The Great Black-backed Gull (Larus marinus) is the largest gull species in the world, with a length of 28-32 inches and a wingspan of 61-65 inches. This bird has a weight of around 3-5 pounds, with females being larger than males. Its distinguishing field marks include a black back, wings, and tail, with white on the head, neck, and underparts. The beak is yellow with a red spot, and the eyes are yellow.

The Great Black-backed Gull is a widespread species that breeds along the coasts of the North Atlantic, from eastern Canada to Greenland, Iceland, and northern Europe. During the non-breeding season, it can be found along the coasts of the northeastern United States, from Maine to Florida, and in the Gulf of Mexico. Some individuals may also winter in the Caribbean and on the coast of South America.

This species is a highly opportunistic predator, feeding on a wide variety of prey, including fish, crustaceans, mollusks, birds, and mammals. It is known for its aggressive behavior, often stealing food from other birds or scavenging from dead animals. The Great Black-backed Gull has also been observed attacking and killing other birds, including adult puffins and young gannets.

The breeding season for the Great Black-backed Gull begins in late April or early May, with pairs nesting on rocky cliffs or islands. The female lays 2-3 eggs, which are incubated for around 28-30 days. The chicks fledge at around 45-50 days old, but may continue to be cared for by their parents for several months.

Despite its large size, the Great Black-backed Gull is an impressive long-distance migrant, with some individuals traveling up to 3,000 miles between breeding and wintering grounds. In addition, this species has been known to wander far from its normal range, with sightings recorded as far inland as the Great Lakes region of North America. Overall, the Great Black-backed Gull is a fascinating and adaptable bird, well-suited to life in the harsh coastal environments of the North Atlantic.