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Unmasking the Fascinating World of Brown-Headed Gulls: Identification Behavior and Survival Strategies

The Brown-headed Gull, scientifically known as Chroicocephalus brunnicephalus, is a small gull species that is commonly found in coastal regions and wetlands in South and Southeast Asia. It is one of the most easily recognizable gulls with its brown head and bright red bill.

In this article, we will explore the identification of the Brown-headed Gull, including its field identification and similar species, as well as its plumages and molts.

Identification

Field Identification

The Brown-headed Gull is a small gull, measuring around 38 cm in length with a wingspan of approximately 84 cm. While the species is predominantly brown, it has a white underbelly and head with a distinct brown hood.

Juvenile birds have a darker brown plumage compared to adults. The bill of the Brown-headed Gull is strikingly red, while the legs and feet are a pale pink color.

Similar Species

The adult Brown-headed Gull can be easily distinguished from any other gull species due to the presence of its distinctive brown hood. However, juvenile birds may be confused with other similar gull species, including the Slender-billed Gull and the Black-headed Gull.

Slender-billed Gulls have a thin black bill and a darker brown plumage with a slight hunchback appearance. On the other hand, Black-headed Gulls have a black hood that extends down their back with a greyish-brown plumage.

They also have a smaller bill compared to the Brown-headed Gull.

Plumages

The Brown-headed Gull has a slight sexual dimorphism, with male birds having a slightly larger bill and being more robust in structure than females. However, the species does not have any distinct breeding or non-breeding plumages.

Molts

The Brown-headed Gull undergoes two molts in a year. The first molt occurs after the breeding season, where the gulls shed their breeding plumage and replace it with non-breeding plumage.

This molt usually occurs between June to September. The second molt takes place between January to March, where the species sheds its non-breeding plumage or winter coat and replaces it with breeding plumage for the breeding season.

In Conclusion,

The Brown-headed Gull is a small, easily recognized gull species found in coastal regions and wetlands in South and Southeast Asia. Despite being easily distinguished with its brown hood and red bill, the species can be confusable with similar species like the Slender-billed Gull and the Black-headed Gull.

The species does not have any distinct breeding or non-breeding plumages; however, it undergoes two molts a year, replacing its winter coat with breeding plumage during the breeding season. By understanding the identification, plumages, and molts of the Brown-headed Gull, one can appreciate the beauty and diversity of this gull species.

Systematics History

The Brown-headed Gull belongs to the family Laridae, which also includes other gull and tern species. The species was formerly classed with the genus Larus; however, recent genetic analyses have shown that the species belongs to the genus Chroicocephalus, which consists of small to medium-sized gulls.

Geographic Variation

The Brown-headed Gull is widely distributed across South and Southeast Asia, occurring from Pakistan to Thailand and extending eastward to the Philippines and Indonesia. The species is also a vagrant to other neighboring countries such as China, Korea, and Japan.

Subspecies

There are two recognized subspecies of the Brown-headed Gull:

1. Chroicocephalus brunnicephalus brunnicephalus: This subspecies breeds in the northern part of the species’ range, from Turkey and the Caspian region to India.

The subspecies typically has a paler back and wings compared to the southern subspecies. 2.

Chroicocephalus brunnicephalus edenpoli: This subspecies breeds in the southern part of the species’ range, from Pakistan to the Malay Peninsula. The subspecies typically has a darker back and wings compared to the northern subspecies.

Related Species

The Brown-headed Gulls are closely related to other small gull species that belong to the genus Chroicocephalus, including Black-billed Gulls (Chroicocephalus bulleri) of New Zealand and Red-billed Gulls (Chroicocephalus scopulinus) of Australia. These species are morphologically and genetically similar, indicating a close evolutionary relationship.

Historical Changes to Distribution

The Brown-headed Gull has a rich history of changing distributions, and the distributions have changed in response to various environmental factors such as climate change, water management practices, and human activities. In the 19th century, the Brown-headed Gull was widely distributed across the Indian subcontinent, extending up to Afghanistan and Kazakhstan.

However, in the early 20th century, the species began to decline in numbers in these regions due to the draining of wetlands for agriculture and increased industrialization. In contrast, the species’ range has expanded in some parts of its distribution in response to changing environmental conditions.

For instance, in the 1970s and 1980s, the species experienced a sudden increase in numbers in northern and western China due to large-scale irrigation projects that created new wetland habitats. The Brown-headed Gull’s range has also been influenced by natural events such as the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD).

In years when the IOD is positive, there is an increase in the intensity of the Indian monsoon, resulting in higher levels of precipitation across South Asia and Southeast Asia. These conditions are conducive to the growth and expansion of wetland habitats, providing suitable breeding and foraging grounds for the species.

Similarly, during years when there is an El Nino event, there is a decrease in precipitation across the Indian subcontinent, leading to drought and a decline in wetland habitats. This has resulted in a decline in the numbers of the species, as they depend heavily on wetland habitats for their survival.

