Gull

About

Gulls (genus Larus) are a widespread and diverse group of seabirds belonging to the family Laridae. They are typically medium to large-sized birds, characterized by their robust bodies, long wings, webbed feet, and strong, slightly hooked bills. Gulls are highly adaptable and opportunistic, found in a variety of coastal and inland habitats across the globe. They are known for their distinctive calls, social behavior, and often scavenge for food.

Size & lifespan

Length

25-79 cm (10-31 in)

Wingspan

61-170 cm (24-67 in)

Weight

100-2000 g (3.5 oz - 4.4 lbs)

Lifespan

10-30 years (species dependent, e.g., Herring Gull up to 49 years)

Diet

Omnivore (fish, crustaceans, insects, eggs, carrion, refuse, small mammals, berries, seeds)

Physical characteristics

Plumage

Adult plumage typically features a white head and underparts, a grey or black mantle (back and upperwings), and black wingtips often with white 'mirrors'. Juvenile plumage is usually mottled brown or grey, transitioning through several immature stages over 2-4 years to reach adult coloration. Specific patterns vary significantly between species.

Beak shape

Strong, slightly hooked, and often brightly colored (yellow, orange, red) with a gonydeal angle (a prominent bulge on the lower mandible). Bill color can vary with age and season.

Eye color

Usually dark, but can be pale yellow or reddish in some species, often with a distinct orbital ring (red, yellow, or orange).

Leg color

Typically yellow, pink, or reddish, varying by species and age. Some species have dark legs.

Distinguishing features

General gull shape, long wings, webbed feet. Species-specific features include mantle color (light grey to black), head pattern (hooded, white, streaked), bill size and color, leg color, and wingtip patterns (extent of black, presence/absence of white mirrors).

Juvenile appearance

Highly variable and complex. Juveniles are typically mottled brown or grey, often with dark bills and legs. They undergo several molts, gradually acquiring adult-like plumage over 2-4 years, making age determination challenging and species identification difficult without experience.

Seasonal changes

Many species exhibit seasonal plumage changes. Breeding plumage often features a clean white head (e.g., Herring Gull) or a dark hood (e.g., Black-headed Gull). Non-breeding plumage typically involves streaking or smudging on the head and nape, and sometimes duller bill/leg coloration.

Sexual dimorphism

Generally minimal, with males often slightly larger than females, but plumage is typically identical. Size differences are usually subtle and not reliable for field identification.

How to identify

1. 1

   Size and Shape

   Observe overall size (small, medium, large) and body proportions (slender vs. robust). This helps narrow down possibilities significantly.

2. 2

   Mantle Color

   Note the color of the back and upperwings. This ranges from very pale grey (e.g., Glaucous Gull) to medium grey (e.g., Ring-billed Gull) to dark grey (e.g., Lesser Black-backed Gull) to black (e.g., Great Black-backed Gull).

3. 3

   Leg Color

   Check leg color: pink, yellow, greenish-yellow, or dark. This is a crucial field mark for many species, especially adults.

4. 4

   Bill Color and Markings

   Note the bill color (yellow, orange, red, dark) and any distinct markings, such as a black ring, a red spot (gonydeal spot), or a dark tip. Bill size and robustness are also important.

5. 5

   Head Pattern (Adults)

   Observe if the head is clean white, streaked with grey/brown (non-breeding), or has a full dark hood (breeding). The extent and color of streaking can be diagnostic.

6. 6

   Wingtip Pattern

   Examine the pattern of black and white on the primary wingtips. This is often highly species-specific, including the extent of black, the presence and size of white 'mirrors' (spots), and the pattern of white trailing edges.

7. 7

   Juvenile/Immature Plumage

   Be aware that gulls take 2-4 years to reach adult plumage. Immature birds are often mottled brown/grey and can be very challenging to identify. Look for overall tone, bill color, and any emerging adult-like features.

8. 8

   Vocalizations

   Learn the distinctive calls of common species in your area. The 'long call' is particularly useful for identification.

Habitat & range

Biomes

Coastal areas (beaches, cliffs, estuaries, harbors), inland lakes, rivers, agricultural fields, urban environments, landfills, open ocean.

Geographic range

Cosmopolitan, found on all continents, including Antarctica. Most species are found in temperate and polar regions of the Northern Hemisphere, but several species occur in the Southern Hemisphere.

Elevation range

Primarily sea level to low elevations, but some species can be found at higher altitudes near large inland water bodies.

