Washington State Snowy Plover Population Monitoring, Research, and Management: 2010 Nesting Season Research Progress Report

During the 2010 Western Snowy Plover (Charadrius alexandrinus nivosus) nesting season, we monitored breeding phenology, nest success, fledging success and number of nesting adult plovers in Washington. Field monitoring and research was conducted by Kathryn Gunther, Cyndie Sundstrom, William Ritchie, and Kerry Hosken with assistance from Marie Fernandez, Max Zahn, Warren Michaelis, Scott Harris, and Scott Pearson. Volunteers assisting with window, occupancy and adult surveys included: Ann Musché, Tom Finn, Carolyn Norred, Mary Ann Spahr, Bea and Jim Harrison, Normandie Hand, Tom Karczewski, Lori Summers, Kirsten Brennan, and Mark Hopey. A summary of some of our 2010 activities and results:

Breeding Phenology

• Clutches were initiated between 14 April and 18 July. However, very early nests could have gone undetected because intensive surveys did not start until after April 1.
• The first chick fledged around 22 July and the last chick known to fledge, fledged around 16 September.

Breeding Range

• Conducted 49 surveys on 14 sites to either assess occupancy or to count the number of nesting adults
• Snowy Plovers were only found nesting on Leadbetter Point and Midway Beach.

Number of Breeding Adults

• 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. Staff and volunteer surveyors conducted surveys, with volunteers contributing approximately >120 hours to survey efforts.
• The Washington population is declining by approximately 6 birds per year over the past five years (p < 0.001), and has declined from four nesting sites to two.

Nest success

• Thirty three nests were discovered and monitored.
• The percent of nests that survived from egg laying through hatching during the 2010 nesting season was 46% (including exclosed and non-exclosed nests).
• As in past years, the primary sources of nest failure were predation (primarily by crows and ravens), abandonment, and nests buried by drifting sand. We suspect that one nest was destroyed by humans based on human tracks and crushed eggs.

Fledging Success

• The 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.

Management Actions

• Restrictions: Beaches were closed to fireworks at locations where State Parks and U.S. Fish and Wildlife Service are the upland land owners.
• Nest exclosures: Fourteen nests were exclosed on the Wildlife Refuge at Leadbetter, and one nest was exclosed on State Park land at Midway Beach.
• Signing: Approximately 7.5 miles of beach was signed at Leadbetter and approximately 1 mile of Midway Beach was signed to restrict human access to the dry portion of the beach and protect nests. Access restrictions did not occur on private land.
• Nest Predation: Willapa National Wildlife Refuge began conducting preliminary surveys to collect data on nest predators occurring in and adjacent to the plover and lark nesting areas at Leadbetter Point. Logistics of implementing a proposed predator management strategy were investigated.
• Restoration: The U.S. Fish and Wildlife Service habitat restoration area (HRA) at Leadbetter Point is 121 acres, of which oyster shell has been added to approximately 62 of the 121 acres. Restoration and maintenance activities conducted in 2010 included: 1) Maintaining the 121 acre restoration area mechanically and through the use of herbicide; 2) The surface of the foredune and area between the foredune and the HRA that was treated with herbicide in 2009 was scraped using bulldozers to remove dead beachgrass. This has resulted in almost 3-miles of continuous, unvegetated access between the HRA and the outer beach, eliminating the need for alleyways cut through the dune to provide plovers with access between the beach and the restoration area. ; 3) In September 2010 an additional 67 acres in a mile long stretch of beach south of the existing HRA was treated with an aerial herbicide application, including the primary foredune and a portion of the outer beach west of the foredune; 4) oyster shell was added to approximately 8 acres of the restoration area to provide camouflage for ground nesting birds and to reduce blowing sand. The Leadbetter habitat restoration area supports the only known population of pink sand verbena (Abronia umbellata) in Washington State; a plant species that was thought to be extirpated in the state until its rediscovery in 2006. Seed dispersal and plantings have resulted in plants now occurring in all but the extreme northern portion of the HRA. In November 2009 pink sandverbena seed was collected in a collaborative partnership with the Shoalwater Bay Tribe. A tribal greenhouse facility was established and 20 plants were propagated and out-planted on tribal lands.
  
  Five experimental plot openings approximately 1 acre each were created on Leadbetter State Park to examine both plover and streaked horned lark response to treatments. Pre-treatment bird and plant monitoring was conducted by Washington Department of Fish and Wildlife with the assistance of Willapa Hills Audubon, Grays Harbor Audubon, and Shoalwater Bird Club volunteers (approximately 98 volunteer hours in 2010) and initial treatments to control non-native beach grasses were conducted by Washington Department of Fish and Wildlife. Pre-treatment vegetation data was collected in the summer of 2007, the first treatment occurred in October 2007 and the second treatment occurred in Sept.-October 2008. Expansion of plots to add approximately 2-3 additional acres, and a third herbicide treatment occurred in November 2009. Dead beachgrass was raked from the plots in February/March 2008 and 2009. One to three plover access cuts to the beach were bulldozed in each plot. Post treatment vegetation data was collected in August 2009. No plover or lark use was found during four surveys in summer 2009 or five surveys in 2010.

Recommendations

• Summarize, write-up and publish population monitoring results from Oregon, Washington, and northern California.
• Continue to examine the effectiveness of habitat restoration areas.
• Identify the conditions where plover populations are more likely to be self-sustaining.
• Conduct research to identify habitat features important to successful plover nesting.
• Initiate a study to examine the effectiveness of predator control.
• Continue to engage volunteers in monitoring.
• Continue to link management activities with research and monitoring.
• Continue to evaluate the effectiveness and continued use of nest exclosures on an annual basis.
• Evaluate impact and timing of clam digging on plover nesting, foraging and fledging.
• Initiate education and outreach activities.