In Conclusion,

The Brown-headed Gull is a widely distributed gull species that has undergone significant historical changes in its distribution range. The species is closely related to other small gull species within the genus Chroicocephalus and has two recognized subspecies with differing geographic distributions.

Human activities, climate change, and natural events such as ENSO and IOD have had a significant impact on the species’ distribution. Despite the challenges posed by changing environmental conditions, the Brown-headed Gull remains a resilient and adaptable species with a diverse distribution range.

Habitat

The Brown-headed Gull is a coastal gull species found in a variety of habitats, including mudflats, estuaries, lagoons, wetlands, and shallow freshwater bodies. The species is also known to inhabit rice paddies and irrigated agricultural fields during the non-breeding season.

The gull’s choice of habitat is dictated by the availability of food and breeding sites, with the species typically selecting habitats rich in aquatic invertebrates and small fish.

Movements and Migration

The Brown-headed Gull is a sedentary species in some parts of its distribution and migratory in others, with some individuals undertaking seasonal movements in response to changing environmental conditions. In southern parts of its distribution, the species is known to be a resident, with many individuals remaining in their breeding grounds year-round.

However, in northern parts of its distribution, such as the Caspian region and Kazakhstan, the species is known to undertake seasonal movements. During the non-breeding season, the gulls migrate southwards to the northern coast of the Arabian Sea, the Gulf of Oman, and the Indian subcontinent.

Juvenile birds are known to disperse widely from their natal grounds in search of suitable feeding and breeding sites. The gulls typically achieve breeding maturity at three years of age, after which they return to their natal grounds to breed.

The species is also known to undertake altitudinal movements in response to changing environmental conditions. For instance, during years of low precipitation, the gulls are known to migrate to higher altitudes, where there is greater availability of water bodies and food resources.

Similarly, during years of heavy precipitation, the gulls move to lower altitudes, where food and water resources become more abundant. The Brown-headed Gull has also been observed undertaking short-distance movements during the breeding season.

These movements are often associated with changes in water levels within the breeding habitat, with the gulls moving to new nesting sites in response to changing conditions. Migration routes and timing of the Brown-headed Gull’s movements are poorly understood, with limited data available on the specific routes and timing of the species’ annual movements.

However, recent studies have begun to shed light on the patterns and routes of the species’ movements. In South Asia, the Brown-headed Gull is known to undertake extensive movements between breeding and non-breeding habitats.

These movements are characterized by the establishment of distinct flyways, which link breeding grounds in Central Asia to non-breeding grounds in South Asia. The annual migration of the species to the southern parts of its range is thought to occur between August to November.

In Conclusion,

The Brown-headed Gull is a coastal species that is known to inhabit a variety of wetland and aquatic habitats across its distribution. The species’ movements are dictated by changing environmental conditions, with some individuals undertaking seasonal movements in response to changing food and water resources.

The species exhibits both resident and migratory behavior, with juveniles known to disperse widely in search of suitable habitats. Despite the limited data available on the species’ specific migration routes and timing, recent studies have begun to shed light on the patterns and routes of these movements.

Diet and Foraging

Feeding

The Brown-headed Gull is primarily a surface feeder, typically foraging in shallow water or on mudflats. The gulls forage singly or in small groups, using a variety of techniques to capture prey items.

The species is known to mimic the foraging behavior of other waterbirds, including terns and sandpipers, by hovering over the water’s surface and diving suddenly to capture prey. The gulls are opportunistic feeders, and their diet varies depending on the availability of food.

The species primarily feeds on aquatic invertebrates such as worms, mollusks, and crustaceans. The species is also known to feed on small fish, tadpoles, and amphibians.

Diet

During the breeding season, the Brown-headed Gull’s diet shifts to accommodate the needs of their young. The gulls feed their chicks with a higher proportion of small fish and other vertebrates to meet their nutritional requirements.

In addition to foraging in aquatic habitats, the species is also known to forage on land, feeding on insects, earthworms, and other invertebrates. The gulls have also been observed feeding on human refuse in urban areas, where they scavenge for food scraps and discarded waste.

Metabolism and Temperature Regulation

The Brown-headed Gull has a high metabolic rate to support its active foraging lifestyle. The gull has a high rate of oxygen consumption, which is necessary to fuel its high level of activity during foraging.

The species is also capable of regulating its body temperature in response to changing environmental conditions, allowing it to forage in a range of temperatures. The species’ response to changing temperatures is mediated by its ability to control blood flow to its feet and legs.

The gull can raise the temperature of its feet and legs above that of its core body temperature, allowing it to forage in low water temperatures without suffering thermal stress.

