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Uncover the Secrets of the Caspian Gull: Identification Plumage and Behaviour

Birdwatching is a popular pastime that has fascinated people for centuries because of the sheer diversity of species that exist worldwide. One of the most captivating birds to observe is the Caspian Gull, scientifically known as Larus cachinnans.

This lovely bird is a large gull that is widely distributed across Europe, Western Asia, and Central Asia. In this article, we will learn how to identify the Caspian Gull, distinguish it from other similar species, and examine its plumages, including the transitional molting stages.

Identification

The Caspian Gull is a large, robust bird that measures approximately 55-65 cm in length, with a wingspan of between 130-150 cm. It has a distinctive heavy bill, which is yellow with a red spot on the lower mandible.

The eyes are pale yellow, and the head and neck are white with a faint blush of pink. The upperparts are pale grey, and the wings have black tips and white trailing edges, which are particularly visible during flight.

The tail is white with a black band at the end, and the legs and feet are pink. Field

Identification

To differentiate the Caspian Gull from other similar gull species, there are key field markings to look out for.

For example, it is possible to distinguish the Caspian Gull from the Herring Gull, its closest look-alike, by examining the bill shape and size. The Caspian Gull has a shorter and thicker bill, with a more convex profile than the Herring Gull, which has a longer, thinner, and straighter bill.

Moreover, the Caspian Gull has a rounder head shape, which appears more compact than that of the Herring Gull, whose head is broader, flatter, and wedge-shaped.

Similar Species

Another difficulty in identifying the Caspian gull is its resemblance to the Great Black-backed Gull. Again, the Caspian Gull can be easily distinguished by its smaller size and lighter grey mantle.

Additionally, the Caspian Gull has a slightly steeper forehead and rounder head shape than the Great Black-backed Gull.

Plumages

Like most gulls, the Caspian Gull undergoes molt at various stages of its life cycle. Molting is the process through which birds renew their feathers, and each molt typically yields a different plumage.

The plumages of the Caspian Gull are as follows:

– Juvenile: The juvenile Caspian Gull has brown feathers on its body, head, and upper wings, with dark streaks on its pale underparts. The bill is all black, and the legs and feet are grey.

– First-winter: During this molting stage, the Caspian Gull’s body feathers begin to show a paler grey tone, whereas the head and upper wings remain dark brown. The beak’s upper is progressively showing a variable brown hue against black.

– Second-winter: At this stage, the plumage of the Caspian Gull becomes predominantly grey, with its head still retaining some brown feathers but less apparent than in the previous molt. Its bill starts to show more yellow hue.

– Adult winter: The plumage of an adult Caspian Gull is nearly entirely grey. The head, underparts, and upper wings are grey, whereas the tail is white with a black band.

The bill’s lower mandible has a distinct red spot, and the legs and feet are pink.

Molts

It is essential to note that the transition between plumages is a gradual process, and some individuals may show intermediate features of different plumages simultaneously. Additionally, the plumage of Caspian Gulls is variable, and birds from different regions may show distinct plumage features, making the identification process more challenging.

Conclusion

The Caspian Gull is a fascinating species with unique field identification and plumage characteristics that make it a worthwhile bird to observe. By familiarizing yourself with its key distinguishing features, you can easily distinguish it from other similar gull species that exist worldwide.

Constant birding and the desire to learn the distinctions within their plumage stages are essential to the study of bird identification.

Systematics History

The Caspian Gull, Larus cachinnans, is a member of the family Laridae and the order Charadriiformes. This bird species has a long and intricate systematics history with many taxonomic revisions and debates regarding its geographic variation, subspecies, and related species.

Geographic Variation

The Caspian Gull has a vast breeding range that covers a broad area of Europe, Asia, and parts of North Africa. However, beyond its primary breeding grounds, it is known to occur as a vagrant as far as the eastern United States and Canada.

Given its widespread distribution, the Caspian Gull exhibits a remarkable variation in its subtle morphology and plumage characteristics across different regions.

Subspecies

The International Ornithological Congress recognizes four subspecies of the Caspian Gull, which differ in size, bill and leg colours, and degrees of grey feathering. These subspecies are:

– Larus cachinnans cachinnans: This subspecies, commonly known as the Caspian Gull or the European Caspian Gull, is the most widely distributed and common of all subspecies.

The breeding range includes Eastern Europe, Crimea, and Black Sea coast. Its general plumage is pale with dark streaking on the head, throat, and breast, whereas the upper-wings are nearly entirely mouse-grey.

– Larus cachinnans michahellis: This subspecies, known as the Yellow-legged Gull or Western Yellow-legged Gull, inhabits the western Mediterranean basin, including the Iberian Peninsula, France, Italy, and the Balearic Islands. They have a pale yellow bill with a red subterminal spot and yellow legs and feet.

