Black-Legged Kittiwake Overview and Population Trends

The Black-Legged Kittiwake is a fascinating bird species found in the North Atlantic. They are medium-sized gulls with a distinctive black band across their legs.

One of the most notable features of the Black-Legged Kittiwake is their ability to adapt to different environments. They thrive in coastal areas, often nesting on cliffs and rocky shores.

Black-Legged Kittiwakes are known for their unique breeding habits, with pairs forming in the fall and staying together for several years. This monogamous behavior is a key factor in their successful breeding and population growth.

Their population has been declining in recent years, with a significant drop in numbers between 1993 and 2005.

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The Black-legged Kittiwake is a striking bird with some unique physical characteristics. It measures 37-41 cm in length and has a wingspan of 91-105 cm.

One of the most distinctive features of the Black-legged Kittiwake is its bright yellow bill. The inside of their mouth is also a characteristic feature of the species due to its rich red colour.

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The species has a white head and body, with a grey back and grey wings tipped solid black. Black legs are a common feature, although some individuals may have pinky-grey to reddish legs.

In winter, the Black-legged Kittiwake acquires a dark grey smudge behind the eye and a grey hind-neck collar. The bill also turns a dusky-olive colour during this time.

The Black-legged Kittiwake has a unique foot structure, with only three toes, as their hind toe is either extremely reduced or completely absent.

The black-legged kittiwake is a bird of the arctic to subarctic regions, found all across the northern coasts of the Atlantic and Pacific.

They can be found on the Atlantic coast from Canada to Greenland, and on the Pacific side from Alaska to the coast of Siberia. In fact, their 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, found on the Atlantic coast, and Rissa tridactyla pollicaris, found on the Pacific coast.

Black-legged kittiwakes are almost exclusively found at sea, except for the breeding period from May to September, where they can be found nesting on sheer sea cliffs. They rarely venture inland, but occasional vagrants can turn up far inland, even in central Asia over a thousand km from the sea.

Here's a breakdown of the gull families, just for reference:

Black-legged kittiwakes spend most of their time at sea, gathering in areas of upwellings, sometimes over the edge of the continental shelf. They can be found from the coast to over a hundred miles offshore, making them a common sight for sailors and coastal residents.

The black-legged kittiwake is a fascinating bird species that's well adapted to its coastal habitat. They breed in large colonies, often mixed with other species like the Brünnich’s guillemot.

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These colonies can range in size from tens to tens of thousands of birds and are typically found in bird cliffs along the coast or even several kilometres inland. Black-legged kittiwakes are social birds and often feed in flocks, both on and under the surface of the sea.

They're skilled foragers, frequenting areas with up-welling waters and feeding on a variety of prey including small fish, invertebrates, and even offal or discarded fish behind fishing boats.

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Black-legged Kittiwakes are surface feeders, dropping from flight to take items off the surface of the water, or plunging into the water for prey just below the surface, but not diving deeply.

They forage while swimming, showing their adaptability in different aquatic environments.

Black-legged Kittiwakes are generally silent when seen in Washington, but on their breeding grounds, they are very vocal, repeating a call that sounds like their name.

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Black-legged kittiwakes breed in massive colonies, sometimes numbering in the tens of thousands, in bird cliffs along the coast.

These colonies can be found both along the coast and up to several kilometers inland, and they can be composed of just black-legged kittiwakes or mixed with other species like the Brünnich’s guillemot.

Black-legged kittiwakes often feed in large flocks, just above or below the surface of the sea, whether they're flying or swimming.

They also venture into icy waters and frequent areas where glaciers meet the sea to forage for food.

Outside of breeding season and as young birds, black-legged kittiwakes become pelagic, meaning they spend most of their time at sea.

Their diet consists mainly of invertebrates and small fish up to 15-20 cm long, but they also scavenge for food behind fishing boats or eat offal.

In Svalbard, common components of their diet include capelin, polar cod, amphipods, and euphausiids.

The arctic fox, arctic skua, great skua, and glaucous gull are all important predators and kleptoparasites of black-legged kittiwakes, targeting their eggs, chicks, and even adult birds.

The oldest recorded age for a black-legged kittiwake in Norway is 29 years.

The black-legged kittiwake is a fascinating bird species that thrives in coastal areas of the north Pacific and north Atlantic oceans. They can be found in large numbers on cliffs and ledges, particularly in North America and Europe.

