Human-induced changes in the Columbia River Basin appear to have facilitated increases in populations of colonial waterbirds such as Caspian terns (Sterna caspia). The numbers of Caspian terns in western North America more than doubled between 1980 and 1999. One reason for the increase is that human-created habitat provides high-quality nest sites and is associated with population increases in many parts of North America.

There were no recorded observations of terns nesting in the Columbia River estuary before 1984, when approximately 1,000 pairs apparently moved from Willapa Bay to nest on newly deposited dredge material on East Sand Island. In 1986, those birds moved to Rice Island, created by the Army Corps of Engineers for dredge disposal. The Caspian tern colonies in the estuary then expanded to 9,000-10,000 pairs, the largest ever reported. In 1999, the colony was encouraged to relocate to East Sand Island. In 2001, the majority of the West Coast population nested on just four acres on East Sand Island; in 2002, the terns nested on six acres. There, the terns feed on large numbers of migrating juvenile salmon and steelhead. Basin-wide losses to avian predators now constitute a substantial proportion of individual ESA-listed salmonid runs.