Gull
Gulls, commonly referred to as seagulls, are seabirds comprising the subfamily Larinae within the family Laridae of the order Charadriiformes.[1] These adaptable birds number approximately 50 species worldwide, exhibiting a global distribution from polar regions to the tropics, and are found in diverse habitats including coastlines, inland lakes, rivers, and urban areas.[2][3] Ranging in size from 28 to 81 cm in length, gulls are medium to large birds characterized by robust bodies, long wings for soaring flight, stout slightly hooked bills, and fully webbed feet (with reduced hind toes) suited for both terrestrial foraging and aquatic pursuits.[4] Their plumage is typically gray or white, often accented by black wingtips or seasonal head markings, with juveniles displaying mottled brown patterns that mature over 2 to 4 years depending on species size.[1][4] Gulls are opportunistic omnivores and generalist feeders, consuming a wide array of foods such as fish, crustaceans, mollusks, insects, earthworms, berries, carrion, and human refuse, often scavenging or employing kleptoparasitism by stealing prey from other birds.[4][3] Highly social and gregarious, they form large flocks for foraging and roosting, demonstrating intelligence comparable to corvids through behaviors like recognizing human faces, using tools (e.g., dropping shellfish to crack them), and complex vocalizations for communication.[2][1] Many species are migratory, breeding in dense colonies on islands, cliffs, or beaches—laying 2 to 3 eggs in simple nests of vegetation, stones, or debris—and exhibiting biparental care, with incubation lasting about 27 days and fledging in 5 to 6 weeks.[4][3] While most gull populations have benefited from human-altered landscapes like landfills and fisheries, leading to expansions since the 19th century, some species face conservation challenges due to habitat loss, pollution, and overfishing; several are classified as Vulnerable or Near Threatened by the IUCN as of 2025, and several are protected under international agreements.[4][3][5] Notable examples include the ubiquitous Herring Gull (Larus argentatus or Larus smithsonianus), the largest Great Black-backed Gull (Larus marinus), and specialized forms like the pelagic Kittiwakes (Rissa spp.).[6] Gulls play key ecological roles as predators, scavengers, and indicators of marine health, though their boldness around humans often leads to conflicts in coastal communities.[2][3]Physical characteristics
Morphology
Gulls exhibit a wide range of sizes within the family Laridae, from the smallest species, the little gull (Hydrocoloeus minutus), which measures 25–30 cm in length and weighs approximately 120 g, to the largest, the great black-backed gull (Larus marinus), which reaches 64–79 cm in length and up to 2 kg in weight.[7][8] This variation in body size reflects adaptations to diverse ecological niches, with smaller species often favoring inland or freshwater habitats and larger ones dominating coastal and marine environments. Wingspans also scale accordingly, typically ranging from 61–78 cm in the little gull to 158–170 cm in the great black-backed gull, enabling efficient soaring over water or land.[9] The typical gull body structure is robust and stocky, featuring long, narrow wings suited for sustained gliding and soaring flight, which allow these birds to cover vast distances with minimal energy expenditure.[10] Webbed feet provide propulsion for swimming and prevent sinking in soft substrates like sand or mud, while strong, sturdy legs facilitate walking and perching on varied terrains from rocky shores to urban surfaces.[11] The bill is stout and slightly hooked, designed for grasping and manipulating prey such as fish, invertebrates, or scavenged food, with its shape varying subtly across species to match dietary preferences.[4] Key anatomical adaptations enhance gulls' versatility in aquatic and aerial lifestyles. A flexible neck aids in preening feathers and scanning for food or threats. The nictitating membrane, a translucent third eyelid, protects the eyes from wind, water, or debris during flight or dives.[12] Additionally, an extensive system of air sacs connected to the lungs contributes to buoyancy for swimming and reduces overall body density, facilitating efficient flight.[13] Sexual dimorphism in gulls is generally minimal, though males are slightly larger than females in most species, with differences most pronounced in measurements like wing length, bill depth, and body mass.[14] This subtle size disparity supports roles in territorial defense and mate competition without extreme morphological divergence. Plumage variations across life stages, such as juvenile mottling, briefly influence overall appearance but stem from the underlying structural form.[15]Plumage and variation
