Gull

About

Gulls (genus Larus and related genera within the family Laridae) are a diverse group of seabirds found worldwide. They are typically medium to large birds, usually grey or white, often with black markings on the head or wings. They are opportunistic feeders, highly adaptable, and often found in coastal areas, inland waters, and increasingly in urban environments. Their taxonomy is complex and has undergone significant revision.

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, up to 49 years recorded for some large species)

Diet

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

Physical characteristics

Plumage

Adult plumage typically features a white head and underparts, grey mantle (back and upperwings), and black wingtips, often with white 'mirrors'. Some species have dark heads (e.g., Black-headed Gull, Laughing Gull) during breeding season. Juvenile plumage is highly variable, often mottled brown or grey, gradually acquiring adult plumage over 2-4 years depending on the species.

Beak shape

Strong, slightly hooked bill, typically yellow with a red spot on the lower mandible in many large species (e.g., Herring Gull), or dark red/black in others. Bill size and color are important identification features.

Eye color

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

Leg color

Varies by species: pink, yellow, greenish-yellow, or dark red/black.

Distinguishing features

Overall size, mantle color (shade of grey), wingtip pattern (extent of black and white mirrors), bill size and color, leg color, and head pattern (hooded vs. white-headed) are key. The primary projection beyond the tail at rest is also useful.

Juvenile appearance

Juveniles are typically mottled brown, grey, or dusky, often with dark bills and legs. They undergo several molts, gradually transitioning through various immature plumages (first-winter, second-winter, etc.) before reaching full adult plumage. The exact sequence and appearance vary significantly between species.

Seasonal changes

Many species exhibit seasonal changes, most notably 'hooded' gulls (e.g., Black-headed Gull, Laughing Gull) which develop a dark brown or black head during the breeding season and revert to a white head with a dark ear spot in non-breeding plumage. White-headed gulls generally show less dramatic seasonal changes, primarily involving head streaking in winter.

Sexual dimorphism

Generally minimal, with males often slightly larger than females, but plumage is usually identical. Voice can sometimes differ slightly.

How to identify

1. 1

   Size and Shape

   Note the overall size (small, medium, large) and body proportions. Is it slender or robust? Does it have a long neck or short legs?

2. 2

   Mantle Color

   Observe the color of the back and upperwings. Is it very pale grey, medium grey, or dark grey/black? This is a primary field mark for many species.

3. 3

   Wingtip Pattern

   Crucial for identification. Note the extent of black on the primary feathers, the presence and size of white 'mirrors' (spots) on the wingtips, and the pattern of white trailing edges.

4. 4

   Head Pattern

   Is the head entirely white, streaked with grey/brown (winter plumage), or entirely dark (hooded gulls in breeding plumage)? Note any distinct dark ear spots or eye-rings.

5. 5

   Bill Color and Shape

   Note the color (yellow, red, black, bicolored) and the presence of a red or black spot on the lower mandible. Is the bill slender or heavy? Long or short?

6. 6

   Leg Color

   Observe the color of the legs and feet (pink, yellow, greenish, black, red). This can be a definitive feature for some species.

7. 7

   Juvenile/Immature Plumage

   Be aware that gulls take several years to reach adult plumage. Learn the distinct juvenile and various immature plumages for common species in your area, as they often look very different from adults.

8. 8

   Vocalizations

   Learn the distinctive calls of different gull species. Their 'voices' can be very helpful, especially for species that are difficult to distinguish visually.

9. 9

   Behavior and Habitat

   Consider where you are seeing the gull (coastal, inland, urban) and what it is doing (foraging, resting, flying). This context can help narrow down possibilities.

Habitat & range

Biomes

Coastal marine, freshwater wetlands, estuaries, agricultural fields, urban and suburban areas, landfills, open ocean.

Geographic range

Cosmopolitan, found on all continents including Antarctica (e.g., Kelp Gull). Most species are found in temperate and subpolar regions of the Northern and Southern Hemispheres.

Elevation range

Sea level to several hundred meters inland, occasionally higher when foraging over mountains or inland lakes.