One of the most interesting aspects of their behavior is their colonial nesting habits. They form monogamous pairs and take turns building their nests, incubating eggs, and rearing their young. This biparental care is a unique characteristic of the kittiwake species.

In fact, kittiwakes are known to nest in large colonies on cliffs, often in areas with sheer vertical faces. This is evident in their nesting sites on Staple Island in the outer Farne Islands. Their ability to utilize these extreme environments is a testament to their adaptability.

Historically, kittiwakes preferred nesting on natural cliffs and ledges, but in recent years, they have begun to adapt to nesting on man-made structures. For example, in the UK, they have been known to nest on buildings along the River Tyne, including the iconic Tyne Bridge in Newcastle.

Here are some key facts about kittiwake nesting:

The nest-building process is a complex and time-consuming task that requires both parents to work together. They start by forming a platform with mud and grass, followed by building a cup to keep the eggs safe. The nest is then lined with soft materials like moss, grass, or seaweed.

The Black-legged Kittiwake's conservation status is a complex issue.

Atlantic populations have experienced growth in recent years.

Their Pacific populations, however, fluctuate dramatically.

They are relatively insensitive to the direct effects of oil spills.

But they are indirectly affected by a reduction in prey species.

In years when food is scarce, their nesting success is significantly reduced.

The adults range farther from the nest and are away for longer periods of time, leaving the eggs and the young exposed.

This makes them more vulnerable to predators.

Years of near-total breeding failure for colonies have been observed in years when the diving birds in the same area do not experience a similar decline.

This suggests that surface feeders like the Black-legged Kittiwake may be responding to different environmental disturbances than diving birds.

For this reason, Black-legged Kittiwakes have been proposed as a good indicator species of marine health.

The black-legged kittiwake is a unique bird, but it's not the only one in its genus. The red-legged kittiwake is its closest relative, and it can be distinguished by its red legs.

One of the key differences between the two species is the color of their legs. The red-legged kittiwake, as its name suggests, has red legs, while the black-legged kittiwake has black legs.

In terms of size, the black-legged kittiwake is slightly smaller than a Ring-billed Gull, but larger than a Bonaparte's Gull.

If you're trying to identify a juvenile black-legged kittiwake, be aware that it can be confused with other species, such as the little gull and the Sabine's gull. However, the black-legged kittiwake's plumage has a distinctive black 'W' on the wing, which can help with identification.

Here are some key similarities and differences between the black-legged kittiwake and its similar species:

In flight, the black-legged kittiwake can be identified by its sleek appearance and long, narrow wings. It also has a distinctive way of foraging for food, dipping or plunging into the sea to seize small fish and other prey.

The black-legged kittiwake has a rich history in the world of taxonomy. Carl Linnaeus formally described the species in 1758.

The black-legged kittiwake was initially placed in the genus Larus, alongside other gulls. Linnaeus specifically mentioned the type location as northern Europe, but it's now restricted to Great Britain.

The genus name Rissa was introduced in 1826 by James Stephens. Stephens chose this name from the Icelandic word "rita", which means black-legged kittiwake.

The specific name tridactyla comes from the Ancient Greek word tridaktulos, meaning three-toed. This refers to the distinctive three-toed feature of the black-legged kittiwake's feet.

The English name "kittiwake" is derived from the bird's call, which sounds like "kittee-wa-aaake, kitte-wa-aaake".

The black-legged kittiwake population is in a precarious state, having declined by about 40% in just three generations. This decline is a major concern for the species' future.

The global population is estimated to be between 14.6 and 15.7 million individuals, with Europe accounting for more than 50% of the world's kittiwakes. This is a significant concentration of the species.

Commercial fisheries have a direct impact on the kittiwakes' food supply, particularly with the decline of sandeel populations in Europe. This has a ripple effect on the reproductive success of local kittiwake populations.

The global population of black-legged kittiwakes has declined by about 40% in just three generations, which is a staggering drop. The global population is estimated at 14,600,000-15,700,000 individuals and is in constant decline.

Europe represents more than 50% of the world's kittiwakes, while North America accounts for only 20% of the population. The individual distribution of kittiwakes varies quite a bit across the world.

The IUCN Red List has pointed out that all but one population of kittiwakes are in decline, with the exception of the small Canadian arctic population that's increasing at a rate of 1% per year. This is a significant exception to the overall trend of decline.

In 2017, the IUCN Red List moved the black-legged kittiwake from "least concern" to a "vulnerable" status on a global scale, highlighting the need for conservation efforts.

