Guide to North American Birds

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Photo: Jeff Poklen/Vireo

Heermann's Gull

Larus heermanni

Every summer, flocks of these distinctive gulls move north along the Pacific Coast from their nesting grounds in western Mexico. This movement is timed with the northward flight of Brown Pelicans; when a pelican comes to the surface after plunging into the water for fish, a Heermann's Gull is often waiting to try to snatch the fish from the pelican's pouch. Although this gull is not large, it is aggressive, harrying other birds to make them drop their catch.

Conservation status	Vulnerable to disturbance on main nesting islands in Mexico, where fishermen sometimes land to harvest eggs.
Family	Gulls and Terns
Habitat	Coast and nearby open ocean. Favors the immediate coast, including beaches, rocky shores, estuaries, coastal lagoons, offshore kelp beds. Unlike some other coastal gulls, seldom visits freshwater ponds or garbage dumps even a short distance inland. May occur far offshore, out of sight of land.

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Feeding Behavior

Forages in flight over sea, dipping to surface or plunging into water for fish. Pirates much food from other birds: steals fish directly from bill pouch of pelican, harasses other birds to force them to drop or disgorge their catch. Also will take eggs of other birds and will scavenge refuse or carrion, but seems to do so less than some gulls.

Eggs

2-3. Variable in color, pale gray to blue-gray, blotched with brown, lavender, olive. Incubation is by both sexes, probably about 28 days. Adults incubate eggs in cool temperatures, shade them during day; eggs could easily overheat in intense sun of hot desert islands. Young: Fed by both parents. Age at first flight not well known.

Young

Fed by both parents. Age at first flight not well known.

Diet

Fish and other small marine life. Eats many small fish, also crustaceans, mollusks, insects. Sometimes eats eggs of other birds, refuse, or carrion.

Nesting

Breeding behavior not well known. Nests during spring in colonies on islands off west coast of Mexico. Some colonies very large; only a few scattered nesting records on U.S. coast. Nest site is on level ground, usually in colony on island. Nest (probably built by both sexes) may be shallow scrape in soil with very little lining, or more substantial cup of grass and weeds, lined with feathers.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

Moves north along our Pacific Coast after nesting, first appearing in numbers in late May, remaining common until early February when most return to Mexico. Some may also disperse south of nesting areas along Mexican coast.