The Kelp Gull, Larus dominicanus, is a large seabird found across much of the Southern Hemisphere. This adaptable species is known for its opportunistic feeding habits and broad distribution in diverse coastal environments. It is often seen along shorelines and near human settlements where food is plentiful.
Identification and Distribution
Adult Kelp Gulls display a distinctive appearance, featuring a bright white head, neck, underparts, and tail, contrasted by a black back and wings. Their wingtips often show small white patches, sometimes described as “mirrors”. The bill is yellow with a noticeable red spot on the lower mandible, and their legs are typically greenish-yellow, becoming more vibrant during the breeding season. This species measures between 54 and 65 centimeters in length, with a wingspan ranging from 128 to 142 centimeters.
Juvenile Kelp Gulls appear quite different, with mottled brown plumage and a dark bill, gradually acquiring adult coloration over three to four years. The Kelp Gull’s range is circumpolar across the Southern Hemisphere, encompassing the coasts of South America, Southern Africa, Australia, and New Zealand, where it is often called the Southern Black-backed Gull. It also inhabits subantarctic islands and the Antarctic Peninsula.
Diet and Foraging Habits
Kelp Gulls are opportunistic omnivores. They scavenge extensively at human-modified sites such as landfills, harbors, and fishing operations, which has contributed to population increases in some areas. Their natural diet includes a wide array of aquatic prey like fish, mollusks, worms, echinoderms, and arthropods.
These gulls also prey on eggs and chicks of other seabirds, including African Penguins and cormorants. A notable foraging behavior involves picking up hard-shelled mollusks, such as mussels, flying several meters high, and dropping them onto hard surfaces like rocks, roads, or jetties to break them open. This learned technique allows them to access the soft body inside the shell.
Unique Predatory Behaviors
A unique predatory behavior has emerged in some Kelp Gull populations, especially off Argentina’s Valdés Peninsula. Gulls have learned to land on the backs of living southern right whales to tear off pieces of skin and blubber with their powerful beaks. This behavior, first reported in the 1970s, has become more frequent, with the percentage of whales bearing gull-inflicted wounds increasing from 2% in the 1970s to 99% by the 2000s.
These attacks create large, open sores, which can lead to infection, dehydration, and thermoregulation problems for the whales. Whales respond to these attacks with costly movements, and mothers have developed behaviors such as the “oblique breathing” posture to keep their backs submerged. This constant harassment forces whales to expend energy, potentially contributing to increased calf mortality observed in the region. The gulls often target pre-existing wounds, and calves, being less experienced and spending more time at the surface, are particularly vulnerable.
Nesting and Reproduction
Kelp Gulls are monogamous and often breed in colonies, though solitary nests occur. Their breeding season varies geographically but generally occurs between September and January in the Southern Hemisphere. Nests are shallow depressions on the ground, lined with vegetation. These nests are commonly found on coastal islands, beaches, cliffs, or in urban areas.
A typical clutch consists of two to three eggs, though some populations may lay up to four. Both parents share the duties of incubating the eggs, which takes approximately 26 to 27 days. Chicks are semi-precocial, meaning they can leave the nest within hours of hatching, but remain dependent on their parents for food for about 12 weeks.