European herring gull

European herring gull
Breeding-plumaged adult on Heligoland
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Laridae
Genus: Larus
Species: L. argentatus
Binomial name
Larus argentatus
Pontoppidan, 1763, Denmark
Range of L. argentatus      Breeding range     Year-round range     Wintering range

The European herring gull (Larus argentatus) is a large gull (up to 26 in (66 cm) long). One of the best known of all gulls along the shores of western Europe, it was once abundant.[2] It breeds across Northern Europe, Western Europe, Central Europe, Eastern Europe, Scandinavia and the Baltic states. Some European herring gulls, especially those resident in colder areas, migrate further south in winter, but many are permanent residents, e.g. in the British Isles, Iceland, or on the North Sea shores. European herring gulls have a varied diet, including fish, crustaceans and dead animals as well as some plants.

While herring gull numbers appear to have been harmed in recent years, possibly by fish population declines and competition, they have proved able to survive in human-adapted areas and can often be seen in towns acting as a scavenger.

Taxonomy

The taxonomy of the herring gull/lesser black-backed gull complex is very complicated, different authorities recognising between two and eight species.

This group has a ring distribution around the Northern Hemisphere. Differences between adjacent forms in this ring are fairly small, but by the time the circuit is completed, the end members, herring gull and lesser black-backed gull, are clearly different species. The terminal forms don't interbreed even though they coexist in the same localities.[3]

The Association of European Rarities Committees recognises six species:

Subspecies

Two L. a. argenteus individuals on the shore of Coumeenoole Bay, Ireland
Bird Sound

The two following 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. Others such as the Association of European Rarities Committees and British Ornithologists' Union now regard them as one or two separate species.[4][5]

Several other gulls have been included in this species in the past but are now normally considered separate, e.g. yellow-legged gull (L. michahellis), Caspian gull (L. cachinnans), Armenian gull (L. armenicus) and Heuglin's gull (L. heuglini).

Description

Bird Sound

The male European herring gull is 60–67 cm (24–26 in) long and weighs 1,050–1,525 g (2.315–3.362 lb) while the female is 55–62 cm (22–24 in) and weighs 710–1,100 g (1.57–2.43 lb). The wingspan can range from 125 to 155 cm (49 to 61 in).[6][7][8][9] Among standard measurements, the wing chord is 38.1 to 48 cm (15.0 to 18.9 in), the bill is 4.4 to 6.5 cm (1.7 to 2.6 in) and the tarsus is 5.3 to 7.5 cm (2.1 to 3.0 in).[7] Adults in breeding plumage have a grey back and upperwings and white head and underparts. The wingtips are black with white spots known as "mirrors". The bill is yellow with a red spot and there is a ring of bare yellow skin around the pale eye. The legs are normally pink at all ages but can be yellowish, particularly in the Baltic population which was formerly regarded as a separate subspecies "L. a. omissus". Non-breeding adults have brown streaks on the head and neck. Male and female plumage is identical at all stages of development, however adult males are often larger.[10]

Juvenile (2 winter

Juvenile and first-winter birds are mainly brown with darker streaks and have a dark bill and eyes. Second-winter birds have a whiter head and underparts with less streaking and the back is grey. 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.[11]

Juvenile herring gull in Helsinki

Yellow-legged variety

Adult Larus argentatus with yellow legs to the right, its offspring has the normal pink colour. This bird is not to be confused with the always yellow-legged Larus michahellis. Photo from Warnemünde (harbour of Rostock), Mecklenburg-Vorpommern, Northern Germany.

At least in the South-West part of the Baltic Sea and surrounding areas the European herring gull (Larus argentatus) actually can be seen with yellow legs. This is not considered as a subspecies, since they regularly breed with grey/flesh-coloured legged herring gulls. The offspring may get yellow or normal coloured legs. It must not be confused with the in general yellow-legged Larus michahellis, which are more common in the Mediterranean area but single birds may reach more northern seas.

Similar species

Adult European herring gulls are similar to ring-billed gulls but are much larger, have pinkish legs, and a much thicker yellow bill with more pronounced gonys. First-winter European herring gulls are much browner, but second and third-winter birds can be confusing since soft part colours are variable and third-year herring gull often show a ring around the bill. Such birds are most easily distinguished by the larger size and larger bill of European herring gull.

The European herring gull can be differentiated from the closely related, slightly smaller lesser black-backed gull by the latter's dark grey (not actually black) back and upperwing plumage and its yellow legs and feet.

The smaller silver gull is largely confined to Australia.

