Black-headed gull

Appearance

This gull is 38–44 cm long with a 94–105 cm wingspan and weighs from 190-400 g.

In flight, the white leading edge to the wing is a good field mark. The summer adult has a chocolate-brown head, pale grey body, black tips to the primary wing feathers, and red bill and legs. The hood is lost in winter, leaving just two dark spots. Immature birds have a mottled pattern of brown spots over most of the body. It breeds in colonies in large reed beds or marshes, or on islands in lakes, nesting on the ground. Like most gulls, it is highly gregarious in winter, both when feeding or in evening roosts. It is not a pelagic species and is rarely seen at sea far from coasts.

The black-headed gull is a bold and opportunistic feeder. It eats insects, fish, seeds, worms, scraps, and carrion in towns, or invertebrates in ploughed fields with equal relish. It is a noisy species, especially in colonies, with a familiar "kree-ar" call. Its scientific name means "laughing gull".

This species takes two years to reach maturity. First-year birds have a black terminal tail band, more dark areas in the wings, and, in summer, a less fully developed dark hood. Like most gulls, black-headed gulls are long-lived birds, with a maximum age of at least 32.9 years recorded in the wild, in addition to an anecdote now believed of dubious authenticity regarding a 63-year-old bird.

Distribution

To be found over much of Europe, except Spain, Italy and Greece. It is also found in across the Palearctic to Japan and E China. It is an occasional visitor to the east coast of North America.

And also in some Caribbean islands.

Reproduction

Eggshell removal is a behaviour seen in birds once the chicks have hatched, observed mostly to reduce risk of predation. Removing the eggshell acts as a way of camouflage to avoid predators seeing the nest. The further away egg shells are from the nest, the lower the predation risk. Black-headed gull eggs experience predation from different species of birds, foxes, stoats, and even other black-headed gulls. Although mothers show some form of aggressiveness when a predator is near, in the first 30 minutes, wet chicks can be easily taken by other black-headed gulls after hatching when the parents of the wet chick are distracted.

Black headed gulls also carry away other objects that do not belong in the nest. The removal of eggshells and other objects is important not only in the incubation period but also during the first few days after the eggs hatch. However, the removal process seems to increase as time goes on. The removal is done by both the male and female parents, normally lasts a few seconds and is done three times a year.

A black-headed gull is able to differentiate an egg shell from an egg by acknowledging its thin, serrated, white, edge. Therefore, the weight of the egg or eggshell does not play a role when determining its value.Other hypotheses have attempted to explain the survival value of black-headed gulls removing their eggshells from the nest, including:

# The sharp edges of the shells after hatching could harm the chicks
# The eggshell could somehow intrude during the brooding
# The eggshell could slip over the unhatched egg, creating a double shell
# Some of the moist organic material left from the shell could lead to a production of bacteria and mould

Uses

The eggs of the black-headed gull are considered a delicacy by some in the UK and are eaten hard boiled.