Lewis & Clark National Wildlife Refuge
Pacific Region

Wildlife & Habitat

Lower Columbia River Estuary

Estuarine wetlands are some of the most productive environments on earth. The estuary supports abundant life because of the large expanses of shallow water, mud flats, and marshy and swampy islands. Fertile soil contributed by the river, nutrients and oxygen brought in by the tides, and sunlight combine to promote luxurious plant growth, ranging from plankton in the water to trees on the islands. Animals eat some of the vegetation but most of it eventually dies and decays. The decaying plant material feeds the estuary. Bits of decomposing plants become coated with bacteria and algae, and tides and currents carry these about. Small animals such as clams, worms, and young fish feed on this material. They in turn may be eaten by larger fish, seals, mammals or birds in a complex food web that also includes humans

The refuge encloses part of the largest marsh in western Oregon and is an important rearing area for anadromous fish. The array of fish in the lower Columbia River include coho and chinook salmon, sturgeon, and steelhead trout. The Lower Columbia River Fish Hatcheries maintain good health management and monitor the health of wild fish in the lower Columbia River.

Hundreds of fish and shellfish such as oysters, clams, shrimp, and salmon, live in estuaries at some point in their life. Estuaries protect water quality by filtering out sediment and pollution. In addition, estuaries, and the land surrounding them, are places where people live, sail, fish, swim, and bird watch. As a result, estuaries are often the centers of our coastal communities


This refuge encompasses more than 40% of the Columbia River estuary and includes numerous islands and bars, extensive mudflats, tidal marshes, and tidal swamps. The area is a major stopover for migratory waterfowl as they gather here before the northward migration. Peak populations of 500-1,000 tundra swans, 5,000 Canada geese, and 50,000 ducks arein February and March. Shorebird populations reach peaks of 150,000 birds. The refuge includes a large Caspian tern colony on Rice Island, and provides nesting areas for gulls, cormorants, and herons. The area is also used by peregrine falcons. Cathlamet Bay is the center of activity for wintering bald eagles on the Lower Columbia, and the area also supports a significant resident bald eagle population.

The estuary is both a migrational stopping place and a wintering area for waterfowl that nest in Alaska and winter in Oregon and California. The most common species are tundra swans, Canada geese, mallards, pintails, American wigeon, green-winged teal and greater scaup. Great blue herons, gulls and shorebirds wade the extensive sandbars and mud flats in search of small fish, insects, worms and crustaceans. Grebes and cormorants dive in the deeper water of the channels in search of fish. The willow, cottonwood and spruce trees of the vegetated islands provide nesting sites and lookout perches for numerous small birds, hawks and bald eagles.

For additional information, visit the Washington Audubon website.


Harbor seals use sandbars and mud flats as haul out sites at low tides, while both seals and California sea lions feed on a variety of fish in the estuary. Beaver, raccoon, weasel, opossum, mink, muskrat, coyote, and river otter live on the islands. Columbian white-tailed deer may be present on some of the upstream islands.

The Burke Museum at the University of Washington has a detailed list of mammals throughout Washington State. Research projects on marine mammals can be found at the National Marine Mammal Laboratory with particular attention to issues related to marine mammals located in waters near Alaska, Washington, Oregon, and California.

Reptiles and Amphibians

Lewis and Clark Wildlife Refuge has several reptiles and amphibians that are found throughout the Pacific Northwest. A few of these include red-legged frogs, common gartersnakes, and northwestern salamanders. The rough-skinned newt also inhabits the islands. Many newts produce toxins to avoid predation, but the toxins of rough-skinned newt is particularly potent.

For distribution maps and information on species of amphibians and reptiles, visit the Burke Museum Herpetology website.


The estuary is home to many species of fish. Fish use the estuary for spawning, feeding, and as a passageway between the ocean and the upper river. The estuary is particularly important as a feeding area for juvenile salmon while they go through the physical changes that allow them to survive in salt water. The salmon then migrate into the ocean where they grow to adulthood and live for several years. As adults, they return through the estuary, seeking out their natal streams upriver to spawn the next generation. Major sport and commercial fish species include coho, chum and Chinook salmon; steelhead and cutthroat trout; and white sturgeon.

Other fish using the estuary include American shad, smelt, starry flounder, and Pacific lamprey

Last updated: December 1, 2011