1, because the gulls to coastal insects, mollusks, crustaceans, and cultivated land worms and grubs for food, but also prey on the shore of small fish, picking up the shore and the ship discarded leftovers, so it is known as the "sea cleaner".

2, seagulls are birds, gull family of a medium-sized seabirds. Weight 394-586 grams; body length 451-510 mm. Lifespan 24 years. Adult summer plumage: head and neck white, back and shoulder slate gray; wing coverts also slate gray, same color as the back; waist, tail coverts and tail feathers are pure white. Primary flight feathers have white tips with large white wing mirrors. Scattered brown fine lines on head and neck in winter, sometimes with black at the tip of the beak. Iris yellow; beak, feet and toes light greenish-yellow.

3. Gulls are migratory birds. Breeding season mainly inhabits the Arctic tundra, forest tundra, deserts, grassland rivers, lakes, reservoirs and marshes, and in winter mainly inhabits the coast, estuaries and harbors. They move in pairs or small groups or fly in the air. On seashores and harbors, flocks float on the water's surface, swimming and foraging for food. Gulls feed on small seaside fish, insects, molluscs, crustaceans, and worms and grubs in cultivated fields.