Nature Journal
with Photos

Great Black-backed Gull Identification Tips
(Credit: U. S. Geological Survey)
General Information
- 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

- 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

- 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

- 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.
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