Black-legged kittiwake

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. • R. t. tridactyla (Linnaeus, 1758): North Atlantic Ocean, from high Arctic to temperate coasts, in Greenland, Iceland, west and northwest Europe, Svalbard and northwest New Siberian Islands, the Canadian high Arctic (northeast Canada), Gulf of St. Lawrence and Newfoundland (southeast Canada). Unique among the Laridae in having only a very small or even no hind toe. • R. t. pollicaris Ridgway, 1884: North Pacific Ocean, from high Arctic to temperate north coasts, from the northeast New Siberian Islands to Sakhalin, Kamchatka Peninsula, Kuril and Commander Islands (east Russia), the Aleutian Islands and Bering Sea islands, and west and southwest Alaska mainland. Hind toe (as the name pollex, meaning thumb, suggests) present. Apart from the hind toe, the two subspecies are almost identical, R. tridactyla pollicaris is in general slightly larger than R. tridactyla tridactyla. ==Distribution and habitat==

The black-legged kittiwake is a coastal bird of the arctic to subarctic regions of the world. 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. , 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. The chicks of the Pacific black-legged kittiwake and red-legged kittiwake cannot be distinguished during their youngest downy phase. Juvenile black-legged kittiwakes can be confused with juvenile little gull and both juvenile and adult Sabine's gull, although the kittiwakes' plumage has broader black 'W' on the wing, the primaries and a different pattern going across the coverts. ==Behaviour and ecology==

Flight Kittiwake are known for their graceful flight. Unlike larger gulls, their flight is light with the wings beating in fast strokes. 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 nestsKeflavíkurbjarg cliffs, Iceland Eggs and incubation 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. The foraging style of the kittiwakes is often compared to the terns' foraging strategy due to their frequent hovering and their head diving quickly at the surface of the water. Instances of kittiwakes following whales are also common since they benefit from the fish fragments expelled by these huge marine mammals. Fishers and commercial fishing boats are also the frequent witnesses of big groups of kittiwakes, often mixed with other gull species and terns, hovering around their ship in order to benefit from the scraps rejected in their sewage water or thrown overboard. There are few studies focussing on their water needs, though they seem to prefer salt water to fresh water. Captive kittiwakes are known to refuse fresh water but will willingly drink salt water. == Relationship with humans ==

Kittiwakes are a frequent encounter of fisheries in northern regions. Their diet consisting almost exclusively of fish, fishermen tend to seek large aggregation of seabirds since they are often a sign of fish abundance. On the other hand, kittiwake and other seabirds hang around fishing boats or platforms to collect scraps or any fish that might have been left out. Due to the pelagic lifestyle of kittiwakes, they rarely interact with humans on the land, other than occasional sight near the ocean's coast. In New England, the black-legged kittiwake is often called the "winter gull" since its arrival often signals to people that winter is coming. The city of Tromsø, along with other cities in the far north of Norway, has experienced a remarkable increase in the number of kittiwakes choosing to use city structures as nesting sites. This rise in urban nesting populations has seen the number of pairs increase from 13 in 2017 to over 380 in 2022. Researchers attribute this climate change related breeding failures, along with the absence of natural predators in the city, providing a safer environment for the gulls to breed and raise their young. The increasing nesting population has created challenges, as the gulls produce ammonia-smelling faeces, discolouring buildings and streets, as well as the noise pollution generated by their constant 'kittiwake' calling. To address these challenges, innovative measures have been implemented in Tromsø. One such initiative involves the establishment of "Kittiwake hotels", artificial bird cliff structures built to encourage nesting away from urban facades. The hotels have, along with mitigation measures preventing nesting on the city's structures, had success in attracting kittiwakes without having a negative impact on breeding. == Conservation ==

Population trends Since the 1970s, it has been believed that the global population of black-legged kittiwake has declined of about 40% in only three generations (one generation is in average 12.9 years), putting the species in a dangerous place for the future. 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 ==References==