is a tedious task and requires time and energy. The parents begin with a layer of mud and grass in order to form a platform that will cushion and help to isolate the eggs from the cold ground. A cup is then built around the platform in order to keep the eggs from rolling out of the nest. The reasons for such behaviour are not quite understood but many hypotheses have been brought up to explain the phenomenon. Hypothesis such as the "nutrition hypothesis" and the "copulation enhancement hypothesis" have shown evidence that this behaviour evolved either through natural or sexual selection.

Black-legged Kittiwake and Chick.jpg|On nest with chick

Dreizehenmöwe.jpg|Adult and chicks

Black-legged kittiwakes (Rissa tridactyla) immatures on nests Keflavíkurbjarg cliffs.jpg|immatures on nests<br />Keflavíkurbjarg cliffs, Iceland

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Eggs and incubation

thumb|Eggs, Collection [[Museum Wiesbaden]]

Kittiwakes are single-brooded, meaning that the pair will only reproduce once per year. Egg formation within the female usually takes around 15 days and normal egg clutch size ranges from one to two sub-elliptical eggs, though three eggs clutches are not impossible. In case of egg loss, the female might relay another egg within 15 days after the loss. The egg tooth usually disappear after seven days post-hatching. Chicks will come back to the nest for several weeks after hatching and will eventually follow the adults at sea where they spend the winter. In 2004, the kittiwake population in the Shetland islands, along with the murre (guillemot) and tern Like most gulls, kittiwake forage at the surface of the water where they tend to catch their prey while in flight or sitting on the water. Throughout winter, kittiwakes spend all of their time at sea where they forage. Unlike some gull species, they do not scavenge at landfills. Fisheries harvesting species such as the sandeel, one of the main food source for kittiwakes in Europe, are known to have a huge impact of the reproductive success of local populations kittiwakes and other seabirds. Seabirds can also be a direct victim of fisheries. Their tendency to hang around them in hope of a good meal can lead to entanglements in fishing gear, often resulting in death by drowning.

Global warming

With global warming, the rising of ocean temperature is becoming a serious concern, affecting not only the marine flora and fauna but also the species exploiting the marine environment. Kittiwake are extremely sensitive to variation in food stocks. Such variations can be due to over exploitation, as mentioned above, but can also be due to variations in sea surface temperature. With the rising the sea surface temperature, many fishes, such as sandeels, are negatively affected by a rise in ocean temperature. Studies show that sandeels and many copepods populations are being negatively impacted due to increasing sea surface temperature. As for many gull species, the kittiwake is not a species of special interest for the public, therefore there are no education plans put in place in order to inform and educate people regarding this species.

Gallery

File:Black-legged-Kittiwake.jpg|In flight, Heligoland, Germany

File:Black-legged Kittiwake RWD2.jpg|In Seward, Alaska

File:Rissa tridactyla standing.jpg|

File:Black-legged Kittiwake.jpg|Colony at Svalbard

File:arcticskua.jpg|Chased by a parasitic jaeger at Svalbard

File:Dreizehenmoewen.jpg|At the Norwegian bird-island Runde

File:Dreizehenmoewenpaar.jpg|At Runde

File:Rissa tridactyla-pjt.jpg|Youth (Iceland)

File:Black-legged Kittiwake from the Crossley ID Guide Britain and Ireland.jpg|ID composite

File:Capfagnet 21.jpg|Capture of individuals for tagging

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References

External links

Black-legged kittiwake - Rissa tridactyla - USGS Patuxent Bird Identification InfoCenter