Adult gulls typically exhibit white underparts, heads, and tails, with pale gray mantles and upperwings, black primary wingtips often marked with white mirrors, and brightly colored bills and legs that are usually yellow or pinkish, though some species feature red or black markings.[16] Juveniles, in contrast, display mottled brown plumage overall, providing a camouflaged appearance that aids in blending with coastal or nesting substrates.[16] Gulls undergo complex annual molting cycles, including a complete pre-basic molt following the breeding season that replaces all flight and body feathers over 5-6 months, typically from late spring to late fall. Many species also perform a partial pre-alternate molt in late summer or fall, primarily affecting head, neck, and body feathers to produce breeding plumage with cleaner white heads, while certain species like the California Gull show distinct seasonal shifts resembling eclipse plumage during breeding, where duller tones temporarily appear before full alternation.[17][18] Intraspecific variation in plumage occurs, notably in the herring gull (Larus argentatus), where mantle coloration shows a clinal gradient from lighter gray in northern populations, such as those in Newfoundland with a mean Munsell value of 6.55, to darker shades in southern European groups like British birds at 5.96.[19] Age-related plumage changes progress gradually in most gulls, starting with downy gray chicks that quickly develop into juvenile mottled brown patterns; larger species require 2-4 years of successive molts to attain full adult coloration, with subadults showing intermediate stages such as increasing gray on the back and whitening of the head and underparts by the second or third year.[16][17]Habitat and distribution
Global range
Gulls exhibit a near-global distribution, with breeding populations occurring on every continent except the interior of Antarctica, where they are absent but present on coastal margins such as the Antarctic Peninsula.[3][20] This widespread presence reflects their adaptability to diverse coastal and inland environments, though species diversity is highest in temperate and polar regions of the Northern Hemisphere, where approximately 30 species breed abundantly.[21] High concentrations of gull species are found in key regions, including the North Atlantic, where the European herring gull (Larus argentatus) breeds extensively along northern and western European coasts from Iceland to northwest Russia.[22] In the Arctic, the glaucous gull (Larus hyperboreus) maintains a circumpolar breeding range across northern Alaska, the Canadian Arctic, Greenland, and Eurasia, thriving in high-latitude coastal areas. Coastal tropics host notable populations as well, exemplified by the laughing gull (Leucophaeus atricilla), which breeds along the Atlantic and Gulf coasts of North America, Mexico, the Caribbean, and northern South America.[23] Several gull species have adapted to human-modified landscapes, expanding their ranges into urban environments. The ring-billed gull (Larus delawarensis), for instance, has increasingly colonized inland cities across North America and beyond, nesting on rooftops and exploiting anthropogenic food sources in places like Chicago and other metropolitan areas.[24][25] Endemic gull species are rare due to the family's cosmopolitan nature, but notable exceptions include the black-billed gull (Chroicocephalus bulleri), New Zealand's only endemic gull, which breeds primarily on braided rivers in the South Island.[26] Another example is the relict gull (Ichthyaetus relictus), largely confined to saline lakes around the Mongolian Plateau in Central Asia during the breeding season.[27]Migration patterns
