The Tulare Basin is located in the southern most end of California's Central Valley. Historically, the Basin contained the largest contiguous freshwater wetland west of the Mississippi. In heavy rainfall years, the Basin would swell and cover more than 500,000 acres, creating a vast expanse of shallow seasonal and deeper perennial wetland habitats. This landscape lured waterfowl, shorebirds, and waterbirds by the millions. The Tulare Basin radically transformed in the late 19th century when agriculture came to the Valley and began to divert water from the Basin's tributaries. Levee construction and water diversions confined and eventually reduced the wetland habitat to less that 15,000 acres.
Since the natural hydrology of the Basin has been all but eliminated, wetland habitat must now be maintained with artificial water supplies that are increasingly expensive. Because of this and other factors, the number and acreage of privately owned and managed wetlands continues to dwindle, further comprising the habit and the birds that depend upon it.