The Elk River Estuary lies at the southernmost extension of marine waters in Gray's Harbor, about six kilometers southeast of Westport, and is the largest estuary in the south bay. This IBA includes the mouth of the Elk River, Beardsley Slough, Sopun Inlet, Mallard Slough and its adjacent uplands, and all the tidal marshes and mudflats south of the State Route 105 bridge. This is a pristine estuary, containing mudflats, both salt water and fresh water marshes, and marine waters. The state-owned portion of the site is a Natural Resources Conservation Area managed by the Department of Natural Resources (DNR).

Ownership State, county, private

Ornithological Summary

A 1993 report by DNR stated that the Elk River estuary is the largest, highest quality estuarine system remaining in Washington or Oregon. It includes diverse habitats, ranging from tideflats and sloughs, salt marsh and fresh water wetlands, to forested uplands. [It is] identified as critically important waterfowl and shorebird habitat.

The site's primary importance is as a fall migration area for waterfowl and a spring migration staging area for shorebirds. It is also a wintering area for Peregrine Falcons, and a small number of Trumpeter Swans and Brant; as well as breeding habitat for Bald Eagles, Pileated Woodpeckers, and Vaux's Swifts. Waterfowl are predominantly Mallard, American Wigeon, Green-winged Teal, and Northern Pintail. Data show that up to 15,000 shorebirds utilize the Elk River estuary to continue feeding on the rising tide when lower-lying sites in Gray's Harbor are flooded.

Conservation Issues

The Elk River Estuary is in a watershed used primarily for commercial forestry. Compared to other sites around Gray's harbor, residential development pressure is light, but is increasing. Runoff from adjacent agricultural lands and from the state highway create a minor risk of water pollution. Perhaps the greatest long-term threat is the possible invasion of the mudflats by Spartina, a non-native cordgrass.


2013 Assessment based on BLM Oregon/Washington Surface Management Ownership dataset ( and Washington Department of Natural Resources Aquatic Land Ownership Parcels (


Habitats Estuarine, salt marsh, coniferous forest

Land Use

Land Use Wildlife conservation, recreation, aquaculture

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