Lacustrine Habitat

1908 Finley and Bohlman photo of a pelican taking off from Malheur Lake

Thousands of floating islands between which flow narrow channels that are endless in their windings. The main body of the lake is still a mile beyond the place where the spring branch enters the tule jungle. The tules grow from eight to twelve feet high, so that when one enters the mass, he has no landmarks, unless, perchance, he can read signs in the heavens above.

 ~ William L. Finley's account of Malheur Lake in 1908 
from "Trail of the Plume Hunter" 1910 

One of the largest inland marshes in the United States, Malheur and Mud Lakes vary dramatically in size (from 500 to 110,000 acres), but generally fluctuate about 2 feet during the calendar year and on average cover 40,000 acres. Malheur Lake receives water from the Blitzen and Silvies rivers, fills from the center, then flows east and finally to the west, where it connects with Mud Lake. Water supply is predominantly influenced by snowpack on Steens Mountain to the south and intermittently by the Blue Mountains to the north.

The western section of Malheur Lake, including Mud Lake, is a series of natural ponds separated by a network of low dune islands and peninsulas. The center section, the deepest area of the lake, is predominantly open water with some hardstem bulrush stands near the mouth of tributaries. The eastern section tends to be more alkaline and lacks tall emergent vegetation.

Common emergent species in Malheur and Mud Lakes include hardstem bulrush, cattail, burreed, Baltic rush, and various sedges. The lakes contain extensive areas of open, aquatic bed habitat supporting submergent plants such as sago pondweed, water milfoil, horned pondweed, coontail, small and leafy pondweed, white water buttercup, bladderwort, and widgeon grass.

The primary wildlife value of the lakes includes their importance as foraging sites for migrating waterfowl, waterbirds, and shorebirds and as nesting habitat for colonial nesting waterbirds and diving ducks. Canvasbacks and tundra swans are particularly abundant when sago pondweed is abundant in the lakes, and many other dabbling and diving ducks are also supported in large numbers. Very high numbers of nesting colonial birds use the lake when habitat conditions are favorable, including white-faced ibis; American white pelican; great and snowy egrets; herons; Franklin’s, California, and ring-billed gulls; Caspian and Forster’s terns; and western, Clark’s, and eared grebes. Total colonial waterbird nests have at times exceeded 10,000 when the lakes reach optimal conditions. Migrant shorebirds use the lakes extensively, when natural fluctuating water cycles expose mudflats. The lakes are also very important to molting geese and ducks as the expansive open water provides them security from predators.

The large invasive carp population in Malheur and Mud lakes and in the Blitzen and Silvies rivers has severely compromised submerged aquatic vegetation (e.g., sago pondweed); therefore, the lakes do not adequately support refuge purposes. Historically, Malheur Lake was a key staging area for canvasbacks and tundra swans in the Pacific Flyway. As a consequence of declining habitat quality, these and other waterfowl no longer stage in significant numbers on the lake except during years following major carp control efforts. Waterfowl production is less than 10 percent of its potential on the lakes because of carp.