Immature (2nd winter)
  • Immature (2nd winter)

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Slaty-backed Gull

Larus schistisagus
This is a large and highly varied group of birds that do not have many outward similarities. Most are water birds that feed on invertebrates or small aquatic creatures. The order is well represented in Washington, with seven families:
The family Laridae is made up of birds closely associated with water. Distributed throughout the world, representatives of this family nest on every continent, including Antarctica. Most are long-lived birds, many of which do not breed until they are three or four years old. Most are colony nesters and nest on the ground. Clutch size is generally small, varying from one to four eggs. Both parents incubate the eggs and help feed the young. The young typically hatch covered with down and stay in the nest for a few days, after which they leave the nest but stay nearby. Most, especially in Washington, raise a single brood a year. This group is known for its elaborate displays in the air and on the ground.

The Washington representatives of this family can be split into two groups, or subfamilies. The adaptable gulls are the most familiar. Sociable in all seasons, they are mainly coastal, but a number of species also nest inland. Many—but not all—are found around people. Gulls have highly variable foraging techniques and diets. Terns forage in flight, swooping to catch fish or insects. They dive headfirst into the water for fish. Although they are likely to be near water, they spend less time swimming than gulls.

    General Description

    This rare winter visitor is the same size as the Western Gull, which it also resembles in structure and general appearance. The adult has pink legs and a mantle a shade darker than our local race of Western Gull’s, although mantle color can be tricky to judge under field conditions. The head, neck, and upper breast are streaked in winter, whereas those of the Western Gull remain immaculate white (but beware of Western Gull x Glaucous-winged Gull hybrids, common in western Washington, which may have variable amounts of streaking in winter plumage). The eye of the adult Slaty-backed is usually but not always pale, rather like Herring Gull’s, while that of our northern race of Western Gull is usually but not always dark. In flight, the adult Slaty-backed shows less black, and more white, in the wingtips than Western and a relatively broader white trailing edge of the wing. [N.B.: The above descriptions are oversimplified. Field guides should be consulted—even more so for the immature plumages of the first three years of the bird’s life.]

    A coastal resident of the northwest Pacific, the Slaty-backed Gull breeds from Siberia to northern Japan and winters from Japan south to Taiwan and east through the Bering Sea region to Alaska. Small numbers have bred in Alaska in recent years, and the species now shows up regularly in winter farther south along the West Coast. Washington’s first record was in 1986. The state now has 10 accepted records between mid-December and mid-March. All are from the Puget Lowlands, often at river mouths. Oregon has several records along the lower Columbia River, and Slaty-backed Gull is now annual in British Columbia.

    Revised June 2007

    Federal Endangered Species ListAudubon/American Bird Conservancy Watch ListState Endangered Species ListAudubon Washington Vulnerable Birds List

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