The Salton Sea, a globally significant Important Bird Area, is one of the most critical inland habitats for birds along the Pacific Flyway, and is now also one of the most imperiled. Best considered a branch of the larger Colorado River Delta, the sea formed and dried for eons prior to its most recent iteration, the result of a massive flood of irrigation water from the Colorado River just over 100 years ago. As a result, its avifauna is distinctly delta-like, dominated by fish-eating waterfowl and waders, from tiny Eared Grebes which winter by the thousands in rafts far out on its surface, to the American White Pelicans that roost on mudflats and fish for tilapia in its shallows.

The sea is also gravely threatened. Essentially since its inception, it has been getting saltier, and thus less suitable for fish (early introductions of both freshwater and Gulf of California species began to fail by the mid-1900s, and now tilapia are about all that’s left – and even these are apparently getting smaller and dying-off more frequently).

Water transfers approved in 2003 have promised that the abundant irrigation water from the Colorado River will instead be diverted (sold) to urban uses on the coast, particularly in San Diego County, and thus no longer available to the croplands of the sea, whose runoff has kept water levels more or less high and stable for the past 11 decades.

Obviously, this change will result in a more “natural” sea, one not dependent on canals and agricultural runoff, but the amount of water it will actually hold is not known. When the water transfers reach their predicted peak in 2017, both the natural runoff potential into the sea, as well as the anthropogenic/“human-assisted” sources that have been feeding it (and keeping the fishery, as well as the waterbird community, thriving), will be massively reduced.  

A handful of bird species are true “specialties” of the Salton Sea, barely reaching the U.S. from northwestern Mexico, such as the vanrossemi race of the Gull-billed Tern which breeds locally on islands at the south end of the sea and the rostratus race of the Savannah Sparrow, a true Delta endemic which breeds in desert wetlands at the head of the Gulf of California, and disperses north to the sea in fall.

But the sea is arguably most critical for the wintering and migratory species that spend anywhere from a few days to most of the year here. The numbers speak for themselves: 90% of the North American population of Eared Grebe may overwinter on the sea, along with up to 50% of the Pacific Flyway population of Ruddy Duck. 40% of the global population of the Federally Endangered Yuma Ridgway’s Rail (formerly Yuma clapper rail) occur in cattail marshes in the irrigation canals and natural rivers entering at the sea’s edge, and the sea is the primary wintering area in the interior U.S. for the both California Brown Pelican and American White Pelican, and Western Snowy Plover. Wintering populations of several more common waterbird species, such as Western Grebe, are likely the largest in the interior West, and the thousands of Cinnamon Teal, Black-necked Stilt, and other waterfowl and waders are unmatched in California south of San Francisco Bay. Many of these species feed on the abundant brine flies present year-round.

The sea is a destination for waterbirds from a very wide area, far beyond the borders of the state, and their use of sea changes through the year; thus, individuals of a single species, such as Clark’s Grebe, may occur at the sea as over-wintering birds, spring or fall migrants en route to and from pothole wetlands in the Great Basin, and local breeders at river mouths and sea-edge impoundments.

Several waders, including Great Blue Heron, have their largest nesting colonies in the state at the Salton Sea, where they utilize dead trees both on the sea and in flooded impoundments along its edges, and on the sea’s few islands, up to 25% of the breeding Caspian Terns in North America likely breed in some years, where they are joined by Double-crested Cormorants with some of the largest western U.S. breeding populations (waterbirds, particularly when nesting, are inherently variable, making generalizations about population representation difficult). It is this latter group – the breeding “inland seabirds” – that might be among the most imperiled as the sea shrinks. Over the past two years, their nesting islands have become connected with the shoreline, allowing predators to raid the nesting grounds of the cormorant and tern colonies, rendering them unusable. Recent proposals to pump water into nearby refuge impoundments to re-create nesting areas seek to maintain the sea’s importance to birds.

Here in 2015, one rather harsh reality about the Salton Sea appears to be certain, which is that the sea will continue to shrink, and become more saline as it does. This will eventually turn it into more of a hypersaline lake, too salty for anything but brine flies, so more like Mono Lake or Utah’s Great Salt Lake. A network of“off-sea” impoundments may ultimately replace the single massive body of water, and the sea itself may be simply an area to focus on dust-control measures, similar to the situation at Owens Lake (another inland water body that was quite different before the inputs were diverted).  

Prepared by Daniel S. Cooper, Cooper Ecological Monitoring, Inc., February 2015