Editing Gull (section)

==Behaviour==
===Diet and feeding===
[[Charadriiform]] birds drink salt water, as well as fresh water, as they possess [[exocrine gland]]s located in supraorbital grooves of the skull by which salt can be excreted through the nostrils to assist the kidneys in maintaining electrolyte balance.<ref>{{cite web|title = How do seagulls drink saltwater?|url = http://blogs.howstuffworks.com/2009/07/09/how-do-seagulls-drink-saltwater/|date = 9 July 2009|website= [[HowStuffWorks]]|access-date = 20 March 2013|archive-url = https://web.archive.org/web/20130327102901/http://blogs.howstuffworks.com/2009/07/09/how-do-seagulls-drink-saltwater|archive-date=27 March 2013 |url-status = dead| author = Dowdey, Sarah }}</ref>
Gulls are highly adaptable feeders that take a wide range of prey opportunistically. The food taken by gulls includes fish, and marine and freshwater [[invertebrate]]s, both alive and already dead; terrestrial [[arthropod]]s and invertebrates such as insects and earthworms; rodents, eggs, carrion, [[offal]], reptiles, amphibians, seeds, fruit, human refuse, and even other birds. No gull species is a single-prey specialist, and no gull species forages using only a single method. The type of food depends on circumstances; terrestrial prey, e.g. seeds, fruit and earthworms, is more common during the breeding season, while marine prey is more common in the nonbreeding season when birds spend more time on large bodies of water.<ref name = "HBW"/>
[[File:Gulls_foot_paddling.webm|thumb|left|[[Hartlaub's gull]] foot paddling, Cape Town]]
[[File:Black-tailed Gulls, Matsushima, Japan 2008-8-8.webm|thumb|left|Black-tailed gulls following a ferry in [[Matsushima]], Japan]]
Gulls not only take a wide range of prey, they also display great versatility in how they obtain it; prey can be caught in the air, on water, or on land. A number of hooded species are able to [[Hawking (birds)|hawk]] insects on the wing, although the larger species perform this feat more rarely. Gulls on the wing snatch items both off the water and off the ground, and they are able to plunge-dive into water to catch prey. Smaller species are more manoeuvrable and better able to hover-dip fish from the air. Dipping is common when birds are sitting on the water, and gulls may swim in tight circles or foot paddle to bring marine invertebrates up to the surface. 

Food is also obtained by searching the ground, often on the shore among sand, mud or rocks. Larger gulls tend to do more feeding in this way. Gulls may also engage in foot paddling in shallow water for invertebrates<ref>{{cite journal | vauthors = Buckley PA | title = Foot-paddling in four American gulls, with comments on its possible function and stimulation | journal = Zeitschrift für Tierpsychologie | volume = 23 | issue = 4 | pages = 395–402 | date = September 1966 | pmid = 5992179 | doi = 10.1111/j.1439-0310.1966.tb01603.x | s2cid = 9504887 }}</ref> or on wet grass for earthworms.<ref>{{Cite web |title=Dancing for their dinner |url=https://www.cbc.ca/documentaries/the-nature-of-things/dancing-for-their-dinner-gulls-in-vancouver-tap-dance-to-trick-worms-into-thinking-it-s-raining-1.7114080 |url-status=live |access-date=28 January 2025 |website=CBC Docs}}</ref> One method of obtaining prey involves dropping heavy shells of clams and mussels onto hard surfaces.<ref name="HBW" /> Gulls may fly some distance to find a suitable surface on which to drop shells, and there is evidently a learned component to the task because older birds are more successful than younger birds.<ref>{{cite journal|vauthors=Ingolfsson A, Estrella BT|title=The development of shell-cracking behaviour in herring gulls|journal=The Auk|year=1978|volume=95|issue=3|pages=577–579|doi=10.1093/auk/95.3.577|url=http://sora.unm.edu/sites/default/files/journals/auk/v095n03/p0577-p0579.pdf|access-date=30 March 2013|archive-date=4 November 2014|archive-url=https://web.archive.org/web/20141104060559/http://sora.unm.edu/sites/default/files/journals/auk/v095n03/p0577-p0579.pdf|url-status=live}}</ref> While overall feeding success is a function of age, the diversity in both prey and feeding methods is not. The time taken to learn foraging skills may explain the delayed maturation in gulls.<ref name="HBW" />

Gulls have only a limited ability to dive below the water surface to feed on deeper prey. To obtain prey from a greater depth, many species of gulls feed in association with other animals, where marine hunters drive prey to the surface when hunting.<ref name = "HBW"/> Examples of such associations include four species of gulls that feed around plumes of mud brought to the surface by feeding [[grey whale]]s,<ref>{{cite journal|vauthors=Harrison C|title=The Association of Marine Birds and Feeding Gray Whales|journal=Condor|year=1979|volume=81|issue=1|pages=93–95|url=http://sora.unm.edu/sites/default/files/journals/condor/v081n01/p0093-p0095.pdf|doi=10.2307/1367866|jstor=1367866|access-date=30 March 2013|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304052608/http://sora.unm.edu/sites/default/files/journals/condor/v081n01/p0093-p0095.pdf|url-status=live}}</ref> and also between [[orca]]s (the largest dolphin species) and [[kelp gull]]s (among other seabirds).<ref>{{cite journal| vauthors = Ridoux V |title=Feeding association between seabirds and killer whales, ''Orcinus orca'', around subantarctic Crozet Islands|journal=Canadian Journal of Zoology|year=1987|volume=65|issue=8|pages=2113–2115|doi=10.1139/z87-324|bibcode=1987CaJZ...65.2113R }}</ref>

