They have a varied diet, including fish, crustaceans, as well as some plants, and are also scavengers, consuming carrion and food left by or stolen from humans.

[4] The Association of European Rarities Committees recognises six species: These taxa are classified as subspecies of Larus argentatus by some authorities such as the American Ornithologists' Union and Handbook of the Birds of the World.

Third-winter individuals are similar to adults, but retain some of the features of immature birds such as brown feathers in the wings and dark markings on the bill.

The European herring gull attains adult plumage and reaches sexual maturity at an average age of four years.

[12] At least in the south-west part of the Baltic Sea and surrounding areas, the European herring gull (L. argentatus) actually can be seen with yellow legs.

They must not be confused with the in general yellow-legged gull (L. michahellis), which are more common in the Mediterranean area, but single birds may reach more northern seas.

[16] European herring gull chicks and fledglings emit a distinctive, repetitive, high-pitched 'peep', accompanied by a head-flicking gesture when begging for food from or calling to their parents.

[16] European herring gull flocks have a loose pecking order, based on size, aggressiveness, and physical strength.

[20] These are omnivores and opportunists like most Larus gulls, and scavenge from garbage dumps, landfill sites, and sewage outflows, with refuse comprising up to half of the bird's diet.

It also steals the eggs and young of other birds (including those of other gulls), as well as seeking suitable small prey in fields, on the coast or in urban areas, or robbing plovers or lapwings of their catches.

[12] Captive European herring gulls typically show aversion to spoiled meat or heavily salted food, unless they are very hungry.

[27] These vibrations are thought to mimic those of digging moles, eliciting a surface-escape behaviour from the earthworm, beneficial in encounters with this particular predator, which the European herring gull then exploits to its own benefit in a similar manner to human worm charmers.

[28] Whilst the European herring gull is fully capable (unlike humans) of consuming seawater without becoming ill, using specialized glands located above the eyes to remove excess salt from the body (which is then excreted in solution through the nostrils and drips from the end of the bill), it drinks fresh water in preference, if available.

[29] When forming a pair bond, the hen approaches the cock on his territory with a hunched, submissive posture, while making begging calls (similar to those emitted by young gulls).

[12] European herring gulls are almost exclusively sexually monogamous and may pair up for life, provided the couple is successful in hatching their eggs.

The UK European herring gull population has decreased by 50% in 25 years[32] and it is protected by law: since January 2010, Natural England has allowed lethal control only with a specific individual licence that is available only in limited circumstances.

[35] (Previously, killing the species was allowed under a general licence obtainable by authorised persons (e.g. landowners or occupiers) under certain circumstances (e.g. to prevent serious damage to crops or livestock, to prevent disease, or to preserve public health or safety) without requiring additional permission beyond the general licence.

This, when combined with their long-lived nature, has resulted in a massive increase in numbers over a relatively short period of time and has brought urban-dwelling members of the species into conflict with humans.

[40] During the breeding season, the gulls also aggressively 'dive bomb' and attempt to strike with claws and wings (sometimes spraying faeces or vomit at the same time) at humans that they perceive to be a threat to their eggs and chicks—often innocent passers-by or residents of the buildings on which they have constructed their nests.

Rooftop spikes, tensioned wires, netting, and similar are also generally ineffective against this species, as it has large, wide feet with thick, leathery skin, which affords the seagull excellent weight distribution and protection from sharp objects (the bird may simply balance itself on top of these obstacles with little apparent concern).

Although they are intimidated by birds of prey, European herring gulls, in addition to being social birds with strength in numbers, are large, powerful, and aggressive as individuals and are more than capable of fighting back against the potential predator, particularly if they consider their chicks to be at risk; in fact, the gulls may actually pose a greater threat to a raptor than vice versa.