The Pacific coastal population of the Western Snowy Plover (Charadrius alexandrinus nivosus) is listed as Threatened under the Endangered Species Act, and is listed as Endangered by Washington State. The current Pacific coast breeding population extends from Midway Beach, Washington, to Bahia Magdalena, Baja California, Mexico. The Snowy Plover winters mainly in coastal areas from southern Washington to Central America. This coastal population nests primarily above the high tide line on a variety of beach and dune types including coastal beaches, sand spits, dune-backed beaches, sparsely-vegetated dunes, beaches at creek and river mouths, and bluff-backed beaches (U.S. Fish and Wildlife Service 2007). It also nests on sandy river bars, salt pans at lagoons and estuaries, salt pond levees, dry salt ponds, and on dredge spoils (U.S. Fish and Wildlife Service 2007). In winter, Snowy Plovers are found on many of the beaches used for nesting as well as on beaches where they do not nest (U.S. Fish and Wildlife Service 2007).
According to the U.S. Fish and Wildlife Service (2007), “Habitat degradation caused by human disturbance, urban development, introduced beachgrass (Ammophila spp.), and expanding predator populations have resulted in a decline in active nesting areas and in the size of the breeding and wintering populations”. In Washington, predators eating plover eggs, weather, shoreline modification, dune stabilization, and recreational activities have been attributed to reduced nest success and have been cited as the causes of local population declines (Washington Department of Fish and Wildlife 1995).
Historically, five areas supported nesting plovers in Washington (Washington Department of Fish and Wildlife 1995). Today, snowy plovers can only be found nesting on two nesting sites.
Both the federal and state recovery plans require monitoring of breeding adults and monitoring of fledging success to assess progress toward recovery goals. Monitoring is also necessary to evaluate the impact of conservation actions on plover populations such as the use of wire nest exclosures to exclude potential predators and the effectiveness of habitat restoration efforts. WDFW research is focused on addressing these research needs.
This work is funded by U.S. Fish and Wildlife Service and WDFW.
- The mean 2010 Washington breeding adult population was 43 (95% Confidence interval: 39-46). All of the breeding adults observed were found on Leadbetter Point and Midway/Grayland Beach.
- The Washington population is declining by approximately 6 birds per year over the past four years (p = 0.001), and the number of nesting sites has declined from four to two.
- The percent of nests that survived from egg laying through hatching during the 2010 nesting season was 46%.
- The primary sources of nest failure in 2010 were predation (primarily by crows and ravens) and nest abandonment. At least one nest was destroyed by humans.
- Average number of young fledged per adult male on the two nesting sites in Washington was 0.57 (95% Confidence interval = 0.53-0.62). Population viability analyses indicate that at least one young must fledge per adult male on average to have a stable population. As in past years, our results indicate that the Washington population should be declining which is consistent with trends in adult population estimates.
Scott Pearson along with Dave Lauten and Kathy Castelein from the Oregon Natural Heritage Information Center, and Mark Colwell from Humboldt State University are assessing various methods for detecting population trends using data from northern California, Oregon and Washington