Looking at the effect of humans on gull diet, overfishing of target prey such as sardines have caused a shift in diet and behaviour. Analysis of the yellow-legged gull's (''[[Larus michahellis]])'' [[Pellet (ornithology)|pellets]] off the northwest coast of Spain has revealed a shift from a sardine to crustacean-based diet.<ref name="doi.org">{{Cite journal|last1=Calado|first1=Joana G.|last2=Paiva|first2=Vítor H.|last3=Ramos|first3=Jaime A.|last4=Velando|first4=Alberto|last5=Munilla|first5=Ignacio|date=2020-02-05|title=Anthropogenic food resources, sardine decline and environmental conditions have triggered a dietary shift of an opportunistic seabird over the last 30 years on the northwest coast of Spain|url=https://doi.org/10.1007/s10113-020-01609-6|journal=Regional Environmental Change|language=en|volume=20|issue=1|pages=10|doi=10.1007/s10113-020-01609-6|bibcode=2020REnvC..20...10C |s2cid=211028229|issn=1436-378X|access-date=1 March 2021|archive-date=20 November 2023|archive-url=https://web.archive.org/web/20231120065041/https://link.springer.com/article/10.1007/s10113-020-01609-6|url-status=live|url-access=subscription}}</ref> This shift was linked to higher fishing efficiency and thus overall fish stock depletion.<ref name="doi.org"/> Lastly, closure of nearby open-air landfills limited food availability for the gulls, further creating a stress on their shift in diet.<ref name="doi.org"/> From 1974 to 1994, yellow-legged gull populations on [[Berlenga Island]], Portugal, increased from 2600 to 44,698 individuals. Analyzing both adult and chick remains, researchers found a mixture of both natural&nbsp;prey and human refuse. The gulls relied substantially on the Henslow's swimming crab (''[[Polybius henslowii]]''). Yet, in times when local prey availability is low, the gulls shift to human-related food. These temporal shifts from marine to terrestrial prey highlight the resilience of adult gulls and their ability to keep chick condition consistent.<ref>{{Cite journal|last1=Alonso|first1=Hany|last2=Almeida|first2=Ana|last3=Granadeiro|first3=José Pedro|last4=Catry|first4=Paulo|date=December 2015|title=Temporal and age-related dietary variations in a large population of yellow-legged gulls Larus michahellis: implications for management and conservation|url=http://link.springer.com/10.1007/s10344-015-0958-9|journal=European Journal of Wildlife Research|language=en|volume=61|issue=6|pages=819–829|doi=10.1007/s10344-015-0958-9|bibcode=2015EJWR...61..819A |s2cid=15258313|issn=1612-4642|access-date=7 March 2021|archive-date=20 November 2023|archive-url=https://web.archive.org/web/20231120065041/https://link.springer.com/article/10.1007/s10344-015-0958-9|url-status=live|url-access=subscription}}</ref> Human disturbance has also been shown to have an effect on gull breeding, in which hatching failure is directly proportional to the amount of disturbance in a given plot.<ref>{{Cite journal|last1=Robert|first1=Henry C.|last2=Ralph|first2=C. John|date=1975|title=Effects of Human Disturbance on the Breeding Success of Gulls|url=http://dx.doi.org/10.2307/1366103|journal=The Condor|volume=77|issue=4|pages=495|doi=10.2307/1366103|issn=0010-5422|jstor=1366103|access-date=2 March 2021|archive-date=20 November 2023|archive-url=https://web.archive.org/web/20231120065041/https://academic.oup.com/condor/article-abstract/77/4/495/5205586?redirectedFrom=fulltext|url-status=live|url-access=subscription}}</ref> Certain gull breeds have been known to feast on the eyeballs of baby seals and directly pilfer milk from the [[elephant seal]]'s teat.<ref>{{cite journal |last1=Palermo |title=Gruesome Meal: Seagulls Snack on Baby Seals' Eyeballs |journal=Live Science |date=2015 |url=https://www.livescience.com/51944-seagulls-eats-seal-eyeballs.html |access-date=23 March 2022 |archive-date=12 February 2022 |archive-url=https://web.archive.org/web/20220212040648/https://www.livescience.com/51944-seagulls-eats-seal-eyeballs.html |url-status=live }}</ref><ref>{{cite journal |last1=Gallo-Reynoso |title=Feral cats steal milk from northern Elephant Seals |journal=Therya |year=2010 |volume=1 |issue=3 |pages=207–211 |doi=10.12933/therya-10-14 |doi-access=free }}</ref>
{{gallery
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| perrow = 
| File:Seagull eating starfish.jpg | [[American herring gull]] eating a [[starfish]] at [[Plum Island (Massachusetts)|Plum Island]] Nature Preserve, Massachusetts, US
| File:Gull attacking coot.jpg | [[Western gull]] attacking an [[American coot]]. The gull is probably trying to steal food from the coot's bill.
| File:Huntington beach pier seagull 2023.jpg | Juvenile gull waiting for discarded human food on [[Huntington Beach Pier]], California, US
| File:Flying ducks.jpg | [[Lesser black-backed gull]]s in a [[feeding frenzy]]
| File:Sea Gull at Point Lobos State Natural Reserve, CA.jpg| [[Western gull]] at [[Point Lobos State Natural Reserve]], California, US
| File:Seagull taking off the Sandy Hook shore.jpg | Juvenile [[ring-billed gull]], [[Sandy Hook]] shore, New Jersey, US
| File:Birdsniper.jpg | [[European herring gull]] stealing food from a man's hand, [[Ostend]], Belgium
}}

