Threatened and Endangered Species - Status Reports
Date Published: July 1993
Number of Pages: 38
The Washington, Oregon, and California population of the marbled murrelet (Brachyramphus marmoratus marmoratus) was federally listed as a threatened species by the U.S. Fish and Wildlife Service on 28 September 1992. The main cause of the population decline and the primary threat to the marbled murrelet in the three-state area is the loss and alteration of nesting habitat, older forests, as a result of commercial timber harvesting. Additional lesser threats are mortality associated with gill-net fishing operations off the Washington coast, predation, urbanization, and the effects of oil spills.
The North American subspecies of the marbled murrelet is a small seabird of the Alcidae family which ranges from Alaska to central California. In Washington it is found in all nearshore marine areas (within 2 km, 1.2 mi of shoreline), with the greatest concentrations in northern Puget Sound.
Marbled murrelets are usually found within or adjacent to the marine environment where they feed primarily on fish and invertebrates. They spend the majority of their lives on salt water, but fly inland to nest. Most marine concentrations are in areas where older forests are present nearby. While marbled murrelets have been recorded up to 83 km (52 mil inland in Washington, the majority of observations are within 63 km (39 mil of the coast in the northern Washington Cascades. Marbled murrelets in Washington, Oregon, and California nest in older forests and are solitary to semi-colonial in nesting habit. Of 16 tree nests characterized (5 in Washington, 7 in Oregon, 4 in California), all were located in old-growth trees. The broad, horizontal limbs of older trees are generally needed to support the single murrelet egg which is laid on the limb , without benefit of a constructed nest. However, limb deformities sometimes serve as platforms.
Currently, marbled murrelet populations are estimated at no more than 5,000 birds in Washington, fewer than 1,000 pairs in Oregon, and about 2,000 birds in California. Anecdotal accounts suggest greater numbers historically, particularly in areas where timber harvest has been most extensive.
The quantity of old-growth forest in western Oregon and Washington has been reduced by more than 80% from pre-logging level s. In northwestern California, estimates put the reduction at 45-80%. Forest fragments are less suitable for successful nesting due to losses from excessive wind at stand edges, as well as increased predation, primarily by corvids (jays, ravens, and crows).
In Washington, the factors that contribute to the marbled murrelet's listing under the Endangered Species Act are expected to affect the species through the foreseeable future.
It is recommended that the marbled murrelet be designated as a threatened species in Washington.
Washington Department of Wildlife. 1993. Status of the marbled murrelet (Brachyramphus marmoratus) in Washington. Unpubl. Rep. Wash. Dept. Wildl., Olympia.