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Larus heermanni - Heermann’s Gull

Heermann’s Gull image

Geographic range:

Eastern Pacific from British Columbia to central Mexico

Key features:

Medium sized gull, bright red bill with black tip, dark gray plumage, black legs and feet, black tail with white terminal band, and white head in breeding plumage

Similar species:

Larus californicus -- California Gull

Habitat(s):

bay (rocky shore), bay (sandy shore), Continental shelf, exposed sandy beaches, pelagic zone, protected sandy beaches
 

Primary common name:

Heermann’s Gull

General grouping:

Seabirds and shorebirds

ITIS code:

 

Geographic Range

Range Description:

Heerman’s Gull winters along the eastern Pacific, extending northward to British Columbia and just south of Baja California, both on islands in the Gulf of California and on the mainland.

Habitats

bay (rocky shore), bay (sandy shore), Continental shelf, exposed sandy beaches, pelagic zone, protected sandy beaches

Habitat notes:

Coastal species, occur on sandy beaches and nearshore waters.

Abundance

Relative abundance:

Common in summer, but also present in fall and winter along the central California coast

Species Description

General description:

The Heermann’s Gull is in the Family Laridae, which includes Skuas, Jaegers, Gulls, and Terns. It is a beautiful, medium sized gull, strikingly marked and hard to confuse with any other gull due to its dark coloration. Breeding adults have light gray underparts, dark gray upperparts, a white head, black legs and feet, broad and pointed wings with a trailing white edge, black tail with a white terminal band, black eyes, and a bright red, 2 inch (5 cm) long bill with a black tip. Its flight has been described as “buoyant”.

In non-breeding plumage the head is dusky gray and the body is dark. The male is slightly larger than the female. Gulls require 2-5 years to reach adult plumage. The Heermann’s Gull is often considered to be a “three year” gull, meaning it takes three years for a Heermann’s to attain adult plumage. In its first winter it is uniformly sooty brown all over. The bill is two-toned, with a pale flesh colored base and a black tip. The eyes are dark, legs and feet black; wing feathers and tail are also black.

In its second winter the body becomes sooty gray and the head and neck become slate black. The dark eyes develop white crescents above and below. The wing feathers develop white tips and the tail has a white band at the tip. The bill is now red with a black tip. In the second summer the head develops a whitish hood. And by the next spring full adult plumage is achieved.

Heermann’s Gulls are usually quiet when away from breeding grounds. However on their breeding islands in the Gulf of California, nesting in large colonies of up to 200,000 pairs, the noise is significant. Their voice is described as a deep “Kwak” and a high pitched “weee” or “aow, aow”, nasal and whiny, with a different quality than other gulls. A group of gulls may be called the following: a flotilla, gullery, screech, scavenging, or squabble of gulls.

Distinctive features:

Dark gray, medium-sized body, white head, and red bill tipped with black

Size:

Length: 45-53 cm (18-21 in) Wingspan: 104-115 cm (41-45 in) Weight: 371-643 g (13.1 – 22.7 oz)

Natural History

General natural history:

The Heermann’s Gull is named after Dr. Aldolphus Heermann, a surgeon and naturalist, on a U.S. survey team in the West in the 1850’s. It is North America’s only gull to breed (March to June) south of the United States and then come north for the non-breeding season. (A small number will go south to Guatemala after breeding.) Once breeding is completed on arid islands in the Gulf of California, Mexico, they fly north, some as far as British Columbia. Although they can be found both near shore or well out to sea, they are primarily coastal birds, choosing beaches, rocky shorelines, small offshore islands, estuaries, kelp beds, and lagoons as roosting sites. They rarely venture inland, although it is considered a rare non-breeder at the Salton Sea, California, where it is seen most often in July.

This gull is known to be quite aggressive and can be seen harassing other birds to make them drop food items, especially the Brown Pelican (Pelecanus occidentalis). At times they actually steal fish directly from the pouch of a pelican. An adult Heermann’s Gull is most likely to steal food from an adult pelican, and an immature Heermann’s Gull is more likely to steal from an immature pelican. Interestingly the post-breeding dispersal of Heermann’s Gulls coincides with the northward movement of Brown Pelicans. They also chase and kleptoparasitize Elegant and Royal Terns (Sterna spp.), cormorants (Phalacrocorax spp.), boobies ( Sula spp.), Ringed Kingfishers (Ceryle torquata), Bonaparte’s Gulls (Larus philadelphia). They also hover and dip to pick food from the surface of the water, or forage for small fish, such as Pacific sardines (Sardinops sagax caeruleus), herring (Clupeidae spp), and anchovies (Engraulidae spp), plunging into the water in pursuit if it is near the surface. They will also scavenge lizards, insects, crustaceans, mollusks, and other marine organisms from beaches, kelp beds, and fishing boat dumps. Eggs, other birds, garbage, and carrion are also eaten.

