Part of a complex of closely related forms, it interbreeds freely with Western Gull at the southern end of its range, and often with Herring Gull and Glaucous Gull in Alaska.

It will also nest near colonies of California sea lions, scavenging any sea lion pups that die of natural causes. At the northern end of its range it hybridizes with Glaucous-winged Gull, and many ...

The most widespread pink-legged gull in North America, the herring is common in the east and mainly a winter visitor in the west. Hybrids can be locally common (mainly in the wescat). Polytypic.

The Iceland Gull is a medium-size gull, smaller than most Herring Gulls. It has a rounded head and smallish beak, giving it a dove-like expression. It has very pale plumage and white wing tips and, ...

The Glaucous Gull is a large pale gull with white wing tips. Younger birds are creamy white or more biscuit coloured, depending on age. All have pale wingtips. It's bigger than a Herring Gull and ...