Heermann's Gull

Heermann's Gull is one of the most distinctive and unmistakable gulls in the world, with a sooty gray body found in no other North American gull species. Breeding adults have a crisp white head, a dark gray body and wings, and a striking red bill tipped with black, paired with black legs.

Outside the breeding season, the white head becomes streaked with gray. Juveniles are dark chocolate-brown overall, gradually lightening with age. This unusual coloration makes Heermann's Gull easy to pick out even at a distance among mixed flocks of paler gulls.

Remarkably, almost the entire world population breeds at a single site: Isla Rasa, a small island in Mexico's Gulf of California. After breeding, the birds disperse widely northward along the Pacific coast, reaching as far as British Columbia before returning south.

Key field marks

• Uniform dark slate-gray body, unique among North American gulls
• White head (breeding) becoming streaked gray in winter
• Bright red bill with a black tip
• Black legs
• Dark chocolate-brown juveniles

Similar species

• No other North American gull shares this combination of overall gray body and red bill, making Heermann's Gull essentially unmistakable once seen well; distant or backlit birds might suggest a dark immature gull of another species, but the red bill and uniform tone are diagnostic.

Habitat

A coastal species found on sandy beaches, rocky shorelines, harbors, and piers, rarely straying from the immediate coastline.

Range and migration

Nearly the entire breeding population nests on Isla Rasa in the Gulf of California, Mexico. After breeding, birds disperse north along the Pacific coast of North America, reaching British Columbia, before returning south to Mexico for the winter and following breeding season.

Behavior

Heermann's Gulls are notorious kleptoparasites, frequently harassing Brown Pelicans to steal fish as the pelicans surface from a plunge-dive, and also stealing food from other seabirds.

Voice

Calls include a distinctive, nasal, bugling note quite different from the calls of typical large gulls.

Feeding

Feeds on small fish, often obtained by piracy from pelicans, as well as by direct foraging and scavenging along beaches and harbors.

Nesting and breeding

Breeds in dense colonies, overwhelmingly concentrated at Isla Rasa, nesting on open ground among sparse vegetation. Clutches typically contain two to three eggs, incubated by both parents.