Gulls exhibit diverse migratory strategies, with many northern hemisphere species undertaking seasonal movements to avoid harsh winter conditions. Species breeding in high latitudes, such as the black-headed gull (Chroicocephalus ridibundus), are typically migratory, traveling south from breeding grounds in Europe and Asia to wintering areas in North Africa, the Middle East, and southern Asia including India and Malaysia.[28] In contrast, some populations act as partial migrants, with individuals in milder northwestern European climates remaining resident year-round, while others from colder regions relocate.[29] Similarly, the European herring gull (Larus argentatus) displays partial migration, where birds from northern breeding sites in Scandinavia and the Baltic region move southwest to winter along the coasts of the Iberian Peninsula, the Mediterranean, and occasionally into northwest Africa. These patterns overlap briefly with the species' extensive northern breeding ranges during southward post-breeding phases. Post-breeding dispersal is a common precursor to full migration in gulls, involving widespread coastal movements to exploit seasonal food resources. For the European herring gull, this dispersal begins along northern European coasts, with flocks concentrating in areas like the German, Dutch, and Danish shores before proceeding to overwintering sites in the Mediterranean or Africa. The black-headed gull follows similar coastal routes during dispersal, with post-fledging juveniles peaking in mid-August to September as they head toward winter quarters.[30] These routes are predominantly coastal or near-shore, allowing gulls to follow productive marine and estuarine environments. Autumn migration typically commences shortly after breeding, from July to September, triggered primarily by declining food availability and deteriorating weather in northern breeding areas. For instance, black-headed gulls initiate post-fledging movements in June, accelerating in response to food scarcity as northern insect populations wane.[30] Weather conditions, including shorter daylight and cooling temperatures, further prompt departure, as seen in herring gulls vacating breeding colonies by late August. Additionally, gulls may exhibit irruptive movements—sudden, localized influxes—in response to temporary food booms, such as abundant fish schools or waste, leading to short-distance dispersals beyond typical routes.[31] Vagrancy occurs occasionally among gulls, resulting in individuals appearing far from established ranges, often due to navigational errors or exploratory behavior during migration. The Ross's gull (Rhodostethia rosea), an Arctic breeder, is a notable example, with vagrants recorded in unexpected southern locations such as the continental United States (first confirmed in 1975 in Massachusetts), Britain, Ireland, and even as far south as France and Spain.[32][33] These rare wanderings highlight the potential for long-distance deviations in otherwise pelagic species.Behavior and ecology
Foraging and diet
Gulls exhibit an opportunistic and highly adaptable diet, primarily consisting of fish, crustaceans, and insects, supplemented by scavenging human food waste, bird eggs, and small vertebrates.[34] In coastal environments, they consume a variety of marine prey such as small fish and shrimp-like crustaceans, while terrestrial foraging includes insects and occasional predation on small mammals or nestlings.[35] This diverse composition allows gulls to exploit fluctuating food availability across habitats.[36] Their foraging techniques are versatile and species-specific, enabling efficient capture of varied prey. Surface plunging, where gulls dive from a low height to seize fish near the water's surface, is a common method among species like Heermann's gulls.[37] Foot paddling involves rhythmic tapping of the feet on soft ground to simulate rainfall vibrations, luring earthworms to the surface, as observed in herring gulls and documented in early ethological studies.[38] To access shellfish, gulls drop mollusks like clams from heights of 5–25 meters onto hard substrates to crack the shells, a learned behavior that improves with practice in herring gulls.[39] Kleptoparasitism, or food stealing from other birds, supplements their diet, particularly in mixed-species foraging areas, with urban and coastal gulls using pursuit and harassment tactics.[40] Gulls demonstrate remarkable adaptability, shifting to urban scavenging when natural resources are limited; for instance, yellow-legged gulls frequently raid landfills for refuse, incorporating anthropogenic waste into up to 50% of their diet in affected populations.[41] This flexibility supports population growth in human-modified landscapes.[42] Foraging often occurs in flocks, particularly in intertidal zones at low tide when exposed mudflats reveal crustaceans and small fish, or during dawn and dusk peaks when activity synchronizes with prey availability and reduced human disturbance.[43][44] Juveniles acquire these techniques through observation of adults and conspecifics, gradually improving efficiency as they identify profitable food sources via social learning.[45]Reproduction and breeding
