Heermann's Gull

Overview

Heermann's Gull is a medium-sized gull of the Pacific coast of North America, notable for its unusually dark, uniformly sooty-gray body plumage, a pattern shared by few other gulls in the region. Breeding adults combine this dark body with a clean white head and a bright red bill tipped in black, an eye-catching combination among the paler gulls typically seen along the same coastline. The tail is blackish with a narrow white terminal band, adding to its distinctive silhouette in flight.

Most of the world's population breeds on a single island in the Gulf of California, after which birds disperse widely northward along the Pacific coast for the nonbreeding season, making it a familiar sight on beaches and harbors from Mexico to British Columbia outside the breeding period.

Feather Identification

• Wing feathers: Both flight feathers and coverts are a uniform dark slate-gray to sooty brown-gray, lacking the pale gray tones typical of most gulls, giving the whole wing an unusually dark, blended appearance with little contrast between coverts and flight feathers.
• Tail feathers: Blackish with a narrow white tip, contrasting with the dark rump and back.
• Size and shape: Flight feathers are moderately broad, matching a stocky, medium-large gull body.
• Head and body feathers: Breeding adults show a crisp white head sharply demarcated from the dark gray body, while nonbreeding adults show a duskier, mottled head that blends more with the body tone.
• Compared to similar species: No other regularly occurring Pacific coast gull shows this combination of uniformly dark body plumage and a white or mottled head; darker juvenile gulls of other species are typically browner and more mottled rather than uniformly sooty-gray.

Plumage Details

Breeding adults show a clean white head, dark slate-gray body and wings, a blackish tail with a white tip, and a bright red bill with a black tip. In nonbreeding plumage the head becomes mottled gray-brown, blending more with the body color, and the bill often dulls slightly. Juveniles are an overall dark sooty brown, including the head, with a dark bill, gradually lightening on the head and developing the adult's gray body tone over a few years, with full adult plumage attained by around the third or fourth year.

Habitat & Range

The great majority of Heermann's Gulls breed on Isla Rasa in the Gulf of California, Mexico, with a few smaller colonies elsewhere along the Mexican Pacific coast. After breeding, the population disperses widely northward along the Pacific coast of North America, becoming common on beaches, jetties, and harbors from Mexico north through California and occasionally as far as British Columbia, before returning south to breed. It is essentially absent from the interior and rarely strays far from the immediate coastline.

Behavior & Field Notes

Heermann's Gulls are notable kleptoparasites, frequently chasing and harassing Brown Pelicans and other seabirds to steal captured fish, in addition to foraging independently along the shoreline and taking discarded bait and fish scraps around harbors. They breed in dense colonies, nesting on the ground with minimal structure, heavily concentrated on a very small number of island sites. The call is a nasal, grating note typical of Larus gulls. Its dark, uniform plumage combined with the white head in breeding season and its habit of following pelicans make it one of the more readily identifiable gulls along the Pacific coast.