Voice

The loud laughing call is well known in the Northern Hemisphere, and is often seen as a symbol of the seaside in countries such as the United Kingdom. The European herring gull also has a yelping alarm call and a low barking anxiety call.

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. It should also be noted that adult gulls in urban areas will also exhibit this behaviour when fed by humans.

Behaviour

Herring gull producing waste near Île-de-Bréhat

European herring gull flocks have a loose pecking order, based on size, aggressiveness and physical strength. Adult males are usually dominant over females and juveniles in feeding and boundary disputes, whilst adult females are typically dominant when selecting nest sites.[11] Communication between these birds is complex and highly developed —employing both calls and body language. The warning sounds to chicks are the most obvious to interpret.

The warning to their chicks sounds almost like a small dog that barks. If the danger gets closer the adult birds repeat this sound, and if a danger is considered very dangerous the "bark/sound" comes in sequences of three quick such sounds. If a chick is "grounded" the adult bird lifts and attempts to annoy the threat. If other adult birds are present in such situations, they actually begins to help in the same way. For instance, a person with a dog (or who chases the chick) may be attacked by many adult birds, even if just one chick is in danger. The warning sound from a flying bird to a flock of fully fledged birds sounds very different. And it seems that all kinds of gulls understand the "general alert warning sound" of all other gulls. There's little doubt that the gull's screaming in fact is a kind of communication. Or in other words "a language", of course limited to the present tense, but it still obviously includes rather complex matters, like "follow me".

Two identical vocalizations can have very different (sometimes opposite) meanings, for example —depending on the positioning of the head, body, wings and tail relative to each other and the ground in the calling gull.

Unlike many flocking birds, European herring gulls do not engage in social grooming and keep physical contact between individuals to a minimum. Outside the male/female and parent/chick relationship, each gull attempts to maintain a respectful 'safe distance' from others of its kind.

However the bird must be considered as social bird that dislikes being alone, and fights mainly occur over food or in order to protect their eggs and chicks. If 3–4 birds discover a piece of food, the first one to land by the food piece often fold their wings out (together with a sound) in order to proclaim that this piece of food is mine. This is very often opposed by another gull, and during a short fight a third bird may very well grab the piece of food that the two other birds argue about! However, if much food is found especially at a "dangerous location" (like in a backyard of 4–5 floor buildings) the bird who discovered the food then shouts on close-by gulls – and the gulls (also of other species) gather, and when the first bird dares to land in the "difficult to escape location", soon all others feel safe to land, and eat. If a lot of food is located at a more safe location, the gull who first discovers it also shouts on other gulls, but starts to eat without waiting for the arrival of others. The conclusion is that if there is more food than one bird can manage to eat at one time, the birds are helping each other.

During the winter large flocks can be seen at (snow free) fields (agricultural or grass). Especially if the ground is has a high degree of moisture. At first sight it appears that the birds are just standing there, but in a pair of binoculars it becomes evident that only their body is not moving – while the birds actually are trampling the soil, most likely in order to trick worms to crawl closer to the surface of the soil. During early spring and late autumn many herring gulls feed heavily on earthworms, but it is a very opportunistic bird that seems to have many sources of food. For instance in southern Scandinavia and Northern Germany this species has during the 20th century become the most common of all gulls, and the increase has mostly occurred in urban or semi-urban environments. The greater black-backed gull (Larus marinus) was around 1900 as common as the herring gull in the mentioned parts, but has not increased at all so much (if at all). There are though some signs of that the bigger gull has learned (adopted) some of the herring gull's behaviour within urban environments. Where the herring gull is breeding in coastal urban environment, the greater black-backed gull seems to do the same, but in a far minor scale.

Herring gulls are good at producing all three eggs into flying birds. This means that at least one (often two) of the newly flying chicks loses both their parents within days after first flight. Some of these can later be seen in flocks of smaller gulls like the black-headed gull (Chroicocephalus ridibundus) or the common gull (Larus canus). They are probably not welcomed in such flocks, but follow them for some months anyway, and do thereby learn where to find food. Lonely juvenile herring gulls born in urban environment can also be seen staying for a some weeks close to outdoor restaurants and similar facilities. By November or December most juveniles have found other "mates", usually in water close areas.

