Kelp Gull, Larusdominicanus
The Kelp Gull is not easily detected in a crowd of laughing gulls. It blends in perfectly. This gull is noticeably larger than the laughing gulls.
Obviously this is an immature gull. They are known to wander.
The Kelp Gull forages on land or in water, rarely in the air. It feeds mainly on fish and crustaceans, but will scavenge when an opportunity arises. Like the Pacific Gull, the Kelp Gull habitually drops molluscs from midair onto rocks to smash them. http://birdlife.org.au/bird-profile/kelp-gull