Sounds and Vocal Behavior

Vocalization

The Brown-headed Gull is a vocal species, with a variety of calls used to communicate with individuals within its group. The species’ calls are typically short and sharp, with a harsh quality that is characteristic of gull vocalizations.

The calls vary according to the context, with different calls being used during breeding, non-breeding, and foraging activities. In breeding colonies, the species’ calls are largely associated with aggressive and territorial behavior.

The gulls use loud vocalizations to assert their dominance over other individuals and to defend their territories from intruders. During the non-breeding season, the Brown-headed Gull’s calls become more subdued and varied, reflecting the species’ more placid behavior during this period.

In Conclusion,

The Brown-headed Gull is a highly adaptable species with an opportunistic feeding strategy that varies according to the availability of food. The species primarily feeds on aquatic invertebrates and small fish; however, it has also been observed feeding on small vertebrates and scavenging for food in urban areas.

The gull has a high metabolic rate and can regulate its body temperature in response to changing environmental conditions. The species is a vocal one, with a range of calls used to communicate with others in its group.

The gulls’ calls vary according to the context, with different calls used during breeding, non-breeding, and foraging activities.

Behavior

Locomotion

The Brown-headed Gull has a distinctive style of locomotion, with a low, heavy wingbeat and a characteristic glide. The species is a strong and agile flyer, capable of making abrupt changes in direction and speed.

The gull’s flight is accompanied by a buoyant and agile wingbeat, enabling it to maintain the high level of energy expenditure necessary for extended foraging and breeding.

Self Maintenance

The Brown-headed Gull has a highly efficient self-maintenance system, with a preening behavior that is essential for maintaining feathers’ condition. The gull’s preening behavior is used to align and clean its feathers, removing dirt and debris that can interfere with their aerodynamic function.

During preening, the gulls will also redistribute oil from the uropygial gland, which helps to waterproof the feathers and reduce heat loss.

Agonistic Behavior

The Brown-headed Gull exhibits a range of agonistic behaviors, which are centered around food and territoriality. During the breeding season, the gulls engage in a range of aggressive behaviors, including wing-flapping, bill-poking, and chasing, to assert their dominance over individuals and to defend their territories.

Sexual Behavior

Breeding

The Brown-headed Gull exhibits a monogamous breeding system, with pairs forming lasting bonds that endure beyond the breeding season. Breeding pairs typically engage in courtship behavior, involving a series of calls and displays that reinforce the bond between the pair.

The species’ breeding season typically lasts from March to August, depending on the local climate and environmental conditions. During the breeding season, the Brown-headed Gull selects a site for nesting that is close to a reliable source of food and water.

The gulls build their nests on the ground, typically in the vicinity of other gulls’ nests, forming dense breeding colonies that can contain thousands of pairs. The gull’s nest is typically a shallow scrape in the ground, lined with grass, feathers, and twigs.

The female lays one to three eggs, which are incubated by both parents for around 24-28 days. The eggs hatch sequentially, with the chicks hatching asynchronously over a period of several days.

During the breeding season, the Brown-headed Gull exhibits parental care behaviors, with both parents involved in brooding and feeding the chicks. The parents bring food to the nest, regurgitating small invertebrates and fish that are fed to the chicks.

The chicks fledge at around four weeks of age, after which they are capable of flying and foraging independently.

Demography and Populations

The Brown-headed Gull is a widespread and common species across its distribution, with a population estimated to be between 3.2 and 6.5 million individuals. The species has been classed as a species of ‘least concern’ by the International Union for Conservation of Nature (IUCN) due to its wide distribution and apparent stable population trend.

Despite the apparent stability of the species’ populations, the Brown-headed Gull is threatened by human activities and environmental factors such as climate change. Wetland destruction, hunting, and disturbance from human activities are among the most significant threats to the species’ survival, as are changes in climate and sea level that alter the availability of suitable breeding and foraging habitats.

In Conclusion,

The Brown-headed Gull exhibits a range of behaviors that are essential to its survival, including efficient self-maintenance, locomotion, agonistic, and sexual behaviors. The species is a monogamous breeder that forms lasting bonds between breeding pairs and exhibits parental care behaviors during the breeding season.

Despite being widespread and common, the species is threatened by human activities and environmental changes that alter the availability of suitable breeding and foraging habitats. The Brown-headed Gull is a highly adaptable and resilient species that has adapted to a range of environmental conditions, exhibiting a range of behaviors, including foraging, breeding, and self-maintenance behavior.

Its range has evolved over time as its habitat has changed and in response to human activity. Despite being threatened by human activities and environmental changes that alter their foraging habitats, the species remains relatively stable, with a wide distribution range across South and Southeast Asia.

The study of the Brown-headed Gull has shed light on the ways in which species cope with changing environmental conditions, illustrating the importance of conservation efforts in understanding the ecological significance of vulnerable and threatened species. The insights gained from research on the Brown-headed Gull will be invaluable for enhancing our understanding of

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