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Unlocking the Hidden World of Black-Headed Gulls: Behaviors Migration and Diversity

Black-headed Gull, Chroicocephalus ridibundus, is a small gull that breeds in Europe and Asia but can be found in many parts of the world. In this article, we will explore the field identification, similar species, plumages, and molts of this bird species.

Identification

The black-headed gull can be easily identified by its black head and red bill. However, its plumage varies according to the season and age.

In breeding season, the adults have a dark brown mantle, black head, and bright red bill, which contrasts with the white body and wings. The legs and feet are also bright red.

In the non-breeding season, the hood is replaced by a white crescent behind the eye while the bill and legs are paler. Field

Identification

In flight, this gull species can be distinguished by its narrow-winged and buoyant flight, which is effortless and rapid.

The primary flight feathers are dark grey while the rest of the wing is light grey. The tail is white with a black band at its tip.

The body shape is similar to that of other gulls. While feeding on water, the gull’s slender bill is pointed downward, which allows it to catch small insects and plankton from the surface.

Similar Species

Black-headed gulls can be easily confused with other small gulls, especially due to their plumage variation. The common gull, which is a similar size, shape, and general appearance, has a green-yellow bill and doesn’t have the black hood of the black-headed gull.

The Mediterranean gull, which is slightly larger, has a black head like the black-headed gull, but also a black collar and wingtips. The little gull, which is smaller than the black-headed gull, has a dark ring around its eye, while the black-headed gull only has a dark ear spot.

Plumages

Black-headed gulls have four plumages: juvenile, first-year, second-year, and adult. Juvenile birds have a warm brown upperwing, head mottled brown, and yellow bill with a black tip.

In their first year, they begin to acquire their winter plumage, with white head feathers replacing the brown ones, but still retaining brown feathers on the upper wings. In their second year, the brown feathers are replaced with grey feathers.

The final adult plumage is acquired when the bird is two to three years of age.

Molts

Black-headed gulls go through a pre-basic and pre-alternate molt. The pre-basic molt, which happens in winter, changes the body feathers.

In contrast, the pre-alternate molt occurs in late winter and spring, and it changes the head and body feathers to the breeding plumage. After breeding, black-headed gulls undergo another molt, losing all the breeding feathers and returning to the non-breeding plumage.

In conclusion, the black-headed gull, Chroicocephalus ridibundus, is a fascinating bird species to observe. Its black head, red bill, and white body make it easy to identify.

This small gull is also easy to distinguish from other gulls by its narrow-winged and buoyant flight. By understanding the different plumages and molts, it is possible to appreciate the beauty of this gull throughout the year.

Systematics History

The family of gulls, Laridae, has long been a perplexing group for taxonomists, with varying opinions on the number of genera and species within the family. At different points in history, black-headed gulls have been classified within the genus Larus and the genus Chroicocephalus, with the latter being the current designation.

Geographic Variation

Black-headed gulls are widespread across Eurasia, and their range extends to some parts of Africa. Within their range, there is a considerable variation in plumage, size, and bill length.

This variation is partly influenced by geography, with birds in the north being larger than those in the south. The plumage is also influenced by the season, with breeding birds having a darker mantle, black head, and bright red bill compared to non-breeding birds.

Subspecies

There are currently eight recognized subspecies of the black-headed gull, each with varying characteristics. The subspecies are:

– Chroicocephalus ridibundus ridibundus: Found throughout Europe, Western Asia, and North Africa.

Breeds from Europe to western Asia and migrates south to North Africa in winter. Has a light grey mantle and a small size compared to other subspecies.

– Chroicocephalus ridibundus sibiricus: Found in eastern Siberia. Larger than the nominate subspecies, with a darker mantle and more extensive white in the tail.

– Chroicocephalus ridibundus kamtschatschensis: Found in eastern Russia and Kamchatka. Similar in appearance to the sibiricus subspecies.

– Chroicocephalus ridibundus delawarensis: Found in North America, breeds in northern Alaska, and winters in Mexico and California. Has a paler mantle and is smaller than the nominate subspecies.

– Chroicocephalus ridibundus bonapartei: Found in North America, breeds in the Great Lakes area, and winters in the Gulf of Mexico. Slightly larger than the nominate subspecies, with a darker mantle and a shorter bill.

– Chroicocephalus ridibundus occidentalis: Found in western North America, breeds in Alaska and winters in California and Mexico. Has a paler mantle and is smaller than the nominate subspecies.

– Chroicocephalus ridibundus gelastes: Found in West and Central Africa. Has a smaller bill and a darker mantle in breeding plumage compared to other subspecies.

– Chroicocephalus ridibundus cercinnus: Found in East and Southern Africa. Larger than the nominate subspecies, with a darker mantle in breeding plumage.