The herring gull doesn't need swimming, but seems to enjoy all kind of waters, especially on hot summer days. The herring gull can only catch slow creatures, like small crabs, which they often drop from some altitude in order to get them opened. The birds haven't got any real power in its jaws while biting, but it may "pick" with better strength. Fish on land, eggs of other birds, and helpless chicks of smaller ducks (and similar birds where the female is the only caretaker of up to 9 eggs and chicks) are about as much predator the bird gets. It's then far more successful as a scavenger. Like vultures, adult birds can dig their whole head and neck in to for instance a dead rabbit. Although not always appreciated by mankind due to their dropping and screaming, the herring gull must be regarded as a "natural cleaner", and just as with crow-birds they help by keeping rats away from the surface in urban environment. Not by killing rats but by eating the potential rat food before the rats get the chance. Unlike real scavengers, herring gulls also eat most kind of other things than meat, like wasted food of all kind, from bread to human vomits. They seldom eat fresh fruit, but windfalls and rotten fruit seems more tasteful.

It has long been believed that the European herring gull has extremely keen vision in daylight and a night vision ability that is equal or superior to that of humans[12]—however it is now known that this species is also capable of seeing ultraviolet light.[13] The European herring gull also appears to have excellent hearing and a sense of taste that is particularly responsive to salt and acidity.[12]

Parasites of European herring gulls include the fluke Microphallus piriformes.

Distribution

Ireland: Copeland Bird Observatory, Co Down.[14]

Britain: Since 2009, herring gulls in the United Kingdom have been on the red list of birds of conservation concern,[15] including County Durham.[16]

Europe: Recorded from all the coasts of Europe including the Mediterranean and occasionally inland.[17]

Diet

Feeding behaviours of the European herring gull.
Stealing an egg from a common murre
Fighting for a fish.

These are omnivores and opportunists like most Larus gulls, and will 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. European herring gulls may also dive from the surface of the water or engage in plunge diving in the pursuit of aquatic prey, though they are typically unable to reach depths of greater than 1–2 m (3.3–6.6 ft) due to their natural buoyancy.[18] Despite their name, they have no special preference for herrings — in fact, examinations have shown that echinoderms and crustaceans comprised a greater portion of these gulls' stomach contents than fish, although fish is the principal element of regurgitations for nestlings.[19] European herring gulls can frequently be seen to drop shelled prey from a height in order to break the shell. In addition, the European herring gull has been observed using pieces of bread as bait with which to catch goldfish.[20] Vegetable matter such as roots, tubers, seeds, grains, nuts and fruit is also taken to an extent.[11] It has been observed that captive European herring gulls will typically show aversion to spoiled meat or heavily-salted food, unless they are very hungry. The gull may also rinse food items in water in an attempt to clean them or render them more palatable before swallowing.[12]

European herring gulls may be observed rhythmically drumming their feet upon the ground for prolonged periods of time in a behaviour that superficially resembles Irish stepdancing. This is for the purpose of creating vibrations in the soil, driving earthworms to the surface, which are then consumed by the gull.[21] It is believed that these vibrations 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.[22]

Whilst the European herring gull is fully capable (unlike humans) of consuming seawater, utilizing 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 will drink fresh water in preference, if available.[11][19]

Courtship and reproduction

Eggs, Collection Museum Wiesbaden, Germany

During courtship, the hen will approach the cock on his own territory with a hunched, submissive posture whilst making begging calls (similar to those emitted by young gulls). If the cock chooses not to attack her and drive her away, he will respond by assuming an upright posture and making a mewing call. This is followed by a period of synchronised head-tossing movements, after which the cock will then regurgitate some food for his prospective mate. If this is accepted, copulation will follow. A nesting site will then be chosen by both birds.[11] European herring gulls are almost exclusively sexually monogamous and may pair up for life, provided that the couple are successful in hatching their eggs.[18]

Two to four eggs, usually three, are laid on the ground or cliff ledges in colonies, and are defended vigorously by this large gull. The eggs are a dark blotched, olive colour. They are incubated for 28–30 days. Breeding colonies are predated by great black-backed gulls, harriers, corvids, herons and raccoons.

Juveniles use their beaks to "knock" on the red spot on the beaks of adults to indicate hunger. Parents typically disgorge food for their offspring when they are "knocked".[23] The young birds are able to fly 35–40 days after hatching and fledge at six weeks of age. Chicks are generally fed by their parents until they are 11–12 weeks old but the feeding may continue up to six months of age, if the young gulls continue to beg. The male feeds the chick more often than the female before fledging, the female more often post-fledging.[11]

Like most gulls, European herring gulls are long lived, with a maximum age of 49 years recorded.[24] Raptors (especially owls, peregrine falcons and gyrfalcons) and seals (especially grey seals) occasionally prey on the non-nesting adults.[18]

