Snowy Plover Numbers at 20-Year High

After 20 years of recovery efforts, the population of western snowy plovers in Oregon is increasing, but the small shorebird is still vulnerable.

The plover’s numbers had decreased for decades, mainly due to the loss of nesting habitat to non-native European beachgrass, but also because of predators, such as fox, crows, ravens and skunks. Direct human disturbance and human development also contributed to the bird’s decline.

Recovery efforts have included predator eradication and habitat restoration, as well as beach closures to keep humans, pets and vehicles away from nesting areas during breeding season.

According to data from a 2009 survey, approximately 208 individual plovers were counted along Oregon beaches between April and September, the highest number detected since monitoring began in 1990 when biologists estimated there were only 50 adult plovers in the same area.

“This year’s data is really encouraging,” said Dave Lauten, a wildlife biologist with Oregon State University’s Oregon Natural Heritage Information Center, which monitors plovers and their nests on the southern Oregon coast. “It appears that the work we’ve been doing with habitat and predator management is helping. A lot of the thanks has to go to beach visitors who help out by observing signs and leashing their dogs to give plovers space to successfully nest and rear their young.”

Human cooperation during the annual beach closures is appreciated because, as Megan Harper of the Bureau of Land Management said, “It’s an easy step that yields big results. People are doing a great job adhering to the beach closures and staying out of the plover nesting areas; it’s definitely helping with the recovery.” In the New River area, which is managed by the BLM, observers this year recorded the existence of 40 plover nests and 20 fledglings — birds that survive their first month of life and learn to fly. Thirty-one nests and six fledglings were counted in the state-managed Bandon State Natural Area, which runs south from China Creek off Beach Loop Drive.

Fledgling success

Lauten indicated that 193 chicks hatched this year from a total of 236 nests along the length of the Oregon coast.

“That’s the highest number of nests counted since the surveys began, but the real measure of success is how many nests produce fledglings,” Lauten said. “Overall nest success was relatively poor, with only 106 chicks, or about 50 percent of hatched chicks, surviving to independence.”

Despite the relatively low nest success rate, it was the fourth time in the past six years that Oregon has produced 100 fledglings or more. In years just prior to that, Oregon plovers had been producing only about 30 fledglings annually.

Lauten attributed most of the improvement in fledgling success to predator control efforts. “The biggest difference in our recovery program since 2002 is our implementation of lethal predator management,” he said.

Government trappers have removed numerous non-native red fox from both the New River and Bandon beach areas.

“This has had a good impact not just on plovers, but on the seabirds at Coquille Point, as well,” said Lauten. “We also started to control the ravens and crows.”

Ravens and crows usually do the most harm to the small birds by preying on eggs and hatchlings, but the biggest impact on plovers this year was caused by rodents.

“We don’t have a magic bullet right now for dealing with rodents,” Lauten acknowledged.

Managers may try trapping the predators in some areas, but they also hope rodent numbers will decrease naturally.

Managers also have worked to re-establish breeding habitat for the shorebird. Heavy equipment is used to remove invasive beachgrass in order to create open dry-sand areas for nesting and also to remove vegetation in which predators can hide. Once the grass is bulldozed away, workers must return in successive years to keep it from coming back.

“Once the sand is cleared and leveled, it makes great habitat for plover nesting,” said Harper. “Overall, we maintain about 150 acres of habitat for plovers at New River.”

Creatures of habit

The average life span of the western snowy plover is two to five years. The female plover can lay up to 12 eggs a year and may renest several times during a single season.

Plovers feed on insects found on the beach in the summer. During winter months, insect numbers go down, so plovers seek out blood worms near the water’s edge, like sandpipers do.

Lauten and other scientists have trapped and banded a number of the local plovers and kept track of them year-to-year. Probably 80 percent of Oregon’s plovers overwinter in this state, Lauten said.

Scientists hope for good overwinter survival rates for both adult and juvenile plovers. There are approximately 175 breeding plovers on the Oregon coast now.

“The goal of the recovery plan is to have a total of 250 breeding plovers between the states of Oregon (200) and Washington (50) combined,” Lauten said. “Oregon may be the first of the three states (the third is California) that actually meets recovery goals.”

Even if Oregon’s plover population returns to its historic levels, the scientists’ work — and the associated costs to taxpayers — will probably never end.

Lauten confirmed that if humans stop controlling plover predators and creating dry-sand nesting habitat, the bird’s numbers will again decrease to a point at which the species’ survival is threatened.

“This work is going to go on forever or until the Endangered Species Act laws change,” he said. “We’re stuck.”

Source:
http://www.bandonwesternworld.com/articles/2009/12/03/news/doc4b17002a0ea13360021514.txt

Snowy Plover Description:

The western snowy plover is a small shorebird distinguished from other plovers by its small size, pale brown upper parts, dark patches on either side of the upper breast, and dark gray to blackish legs. Snowy plovers weigh between 1.2 and 2 ounces. They are about 5.9 to 6.6 inches long.

The Pacific coast population of the western snowy plover breeds primarily on coastal beaches from southern Washington to southern Baja California, Mexico. The nesting season extends from early March through late September. The breeding season generally begins earlier in more southerly latitudes, and may be two to four weeks earlier in southern California than in Oregon and Washington.

Fledging (reaching flying age) of late-season broods may extend into the third week of September throughout the breeding range. Nests typically occur in flat, open areas with sandy or saline substrates. Vegetation and driftwood are usually sparse or absent. The typical clutch size is three eggs but it can range from two to six. Snowy plover chicks leave the nest within hours after hatching to search for food. They are not able to fly for approximately 4 weeks after hatching. Adult plovers do not feed their chicks, but lead them to suitable feeding areas. Adults use distraction displays to lure predators and people away from chicks. Adult plovers signal the chicks to crouch, with calls, as another way to protect them. They may also lead chicks, especially larger ones, away from predators. Most chick mortality occurs within 6 days after hatching.

Snowy plovers are primarily visual foragers, using the run-stop-peck method of feeding typical of Charadrius species. They forage on invertebrates in the wet sand and amongst surf-cast kelp within the intertidal zone, in dry, sandy areas above the high tide, on salt pans, on spoil sites, and along the edges of salt marshes, salt ponds, and lagoons. They sometimes probe for prey in the sand and pick insects from low-growing plants.