Great Black-backed Gull

Larus marinus

Great Black-backed Gull -- larger and darker than the Lesser Black-backed, with pink-grey legs

Kelp Gull/Southern Black-backed Gull Larus dominicanus
The Kelp Gull, also called the Southern Black-backed Gull (New Zealand), is the Southern Hemisphere version of the northern Great and Lesser Black-backed. It's dark colour back looks like the Great Black-backed, but in size it is between the Great and the Lesser Black-backed. Its common appearance around the coast and its habits are more akin to the Lesser Black-backed Gulls.
Southern Black-backed Gull with Blue Cod

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Lesser Black-backed Gull

Yellow-legged Gull

Herring Gull