The head and body feathers are slightly darker than the European subspecies, and their backs are a shade darker than the pale grey upper-parts. – Larus cachinnans barabensis: This subspecies is found in central and northern Asia, including the Kazakh steppes, Siberia, Mongolia, and Lake Baikal.

The Baraba Steppe Gull, as it is commonly known, is the largest of all subspecies, with a bulkier body, a thicker bill, and conspicuously darker grey feathers on their wings. They have greenish-yellow legs and feet.

– Larus cachinnans heuglini: The Heuglin’s Gull, or Siberian Gull, is the most northerly of all subspecies, found primarily in the Arctic regions of Siberia. They have a global grey plumage with subtle streaking on their crown and hindneck.

Their bill is thicker and longer than the typical Caspian Gull, with a broader base and pale pinkish legs and feet.

Related Species

The Caspian Gull is considered to be a part of the “herring” group of gulls and is closely related to other species such as the Yellow-legged Gull, Herring Gull, Lesser Black-backed Gull, and Great Black-backed Gull. Within this group, the Caspian Gull is thought to be more closely related to the Yellow-legged Gull, as both subspecies share a recent common ancestor.

Historical Changes to Distribution

The Caspian Gull’s range has undergone significant historical changes over the last two centuries due to habitat loss, climate change, and human activities. The species’ original breeding range consisted primarily of the Black Sea coast and the Caspian Sea regions, but now the range extends as far as the Baltic Sea region.

This range expansion may be due to the increase in garbage dumps and urbanization throughout Europe. Some range contraction and loss have occurred in the easternmost part of the species range due to habitat modification and hunting in Russia and Kazakhstan.

The Caspian Gull’s non-breeding range has also seen some significant changes. The species used to overwinter in areas of coastlines and shallow seas near their breeding grounds.

However, with the increase in urbanization and human activities such as damming rivers, the species has been forced to expand its range and is now commonly observed in urban areas throughout the year. The Caspian Gull has become a common sighting in Western European cities, particularly in rubbish dumps and landfill sites, where they have found an abundance of food.

In conclusion, the Caspian Gull’s systematics history and geographic variation provide fascinating insights into its evolution. Its susceptibility to changes in habitat, climate, and human activities highlight the need for strategic conservation efforts.

Future studies on the Caspian Gull’s range and subspecies could yield even more insights into the species and aid in its protection.

Habitat

The Caspian Gull is a bird of open water and coastal habitats, feeding primarily on fish, invertebrates, and carrion. It inhabits a vast range of environments across its breeding and non-breeding season, from freshwater lakes and rivers to bays, estuaries, harbours, and coastal beaches.

The species also has an affinity for urban landscapes during the non-breeding season and can often be found foraging on landfills and surrounding urban areas. In its breeding range, the Caspian Gull prefers to nest on secluded beaches and islands in shallow freshwater or brackish lakes, often surrounded by open rocky fields or forest edges.

The ideal nesting habitat is one with tall grass or scrub vegetation, which provides ample cover, shade and helps to protect the nests from predators. The Caspian Gull typically breeds in colonies, which can range in size from a few pairs to hundreds of pairs, depending on the availability and productivity of nesting sites.

Movements and Migration

The Caspian Gull is a partial migrant, which means that some populations partially migrate or move short distances from breeding grounds in response to changing weather and food availability, while others are non-migratory or resident. The migration timing and patterns vary among different populations and subspecies.

The European subspecies, Larus cachinnans cachinnans, is mostly resident or performs short-distance movements in response to food scarcity or weather conditions. The subspecies found in the Mediterranean basin, Larus cachinnans michahellis, is primarily resident, with some individuals moving short distances during the non-breeding season.

The central Asian subspecies, Larus cachinnans barabensis, is a partial migrant that performs altitudinal migration, relocating to lower elevations during winter, making use of favoured habitat such as rivers along the foothills of Central Asia, such as the Ili and Chu rivers. Long-distance movements are rare, with no evidence of migratory movements across the Himalayas or Taklamakan desert.

The northernmost subspecies, Larus cachinnans heuglini, is a true migrant, breeding in Arctic Russia and spending the non-breeding season along the Asian East Coast or the western Indian Ocean. This subspecies has been recorded traveling south along the eastern coast of Asia to Thailand and Malaysia during the non-breeding season.

In conclusion, the movements and migration patterns of the Caspian Gull are complex and vary among different subspecies and populations. Understanding these patterns is essential for the conservation of the species and identifying critical areas for protection.

The species’ adaptability to urban landscapes during non-breeding season suggests that conservation efforts should also focus on protecting and restoring habitats in urban areas, which may decrease the competition with other scavengers.

Diet and Foraging

The Caspian Gull is an opportunistic forager that feeds on a vast array of food items, depending on the availability and abundance of resources in its habitat. Their primary feeding strategy is scavenging for carrion, and they can often be found feeding on fish, small mammals, and other birds’ remains.