Predator(s):

Common Raven (Corvus corax ), black rat (Rattus rattus), Yellow-footed Gull, and Peregrine Falcon (Falco peregrinus)

Prey:

Smelt, herring, anchovies, sardines, lizards, insects, crustaceans, mollusks, other marine organisms, bird eggs, other birds, garbage, and carrion

Feeding behavior

Carnivore, Omnivore, Scavenger

Feeding behavior notes:

Although some individuals feed along beaches, sheltered bays and harbors, rocky promontories, and kelp beds, the majority are maritime and pursue schools of herring and other small fish, some kilometers offshore. They often join mixed-species assemblages of feeding cormorants (Phalacrocorax spp.), boobies (Sula spp.), and pelicans (Pelecanus spp.). Foraging methods in California include picking up food from the ground and water surface. To obtain food below water while swimming, they jump up and then dive down into the water to secure the prey. When flying, they plunge into the water in pursuit of fish.

In August, along the Pacific Northwest coast, they often hover over breakers to catch smelt from the crests of waves as these fish head to spawn along beaches. When herring swim in schools near the surface, the Heermann’s Gulls fly to the school from behind, making quick, repeated dips into the school. As soon as herring return to the surface after the initial attack, these gulls make a wide circuit and return to pursue the school again from behind.

In addition, Heermann’s Gulls actively pursue a wide range of birds, including Blue-footed Booby (Sula nebouxii), Ringed Kingfisher (Ceryle torquata), Bonaparte’s Gull (Larus philadelphia), and Elegant and Royal Terns (Sterna spp.), much like a Jaeger does, attempting to pirate their catches. Brown Pelicans are most often kleptoparasitized. Heermann’s Gulls initiate a kleptoparasitic attempt by flying directly toward a diving pelican. After the pelican plunge-dives and bobs to the surface with its prey, the gulls position on either side of the pelican and attempt to dislodge the fish directly from its gular pouch. They also kleptoparasitize feeding California sea lions (Zalophus californianus) by seizing scraps of fish from their mouths.

As with most medium-sized gulls, they drink both salt water and fresh water by dipping their bill into water and lifting their head to swallow. Excessive salt is excreted from nasal glands into the nostrils (nares) on the cere (top of the bill) from which it drips.

December - February

Migration:

By December most adult Hermann’s Gulls begin to head to their breeding grounds on arid islands in the Gulf of California. They travel short-distances as they migrate and often do not arrive at their breeding grounds until late February or early March. Although this gull roosts in large flocks, they are rarely seen flying in large flocks. Some sub-adults remain in their non-breeding range year round.

March - May

Reproduction:

Heermann’s Gull breeds primarily on arid islands in the Gulf of California, Mexico. Isla Raza, a small 150-acre island in the Gulf of California, accounts for 90-95% of the total world breeding population. The island was protected by Mexico in 1964 to discourage the collection of the gulls’ eggs. This 150 acre volcanic island contains rocky hills, mostly covered with a substrate of small rocks, and valleys filled with guano. Vegetation is scarce. Other islands that Mexico has declared “Important Bird Areas”, which are now protected, are Isla Benitos and Isla Angel de la Guarda. Other nesting-island locations in the Gulf of California include San Ildefonso, George, Cholluda, Partida, Cardinosa, Salsipuedes, and Monserrate.

Upon arriving at their Sea of Cortez arid breeding island, courtship begins. Large flocks on Isla Raza gather at dusk to roost at their breeding colonies but depart at dawn. During this period, they are intensely involved in courtship and territorial displays that result in pair formation. During courtship displays, the male flies over the sitting female. She solicits the male by squatting and emitting squeaky call notes. They also lock bills and pull one another, as if dancing, before disengaging bills and moving apart; vocalizations accompany all stages of this behavior. The pair is monogamous. They gather at dusk to roost but depart at dawn to feed off shore. By late March or early April large colonies have formed, often mixed with Elegant (Sterna elegans) and Royal Terns (S. maxima ). Nests are prepared (either a simple scrape in the soil or an open platform of sticks, grass, and weeds among boulders or a clump of grass). Two to three ovoid grayish cream colored eggs, marked with lavender/brown/blue, are laid. Both parents incubate the eggs, providing shade to keep the eggs from overheating. They guard the nest aggressively and if it is even partially destroyed they will desert the nest and eggs. The eggs hatch in approximately 28 days. If a third egg hatches the chick usually does not survive. The chicks are semiprecocial, with eyes open. The down on their back is grayish white, mottled with dusky gray; the head, throat, breast, and flanks are a pinkish buff. Belly down is white. The head has a few dusky spots. Both parents guard them and try to chase them back to the nest if they wander away. Both parents feed their young. Chicks beg for food from their parents while they are on their breeding grounds. If there is a food shortage parents will only feed the first-hatched chick. The young fledge in about 45 days. By June most Heermann’s Gulls are ready to migrate to their non-breeding territories, where they remain until December. The majority of the population disperses and winters north of their breeding range. Chicks that survive until adulthood begin to breed at three or four years of age.

