This large IBA in the southern San Joaquin Valley consists of over 500,000 acres of protected lands and private agricultural areas located between I-5 to the west and 1-99 to the east. Hanford and Rte. 198 bound the north; the IBA extends 40 miles south to to Rte. 46 near Lost Hills. The major geological features are the ancient Tulare Lake Bed and the Sand Ridge south of the lake. Protected areas include Kern National Wildlife Refuge (NWR), Pixley NWR, Northern Semitropic Ridge, Allensworth Ecological Reserve, and Colonel Allensworth State Historic Park. Also included in this IBA is Creighton Ranch.
The ancient Tulare Lake Bed, once covering hundreds of thousands of acres, has now been reduced to a vast agricultural landscape of cotton fields and cement-lined irrigation channels. Periodically flooded fields and basins recreate the vast natural wetland habitats. The South Wilbur and Hacienda Flood Areas support nearly 20,000 acres of wetlands during wet years (TNC 1998). During dry years, the floodwater basins are colonized by native alkali scrub and grassland, along with their associated sensitive species.
Pixley NWR protects nearly 6,000 acres of native alkali grassland, alkali sink scrub, and riparian habitat. Its alkali grassland grows atop a unique interior dune system associated with the shore of ancient Lake Tulare. The surrounding landscape is dominated. Kern NWR protects just over 10,000 acres of alkali grassland, constructed freshwater marsh and scrubby riparian stringers. Several private duck clubs in the area contribute additional important wetland and native scrub/grassland habitat.
The Nature Conservancy's former Creighton Ranch Preserve lies along the historic path of the lower Tule River, just east of Corcoran. It features over 3,000 acres of Valley Oak and cottonwood-willow riparian woodland, freshwater marsh and alkali grassland with vernal pools. TNC gave up the property in the mid-1990s, and it is now managed by J.G. Boswell Co.
The Tulare Lake Bed is a true magnet for birds year-round. During the spring, winter and fall, any flooded field in this area can attract thousands of waterfowl, gulls and shorebirds, and in winter, these same fields become raptor habitat. Fall migration use of this IBA by shorebirds (August-September) can be higher than any other site in the Central Valley, as wetland habitat is scarce at this time elsewhere (Shuford et al. 1998). Burrowing Owl is still common in the area, particularly along the remaining unlined irrigation channels, and Short-eared Owls cruise fallow fields on winter nights. Dozens of Mountain Plover have been found in flocks in winter, particularly along Utica Rd. During the nesting season, any reservoir or pond left un-cleared can develop fairly extensive freshwater marsh habitat, which have hosted Least Bittern, rails, Black Tern, Tricolored Blackbird and other marsh birds. Though these species breed throughout the IBA, they often shift locations based on water levels and habitat conditions. Even the bare dirt levees around agricultural evaporation ponds and constructed (as mitigation) wetlands here and to the north toward Corcoran have become key habitats for birds, utilized by a suite of "alkali playa" breeders that includes Snowy Plover and several tern species. In fact, the Tulare Lake Bed remains essentially the only site in the San Joaquin Valley supporting numbers of breeding Caspian and Forster's terns, once common nesters throughout the original wetlands of the valley (Shuford et al. 1999), and this area has emerged as the major Central Valley stronghold for Snowy Plovers, a handful of which breed (Shuford et al. 1998).
Pixley NWR is known for its wintering flock of Sandhill Crane, which average about 3000 birds. The IBA also supports variable numbers of Mountain Plover that winter in a band west onto to the Tulare Lake Bed (Kings Co.) and south to the Kern NWR. Pixley is considered to be the most likely spot for breeding Long-eared Owl on the floor of the San Joaquin Valley (RH), and Short-eared Owl summers and probably breeds after wet winters. It is likely that with continued recovery of formerly-grazed grassland and riparian habitat, other species will rediscover this IBA, such as Yellow-breasted Chat and Grasshopper Sparrow.
This IBA may be most notable for the recovering valley grassland and alkali scrub bird community that has developed following the recent removal of grazing from large areas of the refuge. Short-eared Owl has re-colonized the area as a breeder (SF), one of the only places it nests on the San Joaquin Valley floor. The constructed marshes have proven attractive to large colonies (several hundred pairs) of breeding White-faced Ibis (fourth-largest colony in the state, Ivey et al. 2002) and Tricolored Blackbird, now localized breeders in the industrialized agricultural landscape of the modern-day San Joaquin Valley. Swainson?s Hawk has bred in the past 10 years (SF). Burrowing Owl, declining statewide, remains a common resident in the area. The canescens race of Sage Sparrow, resident in low numbers on the refuge, is common at Semitropic Ridge, as are Greater Roadrunner, a scrubland species otherwise very rare on the agricultural San Joaquin Valley floor (DS). Tens of thousands of wintering waterfowl utilize the refuge?s flooded fields and constructed wetlands, mainly Northern Shoveler (c. 25,000 in 2003), Ruddy Duck and Green-winged Teal; geese are much scarcer here than in refuges to the north (USFWS 2003b). Spring migration has brought thousands of shorebirds into the impoundments as they are being drained for the summer. In winter, small flocks of Sandhill Crane and Mountain Plover occur in drier agricultural fields in the area, both with much-reduced populations in the southern San Joaquin Valley. Though the original riparian bird community has not recovered, the refuge receives very little visitation from birders in the summer, and as the habitat continues to improve, it is likely that colonization by riparian obligates will occur. Interestingly, several native amphibians persist here in vernal pools on the valley floor, including Spadefoot Toad and possibly California Tiger Salamander (TNC 1998).
Some of the farthest-south nesting Swainson's Hawks in the state breed at Creighton Ranch, as do localized wetland species such as Northern Harrier and Tricolored Blackbird, given appropriate water conditions. Creighton Ranch and similar properties lie along the massive water conduit system of the Central Valley that ensures that water flows along irrigation canals. Mountain Plover and flocks of Sandhill Cranes formerly wintered at Cross Creek/Cottonwood Creek site up until the 1980s (fide B. Barnes), and still use fields and grassland in the area.
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Large areas of this IBA are managed for water storage and agricultural production, and by comparison a much lower percenage of protected areas. As with other large wetlands, communicable disease (e.g. avian botulism) has been a persistent problem, particularly during the breeding season. Agricultural runoff remains a major threat to breeding species. Unpredictable water management also poses an immediate threat, since nesting birds suffer if water is drained too quickly in spring. In upland areas, gazing pressure is intense, which limits its utility to grassland birds. Still, flooded agricultural fields have emerged as key summer breeding sites for many wetland bird species otherwise excluded from nesting on refuges due to lack of summer water.
Although the management plan at the Kern NWR specifies a goal of 7000 acres of wetland habitat, difficulties in obtaining water have resulted in about half that amount on average (TNC 1998), mostly present in winter only. A more pressing threat involves ever-increasing agriculture, which continue to alter the hydrology of the region by lowering the water table and pumping toxins into the air and water. Several thousand acres of evaporation ponds (for agricultural runoff) on the Tulare Lake Bed may pose a serious risk to birds in the area. Exotic plants (e.g. Tamarisk, Russian Thistle) pose a serious threat to recovery of riparian species throughout the IBA.
According to The Nature Conservancy (1998), over 90% of Creighton Ranch is potential seasonal freshwater marsh, yet water management practices often fluctuate water levels during summer, when nesting birds would require consistent levels for nest placement. For conservationists working in the area, saving these unique habitat patches in western Tulare Co. is literally a race against the clock. Valley floor habitat continues to be ploughed-under for agriculture, increasingly for vineyards on the eastern side of the valley.