Interactions with humans

Tearing open a bin bag
Stealing food from a man's hand
Perching on spikes designed to discourage perching birds
Rubbish bag designed to resist scavenging behaviour

The European herring gull is an increasingly common roof-nesting bird in urban areas of the UK, and many individual birds show little fear of humans. The Clean Air Act 1956 forbade the burning of refuse at landfill sites, providing the European herring gull with a regular and plentiful source of food. As a direct result of this, European herring gull populations in Britain skyrocketed. Faced with a lack of space at their traditional colonies, the gulls ventured inland in search of new breeding grounds. Dwindling fish stocks in the seas around Britain may also have been a significant factor in the gulls' move inland.[25]

The gulls are found all year round in the streets and gardens of Britain, due to the presence of street lighting (which allows the gulls to forage at night), discarded food in streets, food waste contained in easy-to-tear plastic bin bags, food intentionally left out for other birds (or the gulls themselves), the relative lack of predators and readily available, convenient, warm and undisturbed rooftop nesting space in towns and cities. Particularly large urban gull colonies (composed primarily of European herring gulls and lesser black-backed gulls) are now present in Cardiff, Bristol, Gloucester, London and Aberdeen.[25][26] to name but a few.

The survival rate for urban gulls is much higher than their counterparts in coastal areas, with an annual adult mortality rate of less than 5%. It is also common for each European herring gull pair to successfully rear three chicks per year. This, when combined with the long-lived nature of European herring gulls, 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.[26]

Once familiar with humans, urban European herring gulls show little hesitation in swooping down to steal food from the hands of humans. During the breeding season, the gulls will 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. Large amounts of gull excrement deposited on property and the noise from courting pairs and begging chicks in the summer months is also considered to be a nuisance by humans living alongside the European herring gull.[26]

Non-lethal attempts to deter the gulls from nesting in urban areas have been largely unsuccessful. The European herring gull is intelligent and will completely ignore most 'bird scaring' technology after determining that it poses no threat. 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). If nests are removed and eggs are taken, broken, or oiled, the gulls will simply rebuild and/or re-lay, or choose another nest site in the same area and start again.[26]

Man made models of birds of prey placed on top of buildings are generally ignored by the gulls once they realise they are not real, and attempts to scare the gulls away using raptors are similarly ineffective. 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.[27] European herring gulls are also naturally accustomed to predators (such as skuas and great black-backed gulls) living in the vicinity of their nest sites in the 'wild' and are not particularly discouraged from breeding by their presence.[26]

Despite the increasing number of urban European herring gulls in the UK, the species, when taken as a whole is declining significantly across the country, its population having decreased by 50% in 25 years.[28] In 2009, the RSPB placed the European herring gull on its 'Red List' of threatened bird species, affording it the highest possible conservation status.[29] In response, Natural England in January 2010, following a public consultation, removed the European herring gull from the list of species covered by its general licenses, which had previously permitted authorized persons (e.g. landowners or occupiers) to kill the birds 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.[28]

