This site, in Pacific County, comprises the mudflats and wetlands of the Willapa River estuary, extending from the two-meter elevation contour to the subtidal area of Willapa Bay. It includes the mouth of the Willapa River and Fredrickson, Johnson, and Mailboat Sloughs, but excludes the Willapa Harbor Airport and the developed areas around the city of South Bend.
Two-thirds of the IBA are intertidal mudflats, plus emergent wetlands in the upper reaches of the estuary, and some fresh water wetlands. The estuary is important primarily to wintering and migrating shorebirds, which feed on the mudflats, and roost in the marshes and pastures along the river. Dominant species are Western Sandpiper and Short-billed Dowitcher in spring, and Dunlin in winter. The site's secondary importance is as a fall migration and wintering site for waterfowl, mostly Brant, Canada Goose, Mallard, and American Wigeon. The wetlands near the airport are particularly valuable for waterfowl, and support breeding Wood Ducks. A mineral spring frequented by Band-tailed Pigeons is located on the north shore, about six kilometers downstream from the city of South Bend.
2013 Assessment based on BLM Oregon/Washington Surface Management Ownership dataset (http://www.blm.gov/or/gis/data-details.php?data=ds000011) and Washington Department of Natural Resources Aquatic Land Ownership Parcels (http://fortress.wa.gov/dnr/app1/dataweb/dmmatrix.html).