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Fisheries have a significant impact on the black-legged kittiwake's reproductive success due to the availability of their main food source, the sandeel.

Commercial fisheries in Europe have been known to deplete sandeel populations, affecting kittiwake reproduction.

The presence of fisheries also has indirect impacts on marine predators, including kittiwakes, through bycatch species.

Long-term research in the Gulf of Alaska has shown a direct correlation between food availability and reproductive success in kittiwakes.

Seabirds like kittiwakes can become entangled in fishing gear while trying to scavenge for food, often resulting in death by drowning.

The black-legged kittiwake is protected under the Migratory Bird Treaty Act of 1918, ratified by several countries including the US, Canada, Mexico, Russia, and Japan.

The black-legged kittiwake builds its nest on narrow ledges and rocky outcrops on cliffs, often on very small projections, and also uses artificial ledges like window sills on buildings.

The nest is a bowl-shaped structure made of earth and plant material held together with excrement, built by both parents.

In Svalbard, egg-laying typically occurs in the first half of June, with eggs having a light brownish background colour and darker speckles.

The normal clutch size is two eggs, but in more temperate areas, three-egg clutches are also common.

At fledging, juvenile kittiwakes can be identified by their distinctive black 'W' band across the length of their wings, which is a characteristic plumage they retain for their first year.

This black 'W' band is accompanied by whiter secondary and primary feathers behind it, a black hind-neck collar, and a black terminal band on the tail. Their solid black bill is also a giveaway.

A second-year juvenile will still have a black marking on their coverts and tail, but their bill will start to take on a greenish color. This is a transitional phase, and their plumage will continue to change until they reach maturity.

Here's a breakdown of the different plumage stages of juvenile kittiwakes:

The black-legged kittiwake builds its nests on narrow ledges and rocky outcrops on cliffs, often on vertical sea cliffs with very small projections.

These birds are quite adaptable and can even use artificial ledges, like window sills on buildings, to build their nests.

The nest itself is a bowl-shaped structure made of earth, plant material, and excrement, carefully crafted by both parents.

In Svalbard, egg-laying typically occurs in the first half of June, with eggs featuring a light brownish background color and darker speckles.

A normal clutch size is two eggs, but in more temperate areas, three-egg clutches are also common.

Both parents take turns incubating the eggs for about 27 days, with one egg sometimes hatching a day or two before the other.

The older nestling tends to grow faster and often outlives its younger sibling, with only the eldest surviving to fledging at five or six weeks of age.

Young kittiwakes are fed a varied diet of fish and crustaceans by both parents, which helps them grow strong and healthy.

Once they disperse, most immature birds don't return to their natal waters until their third summer.

The black-legged kittiwake reaches sexual maturity at an age of four to five years, after which they're ready to start their own breeding cycle.

Kittiwakes are known for their distinctive calls, which can be heard all day long. Their typical call sounds like a long "kit-ti-wake".

These birds have a wide range of calls, each serving a specific purpose. The female will often make a series of short high-pitched "squeak" calls before and during copulation, and also to beg for food from the male.

The kittiwake alarm call is a loud and urgent "oh oh oh oh" that can be heard across the colony when predators are present. This call is a crucial warning signal for the birds.

Kittiwakes have a distinctive call that sounds like a long "kit-ti-wake".

Their calls are incredibly varied, with different sounds for different situations. The female will often make a series of short high-pitched "squeaks" before and during copulation. This call is also used by the female to beg for food from the male.

The kittiwake alarm call is a loud and clear "oh oh oh oh" that can be heard all across the colony when predators are nearby. This call is a warning to other kittiwakes to be on the lookout for danger.

Kittiwakes will call all day, every day, for various reasons. They'll only stop calling when the sun goes down.

The Black-legged Kittiwake is a medium-sized gull, approximately 41 cm long. Adult birds weigh between 330–450 g.

Their distinctive black wing-tips make them easy to recognize from a distance. The sexes look very similar, which can make identification a bit tricky.

The back and upper sides of the wings are a slate-gray color, while the head, neck, and belly are white. The bill is a bright yellow, and the legs are black.

In winter plumage, the nape and sides of the neck turn grey, but the overall appearance remains the same. The juveniles have brown-black markings, including a band over the neck and a spot behind the eye.

Youngsters still retain dark markings on the wings and tail the following summer, but the colors grow fainter with increasing age.