Comparison shot of 3 first-calendar year gulls of different species: from top to bottom: European Herring Gull Larus argentatus argenteus, Yellow-legged Gull Larus michahellis and Lesser Black-backed Gull Larus fuscus graellsii.
Note the subtle differences in the pattern on the tail, outer greater coverts and the inner primaries.
The photo was taken on 21 September 2014 in the harbour of IJmuiden, the Netherlands.
Gulls to the Horizon 