The biggest seagull species is the great black backed gull, Larus marinus. They can grow to lengths of 64 to 79 centimeters, or 25 to 31 inches, with a wingspan of 1.5 to 1.7 meters, or 4.11 to 5.7 feet. They usually weigh between 0.75 and 2.3 kilograms, or 1.7 and 5.1 pounds.
They have a very strong societal structure that works well on keeping predators away from their breeding grounds. If they see a predator lurking by, up to a hundred gulls will form up to drive the predator away, sometimes even driving them out to sea to drown.
Seagulls are omnivores, which means that their diet is both plant and meat based. Their diet consists of fish, marine and freshwater invertebrates, terrestrial arthropods, insects, earthworms, rodents, eggs, carrion, offal, reptiles, amphibians, seeds, fruit, human refuse, chips and other birds.
Seagulls are relatively intelligent birds. For example, they have been seen using strategy to find ways to seal food from other animals and eve humans. They have also been found to fly up in the air and drop hard shelled fish so that they could crack the shell and eat the soft meat inside.