Aquatic and terrestrial insects, earthworms, and marine invertebrates compose the bulk of L. ridibundus diet. This species also feeds on fish and grains, although to a lesser extent. Studies have shown that adults store greater nutrient reserves (fat and protein depots) not only for migration, but for reproductive activity as well.
This species forages by swimming and snatching food from the water surface, or by submerging its head under the water surface. These birds forage along coastal areas. Adults have more efficient foraging skills than do immature birds. Due to this inefficiency, immature birds feed in areas separate from the adult sites. Immature birds also display greater aggression, often winning fights over food. Interestingly, they are also more brazen in approaching humans, thus gaining a better chance to secure food.
The gulls are also kleptoparasitic on occasion, meaning that they steal food that has already been caught by a member of the same or different species. For example, in the Netherlands, sandwich terns (Sterna sandvicensis) nearly always stake their breeding ground in close proximity to colonies of L. ridibundus. In this arrangement, the gulls help protect the terns by driving out both avian and ground predators. The gulls, though, are major predators of tern eggs and chicks, and steal fish that tern parents have procured for their chicks. Larus ridibundus prefers to eat tern chicks up to two weeks old. Several scientists have suggested that kleptoparasitism occurs more often when other food sources are scarce.
Larus ridibundus displays high flexibility in diet. In western Europe, for instance, it has come to rely on human trash as an artificial food source. Researchers have attributed the significant increase in distribution of L. ridibundus to this influx of readily available food (Howard and Moore, 1991; Cantos et al., 1994; Stienen and Brenninkmeijer, 1999; Nuyts et al., 1996).
Animal Foods: birds; fish; eggs
Primary Diet: carnivore (Piscivore )