===Breeding===
[[File:Kittiwakes.jpg|thumb|[[Black-legged kittiwake]]s nest colonially, but have tiny, closely packed territories.]]
[[File:Larus marinus eggs.jpg|thumb|The nest of a [[great black-backed gull]], with three typical eggs]]
[[File:Newborn seagull 03.jpg|thumb|Newborn baby gulls with parent]]
[[File:Seagull chicks.jpg|thumb|Two ring-billed gull chicks sitting amongst rocks]]
Gulls are [[Monogamy in animals|monogamous]] and [[Seabird colony|colonial]] breeders that display mate fidelity which normally lasts for the life of the pair. Divorce of mated pairs does occur, but it apparently has a social cost that persists for a number of years after the break-up. Gulls also display high levels of [[Philopatry|site fidelity]], returning to the same colony after breeding there once and even usually breeding at the same location within that colony. Gull colonies can vary from just a few pairs to over a hundred thousand pairs, and may be exclusive to that gull species or shared with other seabird species. A few species nest singly, and single pairs of [[band-tailed gull]]s may breed in colonies of other bird species. Within colonies, gull pairs are [[Territory (animal)|territorial]], defending an area of varying size around the nesting site from others of their species. This area can be as large as a {{nowrap|5-metre}} radius around the nest in the [[European herring gull]] to just a tiny area of cliff ledge in the [[kittiwake]]s.<ref name = "HBW"/>

Most gulls breed once a year and have predictable breeding seasons lasting for three to five months. Gulls begin to assemble around the colony for a few weeks prior to occupying it. Existing pairs re-establish their [[pair-bond]]s, and unpaired birds begin courting. Pairs then move back into their territories, and new males establish new territories and attempt to court females. Gulls defend their territories from rivals of both sexes using calls and aerial attacks.<ref name = "HBW"/>

Nest building is an important part of the pair-bonding process. Most gull nests are mats of [[wikt:herbaceous|herbaceous]] matter with a central nest cup. Nests are usually built on the ground, but a few species establish their nests on cliffs (the usual preference for kittiwakes), and some choose to nest in trees and high places (e.g. [[Bonaparte's gull]]s). Species that nest in marshes need to construct a nesting platform to keep the nest dry, particularly species that nest in [[tidal marsh]]es. Both sexes gather nesting material and build the nest, but the division of labour is not always exactly equal.<ref name = "HBW"/> In coastal towns, many gulls nest on rooftops and can be observed by nearby human residents.

[[Clutch size]] is typically three eggs, although some of the smaller gulls only lay two, and the swallow-tailed gull produces a single egg. Birds synchronise their laying within colonies, with a higher level of synchronisation in larger colonies. The eggs of gulls are usually dark tan to brown or dark olive with dark splotches and scrawl markings, and they are well camouflaged. Both sexes [[Egg incubation|incubate]] the eggs; incubation bouts last between one and four hours during the day, and one parent incubates through the night.<ref name = "HBW"/> Research on various bird species, including gulls, suggests that females form pair bonds with other females to obtain [[alloparental care]] for their dependent offspring, a behaviour seen in other animal species, such as elephants, wolves, and the [[fathead minnow]].<ref>{{cite journal | vauthors = Riedman ML | year = 1982 | title = The Evolution of Alloparental Care in Mammals and Birds | journal = The Quarterly Review of Biology | volume = 57 | issue = 4| pages = 405–435 | doi=10.1086/412936| s2cid = 85378202 }}</ref>

Lasting between 22 and 26 days, incubation begins after the first egg is laid but is not continuous until after the second egg is laid, meaning that the first two chicks hatch at about the same time, and the third some time later. Young chicks are brooded by their parents for about one or two weeks, and often at least one parent stays behind to guard the chicks until they [[fledge]]. Although the chicks are fed by both parents, early on in the rearing period the male does most of the feeding and the female most of the brooding and guarding.<ref name = "HBW"/>