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Discover the Fascinating World of Black-Legged Kittiwakes: Plumages Molts Diet and More!

The black-legged kittiwake is a seabird that belongs to the gull family. They are common in the Arctic and sub-Arctic regions, making their home on rocky shores and cliff faces.

In this article, we will explore the field identification, plumages, and molts of the black-legged kittiwake.

Field Identification

Black-legged kittiwakes are small to medium-sized gulls, measuring 15-18 inches in length and with a wingspan of 35-41 inches. The adult bird has a white head and underparts, a gray back, and black-tipped wings.

The bill is yellow and somewhat hooked at the end, while the legs are black. The juveniles are different from the adults, and their plumage may cause confusion with other gull species.

The head, back, and wings are brownish-gray, while the underparts are whitish. The bill is dark with a pale base, and the legs are black.

Similarly, breeders have some plumage differences. Black-legged kittiwakes have two types of breeding plumage: the non-breeding or winter plumage, and the breeding or summer plumage.

During the non-breeding season, the black marking on their heads fades, and their plumage becomes less colorful. In contrast, during the breeding season, the black tips on their wings get more substantial and a black band is present on their necks.

Similar Species

It is not uncommon to find other gull species that closely resemble the black-legged kittiwake. The Bonaparte’s gull, for example, has a similar size and shape, but their bill is smaller, and their legs are a dull pink.

The ivory gull has a white plumage similar to the adult black-legged kittiwake, but its bill is more substantial.

Plumages

The plumage of the black-legged kittiwake is a crucial characteristic that helps with its identification. They have three types of plumages: juvenile, winter, and breeding plumage.

Juvenile Plumage

From the moment that black-legged kittiwakes hatch, they have a downy feather covering instead of feathers. For almost three years, their plumage goes through several changes until they reach breeding age.

In their first year, juvenile black-legged kittiwakes have dark bills, dark eyes, and dark feather tips. Their bill gradually turns from dark to pale during their first winter, and their eyes lighten.

Winter Plumage

In the non-breeding season, black-legged kittiwakes have pale gray tips to the feathers on their backs and wings, making them appear more faded. The dark feathers on their heads and napes transform to a pale gray, and their black leg markings fade.

Breeding Plumage

When black-legged kittiwakes are ready to breed, their black leg markings become more intense. Their colored feathers, which were fading during winter, become more apparent, and the black tips on their wings become more extensive.

This breeding plumage helps to attract a mate.

Molts

The molting process is when birds replace their old feathers with new ones, allowing them to maintain healthy and functional flight capabilities. Black-legged Kittiwake has three molts throughout the year: pre-basic, pre-alternate, and definitive.

Pre-basic

Pre-basic molt happens during the late summer months, and during this time, the adult bird replaces its feathers on its wings, tail, and body.

Pre-alternate

This molt happens typically in early winter, and it is when black-legged kittiwakes shed their worn-out feathers to grow new ones that will aid them during the breeding season.

Definitive

Definitive molting is the last molting process of the year that takes place after the breeding season. During this process, birds shed their old feathers and replace them with new feathers to get them ready for the upcoming winter.

Conclusion

The black-legged kittiwake is a fascinating bird species that has unique features, such as its winter, breeding, and juvenile plumages, and the process of molting. By understanding these characteristics, bird enthusiasts can easily identify black-legged kittiwakes from other gull species and appreciate their contribution to the ecosystem as a whole.

Systematics History

The black-legged kittiwake is a seabird that belongs to the gull family, Laridae. The species was first described by Swedish naturalist, Carl Linnaeus, in his book Systema Naturae in the year 1758.

Since then, there has been much debate in the scientific community over how to classify the black-legged kittiwake.

Geographic Variation

Black-legged kittiwakes are found mainly in the Northern hemisphere, especially in the Arctic and sub-Arctic regions. They have a widespread distribution in the northern parts of the Atlantic and Pacific oceans.

While the species is generally non-migratory, some populations do move southward during harsh winters.

Subspecies

There are six recognized subspecies of the black-legged kittiwake. Each of these subspecies differs slightly in terms of their plumage, bill size, and geographic ranges.

1. Rissa tridactyla tridactyla – This is the nominate subspecies that breeds in the more northerly parts of the Atlantic, including Iceland and Greenland.

Their bills are relatively small compared to other subspecies. 2.

Rissa tridactyla pollicaris – This subspecies breeds in the north of Alaska and Canada. They have slightly larger bills than tridactyla subspecies.

3. Rissa tridactyla groenlandica – This subspecies is found in eastern Canada and Greenland.

They have larger bills than the other two subspecies. 4.

Rissa tridactyla krygiviksensis – This subspecies breeds on Wrangel Island in Russia. They have a distinct plumage, with darker underparts.

5. Rissa tridactyla alaskensis – This subspecies breeds in Alaska’s Aleutian Islands.

They have a robust build and larger bills than tridactyla subspecies. 6.