Preferred environments

Coastal beaches, rocky shores, harbors, estuaries, large lakes, rivers, reservoirs, agricultural land, landfills, urban parks, and rooftops for nesting.

Behavior

Activity time

Diurnal, though some species may forage at night, especially in urban areas or under moonlight.

Feeding habits

Highly opportunistic and omnivorous. They forage by scavenging, surface-feeding, plunge-diving (shallow), and pirating food from other birds. Diet includes fish, marine invertebrates, insects, eggs and chicks of other birds, carrion, refuse, small rodents, berries, and seeds. They often follow fishing boats or scavenge at landfills.

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 can be aggressive, especially when defending food or nesting territories.

Flight pattern

Strong, buoyant flight with steady wingbeats. They are adept at soaring and gliding, especially in coastal winds. Often seen hovering or performing agile maneuvers when foraging. Can be quite graceful in the air despite their size.

Migration pattern

Many species are migratory, moving from northern breeding grounds to more southerly wintering areas. Others are resident or partially migratory, with populations at the northern extent of their range migrating while southern populations remain year-round. Migration routes are often coastal or follow major river systems.

Territoriality

Highly territorial during the breeding season, defending nest sites and immediate surroundings from conspecifics and predators. Outside breeding, they are less territorial, often foraging in large, loose aggregations.

Breeding & reproduction

Breeding season

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

Nesting habits

Colonial breeders, often forming large, dense colonies on islands, cliffs, coastal dunes, salt marshes, or increasingly on urban rooftops. Nests are typically scrapes on the ground, lined with vegetation, feathers, and debris. Some species build more substantial nests in vegetation.

Clutch size

1-4 eggs, most commonly 2-3.

Egg description

Typically 2-4 eggs (most commonly 3), oval to pyriform, variable in color from pale olive to buff or bluish-green, heavily spotted and blotched with dark brown, black, or grey. Egg size varies greatly with species.

Incubation period

23-30 days, shared by both parents.

Fledging period

35-60 days, depending on 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 share incubation duties and care for the chicks, providing food and protection until they fledge and often for some time thereafter.

Where to find

Field tips

1. Study Local Species. Familiarize yourself with the common gull species in your specific region and their typical plumages (adult, juvenile, winter, breeding). This will help you quickly narrow down possibilities.
2. Observe in Good Light. Gull identification relies heavily on subtle plumage details. Observe birds in good, natural light to accurately assess mantle color, wingtip patterns, and leg/bill colors.
3. Use a Scope or Binoculars. High-quality optics are essential for resolving the fine details needed for accurate gull identification, especially for distant birds or subtle differences.
4. Look for Age Classes. Pay attention to whether the bird is an adult or an immature bird. Immature gulls can be particularly challenging, so understanding their age-specific plumages is key.
5. Compare Side-by-Side. If possible, compare an unknown gull with a known species nearby. This can highlight subtle differences in size, shape, and plumage.
6. Listen to Calls. Gull calls are distinctive. Learning them can help confirm identification, especially when visual cues are ambiguous.
7. Be Patient and Persistent. Gull identification can be challenging due to their variability. Spend time observing their behavior, flight, and various angles to gather all possible clues.

Similar species

Quick facts

Family:

Laridae

Diet:

Omnivorous scavengers

Habitat:

Coastal, inland waters, urban areas

Sociality:

Highly social, colonial breeders

Migration:

Many species migratory

Plumage:

Grey and white with black wingtips (adults), mottled brown (juveniles)

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.
• The taxonomy of gulls is notoriously complex, with many species having hybridized, leading to ongoing debates and revisions in their classification.
• Some gull species, like the Kelp Gull, have expanded their range significantly due to human activities, becoming common in areas where they were historically rare.
• 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 'red spot' on the bill of many large gulls (e.g., Herring Gull) acts as a target for chicks, stimulating them to peck at it to solicit regurgitated food from parents.

Scientific classification

Kingdom

Animalia

Phylum

Chordata

Class

Aves

Order

Charadriiformes

Family

Laridae

Genus

Larus (and other genera within Laridae)

Species

Numerous species (e.g., Larus argentatus, Larus marinus, Larus delawarensis)

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