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An extensive network of managed wetlands and flooded agriculture provides habitat for migrating and wintering shorebirds in California’s Central Valley. Yet with over 90% of historical wetlands in the region lost, Central Valley shorebird populations are likely diminished and limited by available habitat. To identify the timing and magnitude of any habitat limitations during the non-breeding season, we developed a bioenergetics model that examined whether currently available shorebird foraging habitat is sufficient to meet the daily energy requirements of the shorebird community, at either the baseline population size surveyed from 1992 to 1995 or double this size, which we defined as our long-term (100-year) population objectives. Using recent estimates of the extent of managed wetlands and flooded agriculture, satellite imagery of surface water, energy content of benthic invertebrates, and shorebird metabolic rates, we estimated that shorebird foraging habitat in the Central Valley is currently limited during the fall. If the population sizes were doubled, we estimated substantial energy shortfalls in the fall (late July–September) and spring (mid-March–April) totaling 4.02 billion kJ (95% CI: 2.23–5.83) and 7.79 billion kJ (2.00–14.14), respectively. We then estimated long-term habitat objectives as the minimum additional shorebird foraging habitat required to eliminate these energy shortfalls; the corresponding short-term (10-year) habitat objectives are to maintain an additional 2,160 ha (5,337 ac) of shallow (

The Central Valley of California provides important breeding habitat to numerous species of wetland-dependent birds, despite the loss of over 90% of naturally occurring wetlands. A majority of shorebirds breeding in this region rely on shallow-flooded habitat adjacent to sparsely vegetated uplands as provided by rice (Oryza sativa), managed wetlands, and other habitats. We estimated the current extent of potential breeding shorebird habitat provided by rice and managed permanent and semi-permanent wetlands in each of four major planning regions of the Central Valley, and estimated the average breeding densities and current population sizes of two species of shorebirds: the Black-Necked Stilt (Himantopus mexicanus) and American Avocet (Recurvirostra americana). Using a population status framework based on principles of conservation biology, we estimated that stilt populations are small (

Agricultural intensification has been a major factor in the loss of global biodiversity. Still, agricultural landscapes provide important habitat for many bird species, particularly in the Central Valley of California, USA, where >90% of the natural wildlife habitat has been lost. As wildlife professionals increasingly work with agricultural producers to promote ‘wildlife-friendly’ farming, it is important to understand the relative value of specific crops and field management practices to birds. The value to wintering waterbirds of seven treatments (crop and management practice combinations) across two crops (corn and winter wheat) was assessed at Staten Island in the Sacramento–San Joaquin River Delta of the Central Valley. Significant variation in the relative abundance of waterbirds was found among management practices, and post-harvest flooding and chopping and rolling (mulching) of corn were most beneficial to waterbirds. As expected, most waterbirds were common in flooded treatments, but geese, cranes and long-legged waders also were numerous in some dry treatments. Our data suggest that a greater waterbird species richness and abundance can be achieved by maintaining a mosaic of dry and flooded crop types, varying water depths and continuing the chop-and-roll practice for flooded corn. The observed benefits of particular crops and field management practices in this study should aid in the development of incentive-based programs to improve the habitat value of other working lands both within, and outside, the Delta. [ABSTRACT FROM AUTHOR]

Broad-scale surveys or monitoring of the distribution and abundance of waterbirds in the interior of the American West have been limited despite great losses of waterbirds' historic foraging and nesting habitats. Yet such work is crucial for assessing conservation status, population trends, habitat health, and the effects of management and environmental change on waterbirds. As part of the Western Colonial Waterbird Survey--an inventory of 19 species across 11 western states--we focused on three species of terns with conservation concern and assessed their distribution and numbers throughout their inland breeding ranges in California from 2009 to 2012. We compare these numbers to data from comparable surveys from 1997 to 1999. Climatic conditions strongly influenced the distribution and abundance of all three species, especially precipitation, which was below the long-term mean in relevant regions of the state for 3-4 years preceding the second round of surveys, greatly reducing foraging and nesting habitat. For the Black Tern (Chlidonias niger) and Forster's Tern (Sterna forsteri), respectively, statewide inland totals in 2009-2012 were about 49% and 26% of those in 1997-1999. Similarly, the numbers of breeding sites for those species were greatly reduced, particularly in northeastern California and the San Joaquin Valley. Patterns were less clear and varied regionally for the Caspian Tern (Hydroprogne caspia), as totals were greatly affected in all years by generally high, but variable, numbers at the Salton Sea. In northeastern California, however, drought reduced numbers of breeding Caspian Terns at least 10-fold from 1999 to 2009, and that region's contribution to the statewide inland total dropped from 68% in 1999 to 1% in 2009. It is unclear if these patterns for the three tern species will prove to be part of a longer-term declining trend or just a tribulation the terns faced from short-term fluctuations in precipitation. The latter may be likely given California's pattern of drought recurring about every 15 years through the 20th century. However, the relatively benign climatic patterns during this century may not persist in the future, and any drought effects come on top of the loss of >90% of California's historic wetlands and a severe over-allocation of the state's water resources. Designs for longterm monitoring of inland tern populations should consider the state's highly variable annual precipitation and the possibility of some species shifting among coastal and inland breeding sites. Management in the face of such variability and the uncertainty of future climate may be difficult, but securing adequate water in both dry and wet periods will be important as competition for supplies increases. [ABSTRACT FROM AUTHOR]