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.

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: R. t. tridactyla can be found on the Atlantic coast whereas R. t. pollicaris is found on the Pacific coast. 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.

Iceland

Kittiwakes are primarily pelagic piscivorous birds. Their main food source consists of fish, though it is not unlikely to find invertebrates such as copepods, polychete and squids in their diet, especially when fish is harder to find. Due to their wide range, kittiwake diet is quite variable. In the Gulf of Alaska, their diet is usually composed of Pacific capelin, Pacific herring, Pacific sand land and much more. Kittiwakes of the coast of the United Kingdom, in Europe, rely mostly on sandeels. In 2004, the kittiwake population in the Shetland islands, along with the murre (guillemot) and tern population, completely failed to reproduce successfully due to a collapse in sandeel stock. 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 focusing 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.

It is a coastal breeding bird around the north Pacific and north Atlantic oceans, found most commonly in North America and Europe. Kittiwakes are colonial nesters that form monogamous pairs and exhibit biparental care, meaning that both take part in nest building, incubation and chick rearing. They tend to nest in large numbers on cliffs by the sea side. It breeds in large colonies on cliffs and is very noisy on the breeding ground. Cliff nesting for gulls occurs only in the Rissa species, and the kittiwake is capable of utilizing the very sheerest of vertical cliffs, as is evident in their nesting sites on Staple Island in the outer Farne Islands. Black-legged kittiwake gulls traditionally preferred nesting on natural cliffs and ledges, and there are historically few instances of kittiwakes nesting on man-made structures. The first nesting on buildings on the River Tyne in Northumberland, England, began in 1949 at North Shields and then colonised further upstream, with nesting on buildings in central Newcastle upon Tyne and Gateshead from the early 1960s; 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, and usually ends in August. 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. Finally, the nest is lined with soft and dry material such as moss, grass or seaweed. The nest is solidified by a continuous trampling of the materials by the pair. Throughout this period, the male will do courtship feeding by feeding the female at their nest site. 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. ==== 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. The female will lay eggs on alternate days. The egg colour is variable, ranging from white, brownish to turquoise with dark brown speckles. Once the eggs are laid, the parents will take turns and incubate their clutch for an average period of 27 days. In case of egg loss, the female might relay another egg within 15 days after the loss. ==== Chick-rearing ==== Chicks usually hatch through the larger end of the egg using their egg tooth. The egg tooth usually disappears after seven days post-hatching. The alpha and beta chicks tend to hatch 1.3 days apart. Kittiwake are born semi-precocial. The downy young of kittiwakes are white, since they have no need of camouflage from predators, and do not wander from the nest like Larus gulls for obvious safety reasons. Regardless of predation, the chicks are most vulnerable within their first week due to their incapacity to properly thermoregulate during that period. Kittiwake chicks also exhibit siblicide, meaning that the first-born chick may kill its sibling in order to avoid competition for food from their paren…

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'.

==== Fisheries ==== Since the kittiwakes are fish specialist and tend to rely on prey species, their reproductive success highly depends on fish availability. Commercial fisheries have been known to have many direct and indirect impacts on their surrounding ecosystem. Direct impacts on the fish species themselves are well known, but the presence of fisheries also has an array of impacts on marine predators that not only rely on the species harvested but also on the "bycatch" species. 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. Long-term research on the effect of food availability on kittiwakes in the Gulf of Alaska showed a direct correlation between food availability and reproductive success, using a supplemental-feeding experiment. 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. Such effect on marine species can have tremendous impact on breeding kittiwakes which rely almost exclusively on pelagic fishes, making food more scarce in a time of high energetic needs.

There are still no global conservation plans for the black-legged kittiwake though the species is closely monitored for population trends shifts. There are currently no international legislations regarding this species. However, the black-legged kittiwake is protected under the Migratory Bird Treaty Act of 1918 that has been ratified by the US, Canada, Mexico, Russia and Japan. 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.

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'.