Rissa tridactyla pollicaris x groenlandica – This is the hybrid of pollicaris and groenlandica subspecies and is found in the High Arctic.

Related Species

Black-legged kittiwakes share many physical and behavioral characteristics with other gulls in the family Laridae. They belong to the gull subfamily, Larinae, which includes other gulls such as the herring gull, glaucous-winged gull, and laughing gull.

Historical Changes to Distribution

The distribution of the black-legged kittiwake has undergone significant changes in recent history. These changes can be attributed to various factors like climate changes, human disturbances, and fluctuations in food availability.

During the early part of the 20th century, black-legged kittiwake populations decreased in some locations due to exploitation for their eggs and feathers. However, with the adoption of protective regulations in many regions, populations began to recover.

Climate change has also played a significant role in changing the distribution of black-legged kittiwakes. The Arctic is one of the regions most affected by climate change, with temperatures rising at twice the global average.

This warming trend is causing changes in ice conditions, which further influences the distribution of the black-legged kittiwakes. Recent studies have shown that populations of black-legged kittiwakes in the eastern part of the Bering Sea have decreased by almost 66% since the 1980s.

This decline in population is linked to the declining abundance of small fish, such as capelin and sand lance, which is an essential component of their diet. Human activities have also contributed to changes in black-legged kittiwake distribution.

The species is prone to disturbances from human activities like oil exploration and shipping. The noise pollution caused by these activities can disrupt the communication and foraging behavior of the birds.

Some black-legged kittiwake populations have also been affected by invasive species like rats and introduced predators like foxes and mink. These non-native species can devastate bird colonies by eating eggs and chicks.

In conclusion, the black-legged kittiwake is a remarkable seabird with a broad distribution in the Northern hemisphere. The six subspecies of black-legged kittiwakes display slight variations in their physical characteristics and geographical range.

However, factors such as climate change, human activities, and invasive species continue to threaten the population stability and distribution of black-legged kittiwakes. It is essential that we take proactive measures to protect and conserve these fascinating birds.

Habitat

Black-legged kittiwakes are seabirds that live primarily in the Arctic and sub-Arctic regions.

Habitat selection for this species is associated with the presence of suitable nesting sites and food sources.

During the breeding season, black-legged kittiwakes prefer steep cliff ledges, rock formations, and corries that offer good visibility of their surroundings and protection from predators. The black-legged kittiwake’s nesting habitat is characterized by rocky ledges or cliffs, which provide a secure attachment point for their nests.

The nests are shallow depressions made of driftwood, seaweed, or grasses that the birds have collected from the surrounding area. The nesting sites frequently have other seabirds nesting nearby, creating a ‘seabird city.’

During non-breeding periods, black-legged kittiwakes may be observed offshore, congregated in large numbers feeding on schooling fish, krill, and small mollusks.

These coastal and offshore locations are essential to their survival.

Movements and Migration

The black-legged kittiwake species are considered mostly sedentary, with populations that exhibit a range of migratory behaviors. Some black-legged kittiwake populations undertake extensive migration, while others remain in their breeding locations year-round.

Black-legged kittiwakes that breed in the eastern Baltic, Scottish, and Norwegian populations are non-migratory, meaning they remain in their breeding locations throughout the year. The Eurasian population in the Kamchatka Peninsula is also largely sedentary, with some individuals undertaking short-distance movements.

On the other hand, black-legged kittiwakes that breed in Iceland, Greenland, Alaska, and Canada are known to undertake extensive migrations. These populations move southward during harsh winters, in search of more food in regions with milder climates.

The most extensive non-breeding aggregations of the species occur in the Pacific waters, particularly in the Bering and Chukchi Seas. Black-legged kittiwakes are capable of flying long distances.

In 2003, a band-recovered black-legged kittiwake was recorded to have flown 10,830 km from the Aleutian Islands to Namibia in southwestern Africa, which is the farthest distance recorded for the species. Black-legged kittiwakes have a well-structured migration pattern.

The migration begins in the fall with populations from Alaska, Canada, and Greenland flying southwards to the Aleutian Islands of Alaska, where they remain until the onset of winter. They then travel offshore to the Gulf of Alaska and subsequently to the Pacific Northwest, where they spend much of their non-breeding season.

In contrast, populations from Iceland and the northeastern parts of Canada undertake a southerly movement to the northeastern United States coast and the Canadian Maritime provinces, where they feed in the shallow inshore waters. Recent research has shown that migration patterns of black-legged kittiwakes are shifting due to climate change.

Changes in sea temperature, food sources, and wind patterns are affecting the migratory routes and destination of the species. For example, a shift in food sources in the Bering Sea has led to a change in the wintering locations of some populations.

In conclusion, black-legged kittiwakes are remarkable seabirds that exhibit a range of migratory behaviors. Their breeding and non-breeding habitats are critical to their survival, and the destruction or alteration of these habitats can significantly impact their populations.

