Population and Habitat Objectives for Breeding Shorebirds in California's Central Valley

Khara Strum,W David Shuford,Monica Iglecia,Kristen Dybala

doi:10.15447/sfews.2017v15iss1art3

Abstract

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 (<10,000 individuals) or very small (<1,000 individuals) in three of the four planning regions, and avocet populations are small or very small in all four planning regions. We then used the framework to define long-term (100-year) population objectives for stilts, avocets, and a third species, Killdeer (Charadrius vociferous), designed to meet our long-term conservation goal of supporting self-sustaining, genetically robust, and resilient populations of breeding shorebirds in the Central Valley. We also estimated the long-term species’ density and wetland habitat objectives necessary to achieve the population objectives for all three species. The corresponding short-term (10-year) conservation objectives are to restore semi-permanent wetlands to provide an additional 11,537 ha (28,508 ac) of habitat for breeding shorebirds (by planning region: 2,842 ha in Sacramento, 2,897 ha in Yolo–Delta, 2,943 ha in San Joaquin, and 2,855 ha in Tulare), and to enhance existing habitat to support density objectives. Our approach provides a transparent, repeatable process for defining science-based conservation objectives for breeding shorebirds and their habitats in the Central Valley, which can help unite stakeholders around common goals and motivate conservation actions.

Highlights

The Central Valley’s climate and soils make it one of the most fertile agricultural regions in the world, and it provides over one-third of the vegetables produced in the United States (NASS 2016)
We evaluated three species of breeding shorebirds: Black-necked Stilt and American Avocet, which were considered in the 2006 Central Valley Joint Venture (CVJV) Implementation Plan (CVJV 2006), and Killdeer
Avocet, and killdeer as focal species because they are sufficiently common and widespread throughout the Central Valley to be used to evaluate the effects of management actions in focal habitats

Summary

Introduction

The Central Valley’s climate and soils make it one of the most fertile agricultural regions in the world, and it provides over one-third of the vegetables produced in the United States (NASS 2016). Renowned for the impressive numbers of waterfowl and shorebirds that use the region in winter and during migration, the Central Valley provides breeding habitat for seven species of shorebirds (Hickey et al 2003), including the American Avocet (Recurvirostra americana), Black-necked Stilt (Himantopus mexicanus) and Killdeer (Charadrius vociferous). The Central Valley currently supports nearly 24% and 17% of the national population of breeding American Avocets and Black-necked Stilts, respectively (Shuford et al 2007; USSCPP 2015). The most recent compilation of population trends and status for shorebirds in the United States listed the American Avocet as vulnerable to climate change, and the Killdeer as a common species in decline (USSCPP 2015). There is a need to protect and restore flooded habitat in the Central Valley during the shorebird breeding season

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Conclusion