Feeding:

At breeding colonies, the Heermann’s Gull preys on eggs of Elegant (Sterna elegans) and Royal (S. maxima) Terns; also eggs of other gulls, including Heermann’s Gulls. They also scavenge with other gulls along the rocky and intertidal shoreline and beaches for mollusks, crustaceans, lizards, insects, refuse and carrion. Nearshore kelp beds are also a favored feeding territory.

May - June

Migration:

Early breeders and their young are ready to fly to their non-breeding grounds and early as May. Later breeders may not depart until June. Most fly northward, some going as far as British Columbia. A few head south to Guatemala.

In the central California area some Heermann’s Gulls begin arriving by mid-June. Arriving gulls continue to increase until an estimated 60,000 have arrived by mid-July. Their migration is made flying many short stretches taking until July or August to reach British Columbia.

June - December

Feeding:

Although some individuals feed along beaches, sheltered bays and harbors, rocky promontories, and kelp beds, the majority are maritime and pursue schools of herring and other small fish, some kilometers offshore. They often feed in mixed flocks with other gulls, cormorants and pelicans. They will kleptoparasitize any of these fellow feeders with aggressive pursuit. In August, along the coast of the Pacific Northwest, they often hover over breakers to catch smelt from the crests of waves as these fish head to spawn along beaches.

Monterey Bay National Marine Sanctuary:

Main threats to Heermann’s Gulls occur on their nesting grounds, including: harvesting of their eggs; nest predation by introduced mammals, such as black rats (Rattus rattus) that eat the eggs and chicks; industrial development for guano extraction; and tourism. Other recent threats include oil spills, accumulation of high levels of pesticide contaminants in body tissues from their diet, and direct competition with humans for Pacific sardines (Sardinops sagax caeruleus).

The effects of weather on their prey species can also produce great fluctuations in annual breeding success. For these reasons the IUCN includes the Heermann’s Gull on its Red List and its status is currently “Near Threatened”.
Click on an image below to view a larger version in the SIMoN Photo Library. You will also be able to view important information on each photo such as photographer, date, caption and more.
Ehrlich, P., D.S. Dobkin, and D. Wheye. 1988. The Birders Handbook: A Field Guide to the Natural History of North American Birds. Simon & Schuster Inc., New York. 785 p.
NOAA. 1994. Beached marine birds and mammals of the North American West Coast: a revised guide to their identification. NOAA Sanctuaries and Reserves Division, U.S. Department of Commerce
Roberson, D. 2002. Monterey Birds 2nd edition. Monterey Peninsula Audubon Society, Carmel, CA. 536 p.
Sibley, D.A. 2000. The Sibley Guide to Bird. Alfred A. Knopf, Inc. 545 p.
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About.Com
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http://birding.about.com/od/birdprofiles/p/killdeer.htm

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Alaska SeaLife Center
http://www.alaskasealife.org

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Arkive
Images of Life on Earth. 2009. Heermann’ gull, Larus heermanni
http://www.arkive.org/heermanns-gull/larus-heermanni/biology.html
http://www.arkive.org/sooty-shearwater/puffinus-griseus/#text=Description

WWW
Cornell Lab of Ornithology
All About Birds
http://www.allaboutbirds.org/guide/search

WWW
Ocean Oasis Field Guide. 2000. San Diego Natural History Museum & PRONATURA
http://www.oceanoasis.org/fieldguide/
Accessed 04/13/09 for Heermann’s Gull
http://www.sdnhm.org/ge_files/pdf/Heermann's%20Gull.pdf

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Seattle Audubon Society.
http://www.seattleaudubon.org/birdweb/

WWW
Suddjian, David. 2000. Identifying Gulls. Santa Cruz Bird Club.
http://santacruzbirdclub.org/gullint.html

WWW
WhatBird.com. Field Guide to Birds of North America.
http://www.whatbird.com