Western Snowy Plover

Gary Page and Lynne Stenzel (PRBO Conservation Science);
Caitlin Robinson-Nilsen (San Francisco Bay Bird Observatory)

Status: Uncertain – appears to be recovering in the South Bay.

The Western Snowy Plover is a federally threatened species under the Endangered Species Act. Primarily found nesting on coastal beaches, a subset of the population nests in San Francisco Bay. Plovers use dry pond bottoms, isolated islands, and levees in managed ponds as well as active salt ponds for nesting.

How long will it take Snowy Plovers to rebound to their 1970s level?

Snowy Plover chicks

Snowy Plover chicks

Snowy Plovers in San Francisco Bay have decreased from historic numbers but more recently show an increasing trend, possibly reflecting improved survey effort. Snowy Plover reproductive success is low in the Bay and has decreased over the past four years.

Threats

Predators impact Snowy Plovers by preying upon their eggs and chicks. Nest cameras have documented a large suite of predators, including California Gulls, Common Ravens, Northern Harriers and the native gray fox. Maintaining predator control measures is costly, and funds are scarce.

Habitat loss from salt pond conversion projects is a threat to the Snowy Plover, as some of the ponds it nests in are former salt ponds that are now being converted to marsh in the North and South Bay.

Rising sea level from global climate change may submerge the shallow ponds where Snowy Plovers nest.

Disturbance to nesting plovers by the public, from future public access and recreation trails.

Actions

Planning, Management, Restoration

Continue to control predators in San Francisco Bay, to reduce depredation of plover eggs and chicks.

Remove feral cat feeding stations near plover nesting areas in the South Bay, and educate the public about the need for this action.

Continue to create and improve plover nesting within restoration projects. Specifically, continue to create nesting islands, shallow ponds, and cover for plover nests and chicks.

Maintain 500 nesting plovers in San Francisco Bay, as set by the U.S. Fish and Wildlife Service Western Snowy Plover Recovery Plan. The South Bay Salt Pond Restoration Project aims to support 250 breeding Snowy Plovers. Other federal and state agencies need to collaborate to develop a strategy to support at least 250 additional plovers within San Francisco Bay.

Provide dry spring nesting habitat and late season nesting habitat. Initiate managed pond draw-down early enough in the spring to provide dry early season nesting habitat, and continue to draw down ponds throughout the season to create optimal late season nesting habitat.

Prevent avian predators from nesting and perching near nesting plovers by modifying the design of power towers and by removing predator perches (e.g. sign posts, old duck hunting blinds).

Prevent California Gulls from establishing colonies near plover nesting habitat.

Practice adaptive management. Support ongoing monitoring of managed ponds and nesting islands to determine their effectiveness in supporting plovers. Employ an adaptive management approach to pond design, acreage, and public access if the current plan proves to be ineffective.

Conduct public outreach to reduce disturbance to nesting plovers from public access and use of recreation trails. Close trails seasonally around nesting habitat.

Scientists

Experiment with substrates that provide cover. Test the effectiveness of oyster shells on the pond bottom to camouflage Snowy Plover nests and chicks, reduce predation, and increase nesting density.

Assess the implications of public access on nesting plovers to determine the level of disturbance likely from future public access and trail use. Determine consequence of disturbance on flushing rates, nest temperatures, incubation duration, and nest success of the plovers.


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