How to identify the Lesser Black-backed Gull

To correctly identify the Lesser Black-backed Gull (Larus fuscus), check each of these features. Birds can be tricky: habit, habitat, and call often confirm a sighting that a single photo cannot.

Size at a glance

Length

50-64 cm (20-25 in)

Wingspan

125-150 cm (49-59 in)

Weight

690-1300 g (1.5-2.9 lbs)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Adults have a dark grey to black mantle and wings, contrasting with white underparts and tail. The wingtips are black with prominent white 'mirrors'. Head, neck, and underparts are pure white in breeding plumage, becoming streaked with grey-brown on the head and neck in non-breeding plumage.

2. 2

   Beak shape

   Shape and color of the bill: a key field mark.

   Strong, slightly hooked yellow bill with a prominent red spot on the lower mandible.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Yellow iris with a red orbital ring.

4. 4

   Leg color

   Leg and foot color.

   Bright yellow.

5. 5

   Distinguishing features

   Standout features that separate this species.

   Dark mantle (darker than Herring Gull, paler than Great Black-backed Gull), yellow legs, and a red spot on the bill. The extent of darkness on the mantle varies geographically among subspecies.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   First-winter birds are mottled brown with a dark bill and pinkish-grey legs. They gradually acquire adult plumage over 3-4 years, with the mantle darkening and legs turning yellow. Second-winter birds show a darker, more uniform brown mantle and often a paler bill base. Third-winter birds are largely adult-like but may retain some brown in the wings or tail.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   Breeding adults have a clean white head and neck. Non-breeding adults develop fine grey-brown streaking on the head and nape, particularly around the eye and hindneck.

8. 8

   Sexual dimorphism

   How males and females differ.

   Males are typically slightly larger than females, but plumage is identical.

Key field marks

• Mantle Color. Observe the color of the back and upperwings. It should be a distinct dark grey to black, darker than Herring Gull but not as deep black as Great Black-backed Gull. Note that subspecies vary in mantle shade.
• Leg Color. Look for bright yellow legs. This is a crucial field mark distinguishing it from pink-legged Herring and Great Black-backed Gulls.
• Bill Color and Markings. Note the yellow bill with a prominent red spot on the lower mandible near the tip. The bill is typically less massive than that of a Great Black-backed Gull.
• Size. Assess its size relative to other gulls. It's a medium-large gull, smaller than Great Black-backed Gull but larger than Common Gull.
• Primary Pattern. In flight, observe the black wingtips with distinct white 'mirrors' (spots) on the outer primaries. The extent and shape of these mirrors can be useful for subspecies identification.
• Juvenile Plumage. Young birds are mottled brown. Look for the gradual darkening of the mantle and the change from dark bill/pinkish legs to yellow bill/yellow legs over several years.

Explore the Lesser Black-backed Gull