The migratory patterns of black-legged kittiwakes are influenced by a range of factors, including food sources, sea temperature, and wind patterns. The recent changes in these factors due to climate change are affecting their migratory routes, with the potential to impact the populations’ future survival.

Diet and Foraging

Black-legged kittiwakes are opportunistic feeders and consume a wide variety of prey. Their primary food sources include fish, marine invertebrates, and zooplankton.

They forage mainly by surface-diving, hover-diving, or foraging in shallow waters.

Feeding

Black-legged kittiwakes have a unique feeding strategy that involves cooperative foraging. They forage alone or form groups of up to 100 individuals, which forage together.

This feeding behavior helps them locate food more efficiently and reduce the risk of predation. Kittiwakes often associate with other seabirds during foraging, which enables them to learn about the feeding behavior of other species, such as gulls, shearwaters, and albatrosses.

This association often results in mixed-species feeding flocks.

Diet

The diet of black-legged kittiwakes varies depending on their location and availability of prey. Arctic krill is an essential component of the diet of kittiwakes that breed along the Norwegian coast, while the ones that breed in the Gulf of Alaska feed on fish such as capelin and sand lance.

The availability of food during different seasons also influences the bird’s diet. In winter, they mainly feed on small fish, squid, and zooplankton, whereas in the breeding season, birds mainly feed on fish.

Metabolism and Temperature Regulation

Black-legged kittiwakes have unique adaptations for metabolic rate and temperature regulation. They have a high metabolic rate that enables them to metabolize food rapidly and efficiently.

They have more hemoglobin in the blood to ensure maximum oxygen delivery to their muscles during flight. During the non-breeding season, the metabolic rate of black-legged kittiwakes decreases, and they conserve energy.

They also have a thick layer of blubber under their skin that provides insulation to keep them warm in cold environments.

Sounds and Vocal

Behavior

Vocal communication plays an essential role in social behavior, mate selection, and breeding in black-legged kittiwakes. They have a sharp and distinctive call, which serves as a characteristic sound of the Arctic and sub-Arctic regions.

Vocalization

Black-legged kittiwakes have a variety of vocalization, including screeches, cackles, and screams. The primary purpose of these vocalizations is to communicate with other birds in their social group and to defend their territories from other birds.

During the breeding season, vocalizations play a crucial role in mate selection and regulating social behavior. Males use vocalizations to communicate with females, establish and maintain their territories, and attract other females.

Vocal communication is also essential during the incubation period, as males vocalize while incubating the eggs to signal their readiness to take over incubation duties. Black-legged kittiwakes also use vocal communication to coordinate their cooperative foraging, staying in touch while at sea, and signaling danger.

In summary, vocal communication is integral to the social behavior and vital activities of black-legged kittiwakes.

Behavior

Black-legged kittiwakes exhibit a range of interesting behaviors that allow them to survive in their harsh environments. These behaviors include locomotion, self-maintenance, agonistic behavior, and sexual behavior.

Locomotion

Black-legged kittiwakes have a range of movements that enable them to forage, migrate, and defend their territories. They have powerful flight and are efficient flyers, using updrafts and air currents to navigate long distances.

They also have excellent diving capabilities. They dive from the surface into the water to catch prey using the thrust of their wings to propel themselves downward.

Their webbed feet act as rudders to help them steer underwater.

Self-Maintenance

Black-legged kittiwakes have a range of sophisticated self-maintenance behaviors. They preen their feathers using their bills and feet, keeping them clean and free of parasites.

They also regurgitate food pellets that contain indigestible materials like fish bones and squid hooks to maintain their digestive system. Agonistic

Behavior

Agonistic behavior is an essential activity in social structures of birds.

Black-legged kittiwakes display agonistic behavior during territorial disputes, dominance displays, and foraging competition. Agonistic displays include bill-snapping, bill-to-bill contact, and aerial displays.

These displays help to establish dominance hierarchies and maintain the social order. Sexual

Behavior

Black-legged kittiwakes engage in a range of sexual behaviors during the breeding season.

These include pre-mating displays, pair-bonding, nest-building, incubation, and chick-rearing. Males use vocalizations and visual displays to attract females for mating, while females are selective about their mates.

Once paired, the couple engages in courtship feeding and preening and building the nest together.

Breeding

Black-legged kittiwakes breed in large colonies, occupying steep cliffs and rocky ledges along the seaboard. The nesting process starts in late April to early May, and both males and females contribute to nest-building.

They construct the nests using a range of materials, including grass, mud, and feathers. Female kittiwakes typically lay two eggs, and both parents take turns incubating the eggs.

During this period, they may perform mutual preening behaviors and use their bills to gently stimulate the eggs to speed up the development process. Chicks hatch in approximately three weeks, and both parents care for them.

During the first few days, the chicks are covered in downy feathers and are entirely dependent on their parents for food. Eventually, the chicks grow feathers and are ready to fledge and leave the nest.

Demography

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