Bryan Brillhart Photography Presents Dig Imperial Beach "Bird of the Week", the "Heermann's Gull "
Aug 04, 2016 06:21PM
By Paul Spear
Bryan Brillhart of Bryan Brillhart Photography presents us with the Dig Imperial Beach “Bird of the Week”. This week’s bird is the "Heermann's Gull (Larus heermanni)"
The column will provide a picture of a bird(s) locally photographed and we will have background on the bird.
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Heermann's Gull (Larus heermanni)
This week’s “Bird of the Week” is the Heermann's Gull (Larus heermanni), a gull resident in
the United States, Mexico, and extreme southwestern British Columbia.Nearly all of this species nests on Isla Rasa in the Gulf of California where they are vulnerable due to disturbance by fishermen who sometimes land to harvest their eggs. Isla Rasa was declared a sanctuary in 1964.
They are usually found near shores or well out to sea, very rarely inland. The species is named after Adolphus Lewis Heerman, a nineteenth-century explorer and naturalist,
look distinctly different from other gulls. Adults have a medium gray body, blackish-gray wings and tail with white edges, and a red bill with a black tip. The head is dusky gray in non-breeding plumage and white in breeding plumage. Juveniles resemble non-breeding adults but are darker and browner, and the bill is flesh-colored or pink till the second winter. A few birds, no more than 1 in 200, have white primary coverts, which form a showy spot on the upper wing. This gull is unlikely to be confused with other species as it is the only white-headed, gray-bodied gull found on the west coast of North America.
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.
Heermann’s gulls forage in flight over the sea, dipping to the surface or plunging into the water for fish. They pirate much food from other birds, stealing fish directly from the bill pouch of pelicans, and harassing other birds to force them to drop or disgorge their catch. They will also take eggs of other birds and will scavenge refuse or carrion, but they seem to do so less than some gulls.
Diet is fish and other small marine life. They eat many small fish, crustaceans, mollusks, and insects, and sometimes eat the eggs of other birds, refuse, or carrion.
Breeding behavior is not well known, but they nest during spring in colonies on islands off the west coast of Mexico. Some colonies very large, with only a few scattered nesting records on the U.S. coast. Nest sites are on level ground, usually in a colony on an island. Nests (probably built by both sexes) may be a shallow scrape in soil with very little lining, or a more substantial cup of grass and weeds, lined with feathers. Their nests are often at densities as high as 110 nests per 100 m2 (1,100 sq ft).
After mating, females lay 2-3, variable in color, pale gray to blue-gray, blotched with brown, lavender, and olive eggs. Incubation is by both sexes, probably in about 28 days. Adults incubate eggs in cool temperatures, shading them during day, since eggs could easily overheat in the intense sun of the hot desert islands where they nest. Young are fed by both parents. Age at first flight is not well known.
Look for this commonly seen gull along our awesome beaches while enjoying a walk at low tide. Until next week, happy birding!