Until the mid-1800s, the southern San Joaquin Valley boasted the largest freshwater wetland complex in the western U.S., extending a half-million acres across what was to be known as the Tulare Lake Basin. Three main basins were involved, with the massive Tulare Lake Bed in the north and the Buena Vista and Kern Lake Beds southwest of present-day Bakersfield. Agriculture, both row crops and grazing, expanded through the early 1900s, and by the mid-1900s, Isabella Dam largely halted the regular winter floods in the area. During the 1960s and 70s, the region was converted to a highly mechanized landscape of manicured corporate farms with heavy pesticide use and highly limited bird habitat. Today, cracks in the levees, both literally and figuratively, have allowed water to escape containment, fields to go fallow, and habitat to flourish again, mostly out of sight to the thousands of motorists along I-5, which cuts through the middle of the Buena Vista Lake Bed. Key areas for birds here include large (1000s of acres) water banks both east and west of I-5 within the historic Kern River bed that are flooded by the county when water reserves are above normal; Cole's Levee Ecosystem Preserve, a 6000-acre, privately-owned gem of riparian, grassland and alkali sink scrub just north of the Buena Vista Aquatic Recreation Area west of I-5; and several smaller overflow basins just north of South Lake Rd. east of the town of Taft. Other patches of un-plowed valley floor (e.g. Tule Elk Preserve, southeast of Buttonwillow) have received little attention from field ornithologists but have high potential for grassland and riparian birds.
Though historical records from this IBA include such phenomena as nesting colonies of American White Pelican (e.g. Linton 1908), a surprisingly large subset of the former avifauna persists, albeit in reduced numbers. So, while the region's bird communities have not returned to pre-1950s conditions, they are certainly occupying every shred of available habitat. The Kern Water Bank east of I-5 has recently hosted up to 100 White-faced Ibis summering, along with breeding Northern Harrier, White-tailed Kite (c. 15 pairs summer when flooded), and is one of the few San Joaquin Valley-floor areas where scarce riparian birds such as Yellow Warbler and Yellow-breasted Chat persist in summer. The water bank west of I-5 was found to support Forster's and Black Terns during surveys in 1998 (Shuford 1998a). Cole's Levee has been little-studied by birders, but is expected to support a similar subset of birds. Tricolored Blackbirds have a traditional breeding area at the Tule Elk Preserve (TNC 1998). The overflow ponds east of Taft are notable for large numbers of shorebirds and waterfowl in migration and winter (when at least partially flooded), and for high numbers of Burrowing Owl, which seem associated with the dirt banks of the California Aqueduct through this area. Prairie Falcons summer in this area, and often forage around these ponds, where they are joined by numerous other raptors during migration and winter, many of which roost in trees along the Kern River (SF).
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Due to the high degree of degradation to this IBA, and the fact that any habitat is either in private hands or is managed by county agencies with no clear habitat conservation mandate, a "Critical" threat designation is warranted for the entire IBA. Though Conservation issues affecting the area range from unreliable water levels to toxins in the soil and water, the fact that so little habitat remains means that any amount of conservation activity through easements and management agreements can have marked effects on bird populations in this portion of the San Joaquin Valley. Though an overwhelming majority of the region is in private hands, the Buena Vista Aquatic Recreation Area, basically in the center of the IBA, is a county-run fishing and boating park (incl. Lake Webb/Lake Evans) with tremendous (unrealized) conservation potential, both along its borders and in the area outside the levees of the lake. Patches of riparian thickets here could be expanded and protected, and freshwater marsh vegetation encouraged where appropriate. Recent expansion of urban sprawl west from Bakersfield continues to degrade habitat within this IBA through encroachment and direct habitat loss, particularly along the Kern River.
Habitat within this IBA is either in private hands or is managed by county agencies.
Key areas for birds here include large (1000s of acres) water banks both east and west of I-5 within the historic Kern River bed that are flooded by the county when water reserves are above normal; Cole?s Levee Ecosystem Preserve, a 6000-acre, privately-owned gem of riparian, grassland and alkali sink scrub just north of the Buena Vista Aquatic Recreation Area west of I-5; and several smaller overflow basins just north of South Lake Rd. east of the town of Taft.