Important Bird Areas

Yolo Bypass Area

California

Though a largely artificial system of spreading basins and controlled water releases, the Yolo Bypass is nonetheless one of the key freshwater marsh ecosystems in California. Other wildlife habitats include riparian forest and grassland, much of which is currently being restored. This IBA is centered within the historical wetland sink of Putah Creek and the outflow of Cache Creek, which flows east into the Sacramento Valley from the Coast Range. The Bypass itself extends south around the west side of Sacramento for about 30 miles, rejoining the river in the Sacramento Delta. It is intersected by both I-5 and I-80, main arteries north and west out of Sacramento. About 3600 acres south of I-80 was acquired by the Wildlife Conservation Board (DFG) and is being managed and restored for habitat as the Vic Fazio Yolo Basin Wildlife Area (formerly Yolo Bypass Wildlife Area). The rest of the Yolo Bypass includes the Trestle Ponds (City of Woodland), the Fremont Weir Wildlife Area, and several private landholdings, including much of the Conaway Ranch. The Cache Creek Settling Basin, Sacramento Bypass, Davis and Woodland Wastewater Treatment Plants, City of Davis Wetlands, and adjacent agricultural fields extends the IBA outside of the Bypass levees.

{link:For IBA map, click here.|http://www.audubon.org/bird/iba/maps/CA/CA239m_Yolo_Bypass_Area.pdf}

Updated October 2008

Ornithological Summary

The avifauna of the Yolo Bypass IBA is similar to that of the refuges north of Sacramento (see Sacramento Valley Wetlands IBA). Winter duck counts within the Yolo Bypass Wildlife Area have approached 40,000 individuals; Northern Pintail and Northern Shoveler are particularly well-represented. Concentrations of Snow and Greater White fronted Geese can exceed 100,000 birds. The Davis Wetlands hosts one of the largest concentrations of wintering Cinnamon Teal in the U.S (1000 birds, S. Hampton, via email)Up to 1000 Aleutian Canada Geese have been recorded staging in spring at the Yolo Bypass Wildlife Area. (S. England, in litt.) In summer, nesting waterfowl include large numbers of Mallard, Gadwall, and Cinnamon Teal. Rare, but regular nesters include Redhead and Blue-winged Teal. Over 300 Thayer's Gulls have been recorded in winter at the Davis Wastewater Treatment Plant, one of the largest inland concentrations of this species in the U.S. Remarkable numbers of shorebirds use seasonal and managed wetlands year round here, especially the ponds at Davis Wetlands and at the Yolo Bypass Wildlife Area. An impressive 37 species of shorebirds have been recorded in the IBA. Species that can number in the thousands include American Avocet, Greater Yellowlegs, Long-billed Dowitcher, Western and Least Sandpipers, Dunlin and Wilson's Phalarope. Unusual species such as Ruff are annual.(SH) The Trestle Ponds have hosted 10,000 shorebirds per day during spring migration when flooded. Species utilizing freshwater marsh habitat in summer include White-faced Ibis (thousands nest most years), Least Bittern (at Conaway Ranch, Willow Slough, and the Yolo Bypass Wildlife Area) and Yellow-headed Blackbird (many locations) Tricolored Blackbirds are irregular nesters, although in 1999 and again in 2006, 15,000 bred at Conway Ranch (SH). Northern Harriers nest in abundance in freshwater marshes, and even Short-eared Owl has been documented breeding in the Sacramento Bypass on the east side of the IBA (Ibid). Riparian habitat is rebounding within this IBA, and Yellow-breasted Chat is suspected of breeding in regenerating willow-cottonwood forest at the Cache Creek Settling Basin. Another riparian species, Swainson's Hawk, nests in the IBA as well (S. England, in litt.). Grassland restoration could lead to more surprises Grasshopper Sparrows have been recorded during the breeding season lately, though with no evidence of nesting (SH). Horned Larks nest in low numbers each year. Savannah Sparrows have nested in recent years. The "Modesto" Song Sparrow is a common nester (SH)

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Conservation Issues

The Central Valley Habitat Joint Venture Plan, developed by a consortium of private landowners, agency representatives and conservation scientists, called for the restoration of 20,000 acres of new wetland habitat within this IBA and over 10,000 acres were purchased in 2001(S. England, in litt.). Since large amounts of open space have already been acquired here, exotic plant invasions associated with constructed wetlands and agriculture are among the top conservation concerns. Though most of the southern portion of the IBA is probably secure from the effects of development, urban sprawl from the north (e.g. housing tracts associated with Davis) threaten to constrict the habitat locally. During the 1990s, a proposal to create a North Delta National Wildlife Refuge to adjoin Vic Fazio Yolo Basin Wildlife Area at its southern end was being examined by the USFWS, and may reemerge as a viable plan in the future. Local agencies have been trying to prevent water diversion from Conaway Ranch. Also, a local reclamation district recently de-watered the Willow Slough marsh and disced the entire marsh, approximately 200 meter wide by 1 mile long. This had been Least Bittern nesting habitat.

Ownership

About 3600 acres south of I-80 was acquired by the Wildlife Conservation Board (DFG) and is being managed and restored for habitat as the Vic Fazio Yolo Basin Wildlife Area (formerly ?Yolo Bypass Wildlife Area?). Cache Creek Settling Basin, within the Bypass, extends the habitat north of I-80. Nearby and adjacent to the bypass, several private holdings and restoration sites contribute greatly to bird habitat within the IBA, notably Conaway Ranch (incl. Willow Slough), Trestle Ponds (City of Woodland) and Davis Wetlands (City of Davis).

Habitat

Though a largely artificial system of spreading basins and controlled water releases, the Yolo Bypass is nonetheless one of the key freshwater marsh ecosystems in California. Other wildlife habitats include riparian forest and grassland, much of which is currently being restored. This IBA is centered within the historical wetland sink of Putah Creek, which flows east into the Sacramento Valley from the Coast Range.