Related Species

The black-headed gull belongs to a group of small gulls known as “hooded gulls,” which are characterized by having a black hood in breeding plumage. The group includes related species such as the Mediterranean gull (Ichthyaetus melanocephalus), the laughing gull (Leucophaeus atricilla), and the Franklin’s gull (Leucophaeus pipixcan).

Historical Changes to Distribution

Black-headed gulls have been known to breed in Europe for thousands of years, with fossil records dating back to the Pleistocene epoch. However, human activity has deeply impacted their distribution over the centuries.

In the last few hundred years, black-headed gulls have expanded their range by taking advantage of newly created habitats, such as agricultural fields and urban environments. During the 19th century, black-headed gulls experienced a sharp decline in numbers due to hunting, egg collecting, and habitat loss.

This decline continued into the early 20th century, with the breeding range of the gulls retreating to the north.

However, in the mid-20th century, the establishment of nature reserves and measures to protect the birds led to a significant increase in their population.

This, in turn, allowed the breeding range of the black-headed gull to expand once again. In recent years, black-headed gulls have continued to adapt to human environments, which has led to the establishment of new breeding colonies in urban areas.

However, the dependence on human-created habitats has also led to a decline in gull populations in areas where traditional habitats such as wetlands have been lost. In conclusion, the black-headed gull is a complex species with a rich history of taxonomic changes and geographic variation.

The eight recognized subspecies showcase the enormous range of the bird, from North America to Africa and Asia. However, human activity continues to impact the distribution of the bird species, with changes in traditional habitats and the establishment of new environments.

As a result, the future of black-headed gulls remains uncertain, and ongoing conservation efforts are essential to ensure their survival.

Habitat

Black-headed gulls are adaptable birds that have been able to establish themselves in a range of habitats. They are primarily found near shallow wetlands, such as marshes, lakes, ponds, and rivers, where they can feed on fish, insects, and crustaceans.

In addition, the gulls have readily adapted to human environments, including landfills, agricultural fields, and urban areas, where they can scavenge for food.

Breeding colonies of black-headed gulls are typically found on islands or along the coast, with large colonies located on the shores of the Baltic and the Black Sea. The birds also breed on inland wetlands, such as those found in central Spain.

However, the breeding range of the species has expanded in recent years, with birds now breeding in urban environments across Europe, making use of buildings, rooftops, and bridges to nest.

Movements and Migration

Black-headed gulls are largely migratory birds, undertaking annual movements between their breeding and non-breeding grounds. Birds in Europe, for example, typically begin breeding in March and April, and birds in Central Asia begin breeding in May and June.

By August, gulls from northern breeding grounds begin migrating south, while those from southern breeding grounds begin migration in October. The migration patterns of black-headed gulls are complex and varied, with significant differences observed between populations.

Some birds migrate in a straightforward manner across the sea, while others fly overland. The gulls are also known to undertake a loop migration, flying north in the spring and south in the autumn over different routes, as seen in populations that breed in Central Asia.

Population sizes and migration patterns can vary due to environmental conditions, including climate and habitat changes. In recent years, there have been observations of black-headed gulls staying for longer periods in northern migratory areas during winter, made possible by improved food availability in landfill sites.

Such observations have resulted in the appearance of resident populations of the bird in certain areas. Local movements are also a regular part of the black-headed gull’s behavior.

Birds form groups outside the breeding season, often feeding in the same areas. These winter gull flocks may comprise of thousands of birds and may change in response to changing food availability.

In conclusion, black-headed gulls are adaptable birds that are capable of establishing themselves in a wide range of habitats. They are largely migratory birds, undertaking significant movements between their breeding and non-breeding grounds that can vary depending on environmental conditions.

While the general movements of the species are well documented, local movements and migration behavior of the species are still not fully understood and require further research to gain insights.

Diet and Foraging

Black-headed gulls are opportunistic feeders and have a diverse diet that varies depending on the season and location. They feed near water or on the flats, commonly feeding on fish, insects, and crustaceans.

The birds also feed on land in fields, meadows, and other areas, where they can find worms, insects, and other small animals.

Feeding

The feeding behavior of the black-headed gull is influenced by its environment and varies according to the time of day and tidal cycles. In aquatic environments, the gulls feed on floating insects and invertebrates on the surface of the water, where they can plunge down and catch prey.

When the tide goes out, gulls feed on exposed mudflats and feed on worms, clams, crustaceans, and other invertebrates. Black-headed gulls are also scavengers and feed on human-made environments.

They have been known to feed on food scraps and other organic materials found in landfills, garbage dumps, and other waste depots.

Diet

The diet of the black-headed gull is diverse and includes a range of aquatic and terrestrial prey. In aquatic environments, the gulls primarily feed on small fish species such as roach, rudd, and bream, and invertebrates such as shrimps, mollusks, and insects.

