Heermann’s Gull
Heermann's Gull
Larus heermanni
At a Glance
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.
All bird guide text and rangemaps adapted from Lives of North American Birds by Kenn Kaufman© 1996, used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Category
Gull-like Birds, Gulls and Terns
IUCN Status
Near Threatened
Habitat
Coasts and Shorelines, Lakes, Ponds, and Rivers, Open Ocean, Saltwater Wetlands
Region
California, Northwest, Southwest, Western Canada
Behavior
Direct Flight, Soaring
Population
350.000
Range & Identification
Migration & Range Maps
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.
Description
18-21" (46-53 cm). Adult has gray body, black tail, red bill. Head white in breeding plumage, mottled at other seasons. Immature smooth dark brown or gray-brown (without the heavy mottling of other dark young gulls); bill pinkish at base, legs black.
Size
About the size of a Crow, About the size of a Mallard or Herring Gull
Color
Black, Brown, Gray, Orange, Red, White
Wing Shape
Broad, Pointed
Tail Shape
Rounded, Short, Square-tipped
Songs and Calls
A high see-whee. Also a low-pitched kuk-kuk-kuk.
Call Pattern
Flat, Undulating
Call Type
Raucous, Scream
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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Behavior
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.
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.
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.
Climate Vulnerability
Conservation Status
Vulnerable to disturbance on main nesting islands in Mexico, where fishermen sometimes land to harvest eggs.
Climate Threats Facing the Heermann's Gull
Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.