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I was focusing in the flock when a strange bird passed by:
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A pic to show a typical primary pattern on YLG:
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Several YLGs:
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An immature Caspian with a very hooked bill:
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Same bird from the other side:
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And then the odd one appeared!
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I think is a partly leucistic Heuglin's Gull:
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Details shows a subadult:
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