Terrestrial feeding often involves the consumption of earthworms and small insects, including ants, beetles, and caterpillars. The gulls also feed on seeds, berries, and other plant material in the warmer months when food availability is higher.

Metabolism and Temperature Regulation

Black-headed gulls have a unique metabolism that allows them to maintain a constant body temperature despite changes in the surrounding environment. This regulation is facilitated by the gull’s small size and extensive network of blood vessels and capillaries that allow for efficient heat transfer between the body’s internal organs and the environment.

To reduce heat loss, the gulls also fluff their feather for increased insulation.

Sounds and Vocal

Behavior

Vocalization

Black-headed gulls are highly vocal birds, with a diverse range of calls used for communication and social interaction. They use calls to establish territory, identify individuals, attract mates, and coordinate group movements.

The calls vary in tone and duration, with some more aggressive calls used when protecting food or chicks.

The communication among individual gulls includes a diverse range of calls.

The “chak” call is used to indicate aggression and territorial defense. The “kiaw” call is made in flight and can indicate distress or alarm.

The “kwee-yow” call is used during courtship and to attract a mate, while the “kee-yah” call is used to note competition among flock members.

Black-headed gulls also have a range of alarm calls which alert other birds in their flock.

The “pe-e-ip” alarm call is used when there is potential danger, and individuals may repeat it loudly to warn other birds. In conclusion, black-headed gulls possess diverse behaviors that permit their survival in different habitats across regions.

The birds’ metabolism and heat regulation are designed to complement their small sizes. The birds exhibit opportunistic feeding despite the season and thrive on several aquatic and terrestrial prey, along with scavenging.

The vocal communication of black-headed gulls is diverse and complex, contributing significantly to their social interactions and survival.

Behavior

Black-headed gulls exhibit a range of behaviors, including locomotion, self-maintenance, agonistic behavior, and sexual behavior. Understanding these behaviors is critical in deciphering the breeding and demography of the species.

Locomotion

Black-headed gulls are agile fliers, with their narrow wings and streamlined bodies allowing for effortless gliding across the skies and rapid changes in direction. When on land, they move around by walking or running and often take short, abrupt steps.

Self-Maintenance

Grooming is an essential part of the self-maintenance behavior of black-headed gulls. The birds perform regular preening and cleansing, which helps remove parasites and dirt from their feathers.

The birds use their beaks to remove dirt and dust from their feather and then groom each feather by drawing them through their bill and applying oil to maintain their waterproofing.

Agonistic

Behavior

Agonistic behavior in black-headed gulls involves physical aggression between individuals and can occur during feeding, territory defense, and mating.

The birds use their bills and feet to fight with other individuals, often in striking displays. The behavior is also used in social interactions, with individuals asserting dominance over other members of the group by displaying aggressive behaviors.

Sexual

Behavior

Black-headed gulls have a complex mating system that involves choosing a suitable mate and establishing a breeding territory. During courtship, males will perform aerial displays, fly low over the nest site, and offer nest material to the female.

The male will also perform an invitation display by walking around the female with his neck lowered and head bowed, sometimes holding a twig in his mouth. After mating, the female will lay up to four eggs and use nesting material brought by the male to construct the nest.

Breeding

Breeding of black-headed gulls is typically in the spring, with nesting occurring from late March to early April. The gulls form colonies, typically located on islands or on the shoreline, but in recent years have extended their breeding range to include urban environments.

Females will lay 3 to 4 eggs over several days, which are incubated for an average of 23 to 26 days before hatching. After hatching, chicks are fed by both parents, and their diet consists of insects and small fish that the parents bring them.

The chicks will fledge at around 35 to 40 days and will begin flying shortly after. However, the fledglings may remain with their parents for some time, learning how to fly and feed, before leaving to establish their territories.

Demography and Populations

Black-headed gull populations vary throughout their range, with some populations declining in the last few decades due to habitat loss and increased predation. However, some populations have increased or stabilized in recent years due to the establishment of protective measures and the creation of new habitats.

The global population of black-headed gulls is estimated to be around 5 million individuals. Population sizes vary between regions, with European populations estimated to be the largest.

The species is not considered to be globally threatened, and the IUCN lists it as “Least Concern.”

In conclusion, the behavior of black-headed gulls is diverse, with unique traits for self-maintenance, locomotion, agonistic behavior, and sexual behavior. By understanding these behaviors, it is possible to gain insight into the breeding and demography of the species.

The gulls are known to form colonies and breed in the spring, with chicks hatching after 23 to 26 days of incubation. An increased focus on habitat protection and sustainable development of different environments across regions is essential in ensuring that black-headed gulls continue to survive and thrive into the future.

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