Great black-backed gull Larus marinus

Identification Tips:

• Very large gull
• Very large bill with distinct gonydeal angle
• Flat forehead and large bill give "mean" appearance

Adult alternate:

• Bright yellow bill with red spot at gonys
• Pink legs
• Yellow iris
• White head, neck, breast and belly
• Black mantle
• White tertial and scapular crescent
• Black primaries (do not contrast with back) with white tips and two white mirrors on outer primaries
• White tail

Adult basic:

• Like adult alternate but faint brown streaking on head

Juvenile/First-year:

• Black bill
• White head, neck, breast, and belly with very fine dark streaks
• Back and upperwings strongly checkered with dark brown and white
• Dark primaries
• White tail with fine bars and black terminal band
• White rump contrasts with back

Second-year:

• Pinkish bill with black tip
• Pale head, neck, upper breast, and belly , streaked finely with brown
• Dull brown upperwing coverts
• Black back
• White tail with black terminal band

Third-year:

• Like adult basic, but often lacks adult bill pattern, wingtip pattern, and often retains brown upperwing coverts and a partial tail band

Similar species:

Adults and subadults older than one year are recognizable by their black mantle. All other gulls (including Lesser Black-backed Gulls) are paler backed. First-year birds are similar to other gulls in their first winter, but have very pale heads and breasts and strongly checkered upperparts, unlike any other species. First-year Lesser Black-backed Gulls are perhaps most similar in that they have white rumps and pale heads and breasts, but are very differently proportioned being smaller-billed and much longer-winged, and even smaller in size than a Herring Gull.