Tern Around : Nature: Scientists are helping the endangered bird make a comeback by creating safe areas for nesting.
For thousands of years, the California least tern nested along the state’s beaches, laying sand-colored eggs and hatching sandy-gray chicks. That was a successful evolutionary adaptation in the days when the diminutive sea bird’s only significant predators were other birds and the occasional fox, coyote or rat.
But those sandy, camouflaged eggs have become a liability.
Unwitting surfers and sunbathers tromp on some. Beach maintenance crews roll over others. And at Camp Pendleton in San Diego County, the tanks and troops of the U.S. Marine Corps inadvertently pulverized a popular nesting ground.
Now biologists say the embattled California least tern, classified as an endangered species by the state and federal governments, is making a comeback.
The resurgence of the bird is due largely to efforts to create safe nesting areas, experts say, such as one biologists are building in Playa del Rey.
Final plans for the sanctuary, including its exact configuration, were being negotiated late last week between the Los Angeles County Department of Beaches and Harbors and the two biologists who organized the project, Pat Baird of Cal State Long Beach and Bryan Obst of UCLA.
But the basics are clear: A four-foot-high chain-link fence will be erected on Dockweiler State Beach, about half a mile south of the main channel to Marina del Rey. The fence will enclose roughly an acre of sand on the ocean side of the popular coastal bicycle path. Inside the sanctuary, the biologists will place about 70 least tern decoys and a continuous tape recording of the tern’s shrill call.
Baird and Obst hope that the decoys and calls will attract terns and create the second nesting area for the birds along Santa Monica Bay.
“This site is really important because you want to spread out an endangered species as much as possible to avoid unusual events that could do it harm,” Baird said last week, as she surveyed the site of the Playa del Rey sanctuary.
The area’s first least tern sanctuary, just a mile to the north on the Marina Peninsula, has become one of the most successful breeding grounds for the birds.
The biologists decided to form a second preserve because the four fenced acres on the Marina Peninsula have become overcrowded with terns. About 200 nesting pairs used the Marina site last year.
They also hope to avoid “unusual events” that could decimate a lone colony. Last year, for instance, a single cat got loose in the Marina Peninsula sanctuary and fed on so many tern chicks that it could have wiped out the entire nesting cycle, Obst said.
The cat was eventually trapped and the colony preserved, but the incident reinforced the need to find a second nesting site for the birds in Santa Monica Bay.
The biologists’ program is funded by a $60,000 grant from the Environmental Protection Agency and sponsored by the Santa Monica Bay Restoration Project, a coalition of government and business officials that is attempting to clean up the bay.
The terns nest on the California coast after wintering in southern Mexico and Central America. Only about nine inches long, the tern has a white forehead, black crown, yellow beak and rapid wing beat.
The bird lays its eggs in April and May in shallow impressions in the sand.
Previous efforts to protect nesting areas have proven successful, even at Camp Pendleton. The birds lost much of their turf along the beach, but a fence was installed in 1987 and the sanctuary has become home to one of the most prolific colonies along the coast, Baird said.
The birds hit their low point in the mid-1970s, when just 600 nesting pairs were spotted from San Francisco Bay to the Tijuana River. But by the late 1980s, that number had more than doubled. Last year, 1,708 pairs were counted.
In addition to the Venice and Playa del Rey preserves and a third sanctuary at Los Angeles Harbor, biologists hope that the bird will be encouraged by the restoration of the Ballona Wetlands adjacent to Playa del Rey.
The owner of the property, McGuire Thomas Partners, has agreed to set aside 260 acres of the wetlands as one condition of developing adjoining acreage with homes and offices.
The biologists said they hope that least tern colonies will help educate the public, as well as save the birds.
Obst noted that wildlife preservation is usually out of sight and out of mind for most people.
“We are using this project to let people know about the plight of endangered species,” Obst said. “It is demonstrating that you can have compatible uses between the public and endangered species.”
On beach nesting
grounds, the California least tern’s camouflaged eggs and chicks once offered protection from predators. Today, that evolutionary adaptation has become a liability.
THE LEAST TERN
The least tern (Sterna antillarum) competes with people every summer on sandy beaches in its determined effort to nest. Among the bird’s distinctive features are a slender body, rapid wing beats and shrill cry. The birds are very noisy when feeding. They seek small fish close to shoreline or in protected bays and ponds, hovering high above the surface or skimming low over the water.