Gallery

References

  1. ↑ Symes, A. (2015). "Larus argentatus". IUCN Red List of Threatened Species (IUCN) 2015: e.T62030608A83943414. Retrieved 6 May 2016.
  2. ↑ Gilliard, E. Thomas (1958). Living Birds of the World. New York: Doubleday & Company. p. 174.
  3. ↑ Mayr, Ernst (1964). Systematics and the Origin of Species. New York: Dover Publications, Inc. ISBN 0-486-21212-2.
  4. ↑ "AERC TAC's Taxonomic Recommendations" (PDF). www.aerc.be. AERC TAC. 1 December 2003. Retrieved 5 May 2008.
  5. ↑ Sangster, George J.; Collinson, Martin; Knox, Alan G.; Parkin, David T.; Svensson, Lars (2007). "Taxonomic recommendations for British birds: Fourth report". Ibis 149 (4): 863–857. doi:10.1111/j.1474-919X.2007.00758.x.
  6. ↑ Pierotti, R.J.; Good, T.P. Poole, A., ed. "Distinguishing Characteristics — Herring Gull — Birds of North America Online". The Birds of North America Online. Ithaca: Cornell Lab of Ornithology. doi:10.2173/bna.124. Retrieved 6 July 2013.
  7. 1 2 Olsen, Klaus Malling; Larsson, Hans (2004). Gulls: of North America, Europe, and Asia. Princeton University Press. ISBN 978-0691119977.
  8. ↑ Harrison, Peter (1991). Seabirds: An Identification Guide. Houghton Mifflin Harcourt. ISBN 978-0-395-60291-1.
  9. ↑ Dunning, John B., Jr., ed. (1992). CRC Handbook of Avian Body Masses. CRC Press. ISBN 978-0-8493-4258-5.
  10. ↑ "Herring gull". All About Birds. Cornell Lab of Ornithology. Retrieved 6 July 2013.
  11. 1 2 3 4 5 6 Spencer, S.; Omland, K. (2008). "Larus argentatus (On-line)". Animal Diversity Web. Retrieved 12 June 2009.
  12. 1 2 3 Strong, R. M. (April 1914). "On the Habits and Behavior of the Herring Gull, Larus Argentatus Pont (Concluded)". The Auk 31 (2): 178–199. doi:10.2307/4071717. Retrieved 5 September 2013.
  13. ↑ Marcus, Adam (2006). "Feather Colors: What Birds See". Birder's World. p. 52. Retrieved 18 July 2007.
  14. ↑ Copeland Bird Observatory. Annual Report for 2010
  15. ↑ "Birds of Conservation Concern" (PDF). British Trust for Ornithology. 2009.
  16. ↑ Bowey, K.; Newsome, M. (2012). The Birds of Durham. Durham Bird Club. ISBN 978-1-874701-03-3.
  17. ↑ Peterson, R.; Mountfort, G.; Hollom, P.A.D. (1967). A Field Guide to the Birds of Britain and Europe (11th impression ed.). London: Collins.
  18. 1 2 3 Pierotti, R.J.; Good, T.P. (1994). Poole, A., ed. "Behavior — Herring Gull — Birds of North America Online". The Birds of North America Online. Ithaca: Cornell Lab of Ornithology. doi:10.2173/bna.124. Retrieved 5 November 2009.
  19. 1 2 Pierotti, R.J.; Good, T.P. Poole, A., ed. "Food Habits — Herring Gull — Birds of North America Online". bna.birds.cornell.edu. Ithaca: Cornell Lab of Ornithology. doi:10.2173/bna.124. Retrieved 7 June 2013.
  20. ↑ Henry, Pierre-Yves; Aznar, Jean-Christophe (June 2006). "Tool-use in Charadrii: Active Bait-Fishing by a Herring Gull". Waterbirds (The Waterbird Society) 29 (2): 233–234. doi:10.1675/1524-4695(2006)29[233:TICABB]2.0.CO;2.
  21. ↑ Tinbergen, N. (1960). The Herring Gull's World. New York: Basic Books, Inc. p. 297.
  22. ↑ Catania, Kenneth C.; Brosnan, Sarah Frances (22 October 2008). "Worm Grunting, Fiddling, and Charming—Humans Unknowingly Mimic a Predator to Harvest Bait". PLoS ONE 3 (10): e3472. doi:10.1371/journal.pone.0003472. PMC 2566961. PMID 18852902. Retrieved 28 December 2009.
  23. ↑ "National Audubon Society - Waterbirds - Herring Gull". audubon.org. Retrieved 6 July 2013.
  24. ↑ "AnAge entry for Larus argentatus". The Animal Ageing and Longevity Database. Retrieved 23 November 2008.
  25. 1 2 Harris, Paul (1 July 2004). "Gulls bringing fear to inland towns". The Daily Mail. Retrieved 16 June 2009.
  26. 1 2 3 4 5 Rock, Peter (May 2003). "Birds of a feather flock together". Environmental Health Journal. Retrieved 15 June 2009.
  27. ↑ "Lethal Bird Control (Culling)". Pigeon Control Advisory Service. Retrieved 17 May 2011.
  28. 1 2 "Guidance Note on applications for a licence to control gulls" (PDF). Natural England - Wildlife Management & Licensing. Retrieved 18 June 2010.
  29. ↑ Fitch, Davey. "Red alert for one fifth of UK's bird species!". The Royal Society for the Protection of Birds. Retrieved 18 June 2010.
  • Harris, Alan; Tucker, Laurel; Vinicombe, Keith (1994). The Macmillan Field Guide to Bird Identification. London: Macmillan. 
  • Harrison, Peter (1983). Seabirds - an identification guide. ISBN 0-7470-1410-8. 
  • Snow, D.W.; Perrins, C.M. (1998). Birds of the Western Palearctic. Vol. 1 (Concise ed.). Oxford: Oxford University Press. 

Further reading

External links

Wikimedia Commons has media related to Larus argentatus.
Wikispecies has information related to: Larus argentatus
This article is issued from Wikipedia - version of the Saturday, May 07, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.