Preferred environments

Coastal waters, large inland lakes and rivers, estuaries, harbors, fishing ports, agricultural land, urban centers, and landfills. They are highly adaptable to human-modified landscapes.

Behavior

Activity time

Diurnal, primarily active during daylight hours for foraging and social interactions. May forage at night under bright moonlight or artificial light sources, especially in urban areas.

Feeding habits

Highly opportunistic and omnivorous. They feed on fish, marine invertebrates (crabs, mussels), insects, eggs and chicks of other birds, carrion, refuse from human activities, small rodents, berries, and seeds. They forage by surface-seizing, dipping, shallow-plunging, and scavenging.

Social behavior

Highly social, especially outside the breeding season, forming large flocks for roosting and foraging. They are colonial breeders, nesting in dense aggregations. Some species exhibit kleptoparasitism, stealing food from other birds.

Flight pattern

Strong, buoyant flight with powerful wingbeats. They are adept at soaring and gliding, especially in coastal winds. Often seen hovering or performing agile maneuvers when foraging. Can fly long distances during migration.

Migration pattern

Varies by species and population. Many northern populations are migratory, moving south for the winter. Southern populations tend to be resident or undertake shorter, localized movements. Migration can be extensive, covering thousands of kilometers.

Territoriality

Highly territorial during the breeding season, defending nesting sites and immediate surroundings. Outside of breeding, they are generally gregarious and less territorial, though individual feeding territories may be defended temporarily.

Breeding & reproduction

Breeding season

Typically spring and early summer, varying geographically (e.g., April-July in Northern Hemisphere).

Nesting habits

Colonial breeders, often forming large, dense colonies on coastal cliffs, islands, dunes, or inland near water bodies. Nests are usually scrapes on the ground, lined with vegetation, feathers, and debris. Some species may nest on buildings or other structures.

Clutch size

2-4 eggs (most commonly 3)

Egg description

Typically 2-4 eggs (most commonly 3), oval to pyriform in shape. Coloration varies from pale olive to buff or brownish, heavily spotted, blotched, or streaked with dark brown, black, or purplish markings.

Incubation period

23-30 days, varying by species. Both parents share incubation duties.

Fledging period

35-60 days, depending on the species. Chicks are semi-precocial, able to leave the nest shortly after hatching but remain dependent on parents for food and protection.

Parental care

Both parents participate in incubation, brooding, and feeding the chicks. Parental care continues for several weeks after fledging until the young are independent.

Where to find

Field tips

1. Observe Age and Plumage. Gulls have complex plumages that change with age and season. Try to determine if the bird is an adult, first-winter, second-winter, etc., as this will guide your identification process.
2. Focus on Key Field Marks. Prioritize mantle color, leg color, bill color/markings, and wingtip patterns. These are often the most reliable features for distinguishing species.
3. Compare Size and Structure. If multiple gull species are present, compare their relative sizes and overall build. A 'small' gull next to a 'large' gull can be very informative.
4. Listen to Calls. Familiarize yourself with the calls of local gull species. Vocalizations can be a definitive identification tool, especially for species that look similar.
5. Use a Field Guide Specific to Your Region. Gull identification can be challenging due to regional variations and numerous species. A good field guide tailored to your geographic area is essential.
6. Be Patient and Persistent. Gull identification requires practice. Don't get discouraged if you can't identify every individual. Focus on learning the common species first.

Similar species

Quick facts

Diet:

Opportunistic Omnivore

Habitat:

Coastal, Inland Water, Urban

Sociality:

Highly Social, Colonial Breeder

Migration:

Varies by species, many migratory

Key ID Features:

Mantle color, leg color, bill markings, wingtip pattern

Fun facts

• Gulls are highly intelligent birds, capable of complex problem-solving, tool use (e.g., dropping shellfish to break them), and learning from observation.
• Some gull species have adapted remarkably well to urban environments, nesting on rooftops and scavenging human refuse, leading to them being called 'sky rats' by some.
• The 'long call' of gulls is a complex vocalization used for territorial defense, pair bonding, and maintaining contact within colonies.
• Gulls have specialized salt glands above their eyes that allow them to drink saltwater and excrete excess salt, enabling them to thrive in marine environments.
• The genus Larus is part of a larger family, Laridae, which also includes terns and skimmers, though gulls are generally more robust and have broader wings than terns.

Scientific classification

Kingdom

Animalia

Phylum

Chordata

Class

Aves

Order

Charadriiformes

Family

Laridae

Genus

Larus

Species

Multiple species within the genus Larus

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