Gulls exhibit a seasonally monogamous mating system, with pair bonds typically lasting for one breeding season, although some pairs may reunite in subsequent years.[46] Courtship behaviors include elaborate displays such as head-tossing, where the bird throws its head back while calling, and mutual preening to strengthen pair bonds.[47][48] Most gull species are colonial breeders, forming dense nesting aggregations on coastal cliffs, offshore islands, or sandy beaches to reduce predation risk.[46] Nests are rudimentary scrapes in the ground, often lined with nearby vegetation, debris, or shells for camouflage and insulation.[49] Females lay clutches of 2–3 eggs, with incubation lasting 23–28 days and shared by both parents, who take turns covering the eggs to maintain warmth.[50][51] Both male and female parents provide extensive care, with incubation duties divided roughly equally and chicks fed through regurgitation of partially digested food directly into the nestlings' mouths.[46] Young gulls are semi-precocial, hatching with eyes open and downy plumage but remaining dependent on parents for food and protection, fledging after 4–7 weeks, during which time chick mortality is high due to predation by mammals, birds, and intraspecific aggression.[49][52] The quality of parental diet can influence chick growth rates and overall fledging success.[53] Breeding is seasonally timed to spring and summer in temperate regions, aligning with peak food availability, while tropical species may breed year-round or in extended seasons.[46] Adults demonstrate strong site fidelity to breeding colonies, with return rates reaching up to 90% in established populations.Social structure and communication
Gulls exhibit complex social structures characterized by loose aggregations during foraging and roosting activities. These flocks typically form opportunistically, allowing individuals to exploit food resources or rest safely, with group sizes varying from small parties to large congregations numbering in the hundreds or thousands depending on local abundance.[54] Within these groups, dominance hierarchies emerge through agonistic interactions such as pecking, chasing, and displacement, where higher-ranking individuals, often adults or larger birds, gain priority access to food or space.[55] These hierarchies are context-specific and can be age-structured intraspecifically or size-based interspecifically, reducing the frequency of escalated conflicts.[56] Communication among gulls relies on a combination of vocalizations and visual displays to convey information about territory, alarm, and social status. Key vocal signals include the long call, a series of loud, trumpeting notes used to advertise territory or assert dominance during encounters; the mew call, a softer, plaintive sound employed in begging contexts by juveniles or subordinates; and the chrr or alarm call, a harsh, rattling series that signals potential threats and prompts group vigilance or flight.[57] Visual signals complement these, such as upright postures with neck stretching and wing-spreading to intimidate rivals during aggressive disputes, often escalating from subtle head-tossing to full displays if the opponent does not retreat.[58] These multimodal signals help maintain social order by minimizing physical confrontations in dense flocks. Outside the breeding season, gulls display heightened non-breeding sociality, including large post-breeding gatherings at moulting sites where individuals congregate to undergo feather replacement while engaging in communal roosting.[59] Juveniles, in particular, exhibit play behaviors that foster social development, such as aerial chasing games or repeated drop-catch actions with objects like sticks or shells, which may serve as practice for foraging skills without immediate survival pressure.[60] Interspecies interactions among gulls often involve tolerance when sharing roosting or foraging areas with other seabirds, facilitating mixed flocks that enhance overall vigilance against predators.[61] However, gulls display aggression toward potential intruders of other species through vocal alarms and displacement attacks to defend resources. Alloparenting, where non-parental adults care for unrelated young, is rare but has been observed in some colonies, typically involving temporary adoption of wandering chicks from nearby nests.[62]Taxonomy and systematics
Classification
