The kelp gull superficially resembles two gulls from further north in the Atlantic Ocean, the lesser black-backed gull and the great black-backed gull and is intermediate in size between these two species. This species ranges from in total length, from in wingspan and from in weight. Adult males and females weigh on average and respectively. Among standard measurements, the wing chord is, the bill is and the tarsus is. The adult kelp gull has black upperparts and wings. The head, underparts, tail, and the small "mirrors" at the wing tips are white. The bill is yellow with a red spot, and the legs are greenish-yellow. The call is a strident ki-och. Juveniles have dull legs, a black bill, a dark band in the tail, and an overall grey-brown plumage densely edged whitish, but they rapidly get a pale base to the bill and largely white head and underparts. They take three or four years to reach maturity.
Subspecies
There are five subspecies of kelp gull. The African subspecies L. d. vetula is sometimes split as the Cape gull, L. vetula. It has a more angular head and a smaller shorter bill. The adult has a dark eye, whereas the nominate kelp gull usually has a pale eye. Young Cape gulls have almost identical plumage to similarly aged kelp gulls.
Kelp gulls are omnivores like most Larus gulls, and they will scavenge as well as seek suitable small prey. They gather on landfills and a sharp increase in population is therefore considered as an indicator for a degraded environment. Kelp gulls have been observed feeding on live right whales since at least 1996. The kelp gull uses its powerful beak to peck down centimetres into the skin and blubber, often leaving the whales with large open sores, some of which have been observed to be half a meter in diameter. This predatory behavior has been documented in Argentinian waters, and continues today. At rocky sites along the southern African coast, such as at Boulders Beach in Cape Town, kelp gulls can be seen picking up shellfish and repeatedly flying up several meters and dropping them onto the rocks below in order to break them open. They have also been reported pecking the eyes out of seal pups on the coast of Namibia before attacking the blind seals in a group. The nest is a shallow depression on the ground lined with vegetation and feathers. The female usually lays 2 or 3 eggs. Both parents feed the young birds.
Gallery
Cape gull (''Larus dominicanus vetula'' or ''Larus vetula'')
The Cape gull differs from other forms of kelp gulls by its immaculate white tail and dark eye.
