The Imperial Valley, located in extreme southeastern California between the Salton Sea and the U.S.-Mexico border, is one of the premiere winter birding spots in the country. Most of the wetland habitat is contained within units of the Sonny Bono Salton Sea National Wildlife Refuge and the Imperial State Wildlife Area (including Finney-Ramer Lakes), as well as a handful of private duck clubs. The refuges also contain large fields of grains adjacent to marshes, similar to those hundreds of miles northwest in California's Central Valley. Limited wetland and riparian (mainly tamarisk) vegetation is also associated with the two main rivers, the New and the Alamo, that flow north across the valley into to Sea. Both rivers are fed nearly exclusively by agricultural runoff, a situation that has been implicated in massive die-offs of birds at the Salton Sea. A mosaic of irregularly-flooded row crops, irrigation canals, and occasional remnants of native alkali sink scrub also contribute to the area's staggering number and diversity of bird species nearly year round. The Imperial Valley is also one of the most important agricultural areas of the state, and its farmland extends south from the international border nearly to the head of the Gulf of California, with the Mexico side at least doubling the size of the habitat. Thus, the economy of region, like that of the Central Valley, lives and dies with agriculture. Other players include the DoD (Naval Air Facility El Centro), and recently, geothermal energy exploration, which has added a new dimension to the increasingly industrial landscape here. In many ways, the Imperial Valley resembles Mexico more than the U.S., with the workforce and population overwhelmingly Hispanic, and Spanish heard far more often than English in its towns and on radio stations.

Ornithological Summary

The habitats of the Imperial Valley, like other agricultural areas of the state, are heavily dependent upon water levels and water delivery infrastructure. First, it should be noted that the largest California populations of several species occur here. Between 30-40% of the global population of Mountain Plover winters within the Imperial Valley, almost exclusively in agricultural fields. Gila Woodpecker maintains its only California population away from the Colorado River in the Brawley area, and over 70% the state's Burrowing Owls are found here (http://www2.ucsc.edu/scpbrg/owls.htm). Late summer sees an influx of birds dispersing north from the Gulf of California which utilize the marshes and flooded fields of the Valley, including variable numbers of Yellow-footed and Laughing gulls and Gull-billed Tern, all of which are nearly restricted to this IBA and the adjacent Salton Sea in California (Yellow-footed Gull found nowhere else in the U.S.). Fulvous Whistling-Duck is an increasingly rare visitor to marshy fields and impoundments, and may be extirpated as a nester.

The impoundments within Finney-Ramer Lakes represent a critical year-round nocturnal roosting site for herons that forage during the day throughout the valley and at the Salton Sea, whose numbers build up during the summer and early fall with post-breeding dispersants. Fall roost surveys during 1999 (Shuford et al., In press C) recorded counts of 40,000 Cattle Egrets (August) and nearly 40,000 White-faced Ibis (October). About half California's winter population of White-faced Ibis occurs here (16,000 birds in mid-1990s, Shuford et al. 1996). These roosts are also critical for southern California's remaining wintering Sandhill Cranes, about 300 of which forage during the day in grain fields south of Brawley. Major nesting colonies of egrets are found at Ramer Lake (Great Egret) and in eucalyptus groves near Westmoreland (Cattle Egret). Agricultural fields, particularly when partially flooded, support thousands of wintering White-faced Ibis, Long-billed Curlew (c. 10% of global population, CBC data XX), both Snow and Ross' geese, along with tens of thousands of gulls (mainly Ring-billed). Shorebird use of these fields is exceptionally high during migration, both in spring and fall. Nearly 10,000 Whimbrel were recorded here on one count in April 1989 (Shuford et al., In press C), and fall migrants are joined by hundreds of Black Terns, particularly on fields close to the Salton Sea itself in the northern portion of the valley. Raptors have never been systematically censused here, but the wintering raptor community seems particularly dense, particularly during invasion years of northern buteos.

Unlined irrigation canals where grown to marsh vegetation support Least Bittern and scarce rails, including small numbers of California Black and Yuma Clapper rails (esp. Lower Finney Lake and Holtville Main Drain). These are often concentrated around wet spots where water seeps out of bases of the levees, a situation that also supports lush mesquite and riparian vegetation. These micro-wetlands surrounded by arid desert also support desert riparian species such as Lucy's Warbler and California's largest population of Vermilion Flycatchers (up to 20 pairs associated with the Highland Canal east of Holtville, RM). The riparian vegetation associated with unlined irrigation canals throughout the valley and with marshy impoundments appears to be very important for migrant songbirds, and a recent banding study by PRBO documented spring capture rates of Wilson's Warblers alone to be an order of magnitude higher than at Coyote Creek Riparian Station, a long-term banding station in the San Francisco Bay Area. This vegetation is also critical for the persistence of Colorado Desert species in the area, including Crissal Thrasher, Black-tailed Gnatcatcher, and Abert's Towhee.

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Conservation Issues

Shuford et al. (2000) summarize major conservation concerns for the Salton Sea and Imperial Valley. Those that pertain to this IBA include:

-Protecting and enhancing habitats for species of conservation concern, and those used by large numbers of roosting, nesting and foraging birds (incl. reducing disturbance by humans and predators).

-Continuing research on the impacts to birds of concentrations of heavy metals within the Imperial Valley/Salton Sea ecosystem.

-Evaluating the impacts of reduced water supplies and crop conversion (e.g. alfalfa to vineyards) agricultural fields in the IBA.

-Restoration of native riparian areas, including control of non-native species (e.g. tamarisk).

Ownership

Most of the wetland habitat is contained within units of the Sonny Bono Salton Sea National Wildlife Refuge and the Imperial State Wildlife Area (including Finney-Ramer Lakes), as well as a handful of private duck clubs. Other players include the DoD (Naval Air Facility El Centro), and recently, geothermal energy exploration, which has added a new dimension to the increasingly industrial landscape here.

Habitat

Most of the wetland habitat is contained within units of the Sonny Bono Salton Sea National Wildlife Refuge and the Imperial State Wildlife Area (including Finney-Ramer Lakes), as well as a handful of private duck clubs. The refuges also contain large fields of grains adjacent to marshes, similar to those hundreds of miles northwest in California?s Central Valley. Limited wetland and riparian (mainly tamarisk) vegetation is also associated with the two main rivers, the New and the Alamo, that flow north across the valley into to Sea. Both rivers are fed nearly exclusively by agricultural runoff, a situation that has been implicated in massive die-offs of birds at the Salton Sea. A mosaic of irregularly-flooded row crops, irrigation canals, and occasional remnants of native alkali sink scrub also contribute to the area?s staggering number and diversity of bird species nearly year round.

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