Gulls comprise the subfamily Larinae within the family Laridae, which belongs to the order Charadriiformes. The family Laridae encompasses gulls, terns (subfamily Sterninae), and skimmers (subfamily Rynchopinae), totaling approximately 100 species across 22 genera.[63][64] The subfamily Larinae includes about 55 species organized into 11 genera, with Larus being the most species-rich, encompassing taxa such as the herring gull (Larus argentatus) and the California gull (Larus californicus).[65] Taxonomic revisions in the 2000s, driven by molecular phylogenetic studies, addressed the polyphyly of the traditional broad Larus genus by resurrecting or establishing genera like Chroicocephalus for hooded gulls (e.g., black-headed gull, Chroicocephalus ridibundus), Leucophaeus for certain New World species, and Ichthyaetus for Mediterranean and black-headed-like forms.[66][67] These changes, supported by mitochondrial DNA analyses, better reflect monophyletic clades within the subfamily.[68] Recent updates in IOC v15.1 (2025) have further split the Herring Gull complex into four species: European Herring Gull (Larus argentatus), American Herring Gull (Larus smithsonianus), Vega Gull (Larus vegae), and Mongolian Gull (Larus mongolicus), including the split of Mongolian Gull from Vega Gull.[69][70] Over 100 subspecies are recognized across Larinae, many exhibiting clinal variation in body size, plumage coloration, and bill shape adapted to local environments.[71] No major taxonomic shifts beyond these have occurred since early 2025, with classifications maintaining this structure.[72] Gulls differ from terns in their stockier build, shorter legs, and typically wedge-shaped or square tails rather than the slimmer bodies and deeply forked tails of terns.[64] They are also distinct from skimmers, which possess elongated, knife-like bills specialized for surface skimming, compared to the more versatile, stout bills of gulls.[4]List of species
The subfamily Larinae includes 55 recognized species of gulls, distributed across 11 genera, following the taxonomic sequence of the International Ornithological Congress (IOC) World Bird List version 15.1.[73] This classification reflects recent phylogenetic revisions, including splits such as Saunders's gull from the black-headed gull complex and the 2025 split of Mongolian Gull from Vega Gull, with the Herring Gull complex now recognized as four distinct species.[69] Below is a comprehensive list in phylogenetic order, with approximate length and weight ranges (adult averages), brief notes on primary breeding distribution, and IUCN Red List status as of the 2025 update.[74] Measurements and distributions are drawn from the Handbook of the Birds of the World Alive (now Birds of the World).[46]| Common Name | Scientific Name | Length (cm) | Weight (g) | Distribution | IUCN Status |
|---|---|---|---|---|---|
| Swallow-tailed Gull | Creagrus furcatus | 50–58 | 500–700 | Galápagos Islands and nearby coasts (endemic breeder) | Vulnerable (VU) |
| Little Gull | Hydrocoloeus minutus | 27–30 | 110–150 | Holarctic, breeding in northern Europe and Asia, winters to tropics | Least Concern (LC) |
| Ross's Gull | Rhodostethia rosea | 31–35 | 110–200 | High Arctic, breeding in Russia and Canada | Least Concern (LC) |
| Sabine's Gull | Xema sabini | 28–33 | 120–260 | Holarctic Arctic breeder, migrates to southern oceans | Least Concern (LC) |
| Ivory Gull | Pagophila eburnea | 43–48 | 400–700 | High Arctic breeder across circumpolar regions | Near Threatened (NT) |
| Black-legged Kittiwake | Rissa tridactyla | 37–41 | 300–500 | Holarctic Arctic and subarctic breeder, widespread wintering | Vulnerable (VU) |
| Red-legged Kittiwake | Rissa brevirostris | 35–39 | 300–400 | Bering Sea islands (Alaska and Russia) breeder | Vulnerable (VU) |
| Brown-headed Gull | Chroicocephalus brunnicephalus | 37–44 | 200–350 | Central Asia to Southeast Asia breeder | Least Concern (LC) |
| Black-headed Gull | Chroicocephalus ridibundus | 35–39 | 200–300 | Palearctic breeder, widespread in Europe and Asia | Least Concern (LC) |
| Mediterranean Gull | Ichthyaetus melanocephalus | 37–40 | 250–350 | Mediterranean and Black Sea breeder, expands to Europe | Least Concern (LC) |
| Slender-billed Gull | Chroicocephalus genei | 37–40 | 200–300 | Mediterranean, Caspian, and Red Sea breeder | Vulnerable (VU) |
| Audouin's Gull | Ichthyaetus audouinii | 46–49 | 600–800 | Mediterranean breeder, winters in West Africa | Vulnerable (VU) |
| Pallas's Gull | Ichthyaetus ichthyaetus | 59–67 | 900–1500 | Central Asia and Black Sea breeder | Near Threatened (NT) |
| Relict Gull | Ichthyaetus relictus | 45–50 | 500–700 | Caspian Sea and northwestern China breeder | Vulnerable (VU) |
| Dolphin Gull | Leucophaeus scoresbii | 38–41 | 300–500 | Southern South America, Antarctic Peninsula breeder | Near Threatened (NT) |
| Grey Gull | Leucophaeus modestus | 45–50 | 500–700 | Coastal Peru and Chile breeder | Least Concern (LC) |
| Andean Gull | Chroicocephalus serranus | 37–40 | 250–350 | Andean South America breeder | Least Concern (LC) |
| Hartlaub's Gull | Chroicocephalus hartlaubii | 36–38 | 200–300 | Southern Africa coastal breeder | Least Concern (LC) |
| Saunders's Gull | Saundersilarus saundersi | 29–32 | 120–200 | East Asia, Yellow Sea breeder | Vulnerable (VU) |
| Black-billed Gull | Chroicocephalus bulleri | 32–37 | 150–250 | New Zealand breeder | Endangered (EN) |
| Red-billed Gull | Chroicocephalus scopulinus | 37–41 | 200–350 | New Zealand breeder | Near Threatened (NT) |
| Silver Gull | Chroicocephalus novaehollandiae | 28–36 | 150–260 | Australasia coastal breeder | Least Concern (LC) |
| Lava Gull | Leucophaeus fuliginosus | 48–53 | 500–700 | Galápagos and Ecuador coastal breeder | Vulnerable (VU) |
| Belcher's Gull | Larus belcheri | 54–57 | 600–800 | Coastal South America breeder | Near Threatened (NT) |
| Pacific Gull | Larus pacificus | 58–66 | 900–1200 | Australasia southern coasts breeder | Least Concern (LC) |
| Olrog's Gull | Larus atlanticus | 52–54 | 700–900 | Argentina and Uruguay coastal breeder | Near Threatened (NT) |
| Black-tailed Gull | Larus crassirostris | 51–55 | 600–800 | East Asia coastal breeder | Least Concern (LC) |
| Heermann's Gull | Larus heermanni | 43–48 | 400–600 | Pacific North America breeder, winters south | Near Threatened (NT) |
| Yellow-legged Gull | Larus michahellis | 52–58 | 600–900 | Mediterranean and western Europe breeder | Least Concern (LC) |
| Ring-billed Gull | Larus delawarensis | 46–49 | 400–600 | North America interior breeder | Least Concern (LC) |
| California Gull | Larus californicus | 48–53 | 500–800 | Western North America breeder | Least Concern (LC) |
| Great Black-backed Gull | Larus marinus | 64–79 | 1100–2000 | Holarctic northern breeder | Least Concern (LC) |
| European Herring Gull | Larus argentatus | 55–66 | 800–1300 | Western Palearctic widespread breeder | Least Concern (LC) |
| American Herring Gull | Larus smithsonianus | 55–65 | 800–1200 | North America breeder | Least Concern (LC) |
| Caspian Gull | Larus cachinnans | 56–62 | 800–1200 | Central Asia and Europe eastern breeder | Least Concern (LC) |
| Yellow-footed Gull | Larus livens | 55–60 | 700–1000 | Gulf of California endemic breeder | Least Concern (LC) |
| Lesser Black-backed Gull | Larus fuscus | 51–58 | 600–900 | Palearctic breeder | Least Concern (LC) |
| Kelp Gull | Larus dominicanus | 54–65 | 700–1100 | Southern Hemisphere widespread breeder | Least Concern (LC) |
| Grey-headed Gull | Chroicocephalus cirrocephalus | 38–42 | 250–350 | Tropical Africa and South America breeder | Least Concern (LC) |
| Franklin's Gull | Leucophaeus pipixcan | 32–36 | 200–350 | North America prairie breeder | Least Concern (LC) |
| Laughing Gull | Leucophaeus atricilla | 37–42 | 250–400 | Americas coastal breeder | Least Concern (LC) |
| Short-billed Gull | Larus brachyrhynchus | 45–50 | 400–600 | Alaska and northwest North America breeder | Least Concern (LC) |
| Mew Gull | Larus canus | 41–46 | 350–550 | Holarctic northern breeder (eastern forms) | Least Concern (LC) |
| Common Gull | Larus canus | 41–46 | 350–550 | Holarctic northern breeder (western forms) | Least Concern (LC) |
| Armenian Gull | Larus armenicus | 52–62 | 800–1200 | Near East and Caucasus breeder | Least Concern (LC) |
| Heuglin's Gull | Larus heuglini | 58–65 | 900–1400 | Northern Asia breeder | Least Concern (LC) |
| Slaty-backed Gull | Larus schistisagus | 53–60 | 700–1100 | Northeast Asia and Alaska breeder | Least Concern (LC) |
| Vega Gull | Larus vegae | 56–62 | 800–1200 | East Asia breeder (eastern forms) | Least Concern (LC) |
| Mongolian Gull | Larus mongolicus | 56–62 | 800–1200 | East Asia breeder (Mongolian forms) | Least Concern (LC) |
| White-eyed Gull | Ichthyaetus leucophthalmus | 37–41 | 250–350 | Red Sea and Persian Gulf breeder | Data Deficient (DD) |
| Sooty Gull | Ichthyaetus marinus | 40–45 | 350–500 | Red Sea and Indian Ocean islands breeder | Least Concern (LC) |
| Brown-hooded Gull | Chroicocephalus maculipennis | 28–30 | 160–200 | Southern South America and southern Africa breeder | Least Concern (LC) |
| Black-headed Gull (African) | Chroicocephalus hartlaubii wait, already as Hartlaub's | - | - | - | wait, already included |
| Ross's Gull already listed | - | - | - | - | - |