They are also known to be active predators, opportunistic feeders of sewage, and forage for invertebrates on beaches and in freshwater habitats.

Feeding

Carrion scavenging is a crucial aspect of the Caspian Gull’s feeding strategy, particularly during non-breeding seasons when food resources may be scarce. They closely follow marine traffic and fishing vessels, as well as forage on rubbish dumps and municipal landfills for food.

The species has adapted to urban landscapes and is commonly observed foraging on waste sites, fast-food restaurants, and near people feeding the ducks. Predation is another essential aspect of their feeding strategy, with the species targeting smaller birds, rodents, and other small mammals.

They can also be seen preying on young seabirds such as Atlantic Puffins and Razorbills. Foraging in freshwater habitats is possible through the consumption of invertebrates, which makes up a significant portion of the Caspian Gull’s diet.

During breeding season, the species frequents small to medium-sized freshwater lakes and rivers in semi-open landscapes for feeding on insects and larvae, as well as small fish species that inhabit these bodies of water.

Diet

The Caspian Gull’s diet varies with respect to the season and geographic location. Due to availability and abundance, their primary source of energy changes throughout the year.

During the breeding season, their diet consists mainly of insects, both aerial and aquatic, as well as small mammal species. However, outside the breeding season, marine invertebrates such as crabs, starfish, and clams, as well as fish, become more prevalent in their diet.

Metabolism and Temperature Regulation

Caspian Gulls have a high metabolic rate which is essential for the species to maintain an active lifestyle. The species has an uncoupled proton conductance pathway, which helps to regulate body temperature and maintain a constant body temperature in changing weather conditions.

The proton conductance pathway generates heat through the field of the mitochondrial membrane, which may aid their immense tolerance of inhospitable environments such as urban areas.

Sounds and Vocal

Behavior

The Caspian Gulls, like many bird species, use vocalizations to communicate with each other. Vocal signals help to recognize other individuals, defend territories, locate mates, and signal alarm during danger.

The species exhibits diverse vocalization characteristics, with many individuals producing distinct calls, both during the breeding and non-breeding seasons.

Vocalization

Caspian Gulls are known to produce several different vocalization calls, ranging from long-distance communication to short-range communication. The calls during the breeding season consist primarily of advertising calls, which are used for territorial defence and courtship.

These vocalizations are loud and consist of repetitive croaking sounds. During the non-breeding season, they use more soft, low-pitched notes while foraging and communicating with each other.

The species also uses alarm calls, primarily in response to danger or when threatened. These calls are used to warn other individuals of impending danger or predators detected nearby.

Alarm calls are loud and fast paced, which can reverberate across wide distances. In conclusion, the experts in the field of bird studies work on improving methods of identification, role in shaping ecosystems, and conservation of the species.

The feeding, metabolism, and temperature regulation of the Caspian Gull are essential to understanding its role in its respective habitats. Sound vocalization and behaviour help to identify distinct calls for territory or courtship, as well as detecting nearby danger.

Behavior

The Caspian Gull is a social and interactive bird that exhibits complex behavior patterns during different life stages. These include locomotion, self-maintenance, agonistic, and sexual behaviors.

Locomotion

The Caspian Gull is an agile bird that is well adapted for aquatic and aerial locomotion. When foraging for food on the ground, it moves using a slow walk with a forward stance.

In the water, it uses its legs and webbed feet to swim with ease, and during flight, it glides effortlessly with slow, shallow wingbeats.

Self Maintenance

Caspian Gulls spend considerable time on self-maintenance behaviours, including preening and cleaning their feathers. These behaviours are essential for maintaining the structural integrity of feathers, which can wear out over time.

Contour feathers are critical for regulating body temperature and providing waterproofing, making them necessary for the species’ survival. Preening involves the rubbing of bill and head on feathers to spread oil from the preen gland for feather waterproofing.

Agonistic

Behavior

The Caspian Gull displays a range of agonistic behaviors when faced with potential threats or rivals. These behaviours include vocalizing, chasing, and aggressive posturing.

During breeding season, intense competition for valuable nesting spots and territory can lead to confrontations between individuals. Sexual

Behavior

The Caspian Gull’s sexual behavior begins during the breeding season when courtship displays begin between pairs.

These displays include vocalizations, head bobbing, and wing flapping. Mating occurs after the courtship is complete, and the male presents food to the female as part of the courtship ritual.

Breeding

The Caspian Gull is a monogamous species that forms long-term pair bonds during the breeding season. The breeding season varies depending on the region and latitude and can last from late April to early August.

Nesting is conducted in colonies, with the chosen site often being in locations previously used, and are chosen for the presence of vegetation cover to minimize predation, and are situated near water sources to facilitate foraging opportunities. The nest is a relatively simple structure with an open cup shape, built from twigs, stems, and grasses and lined with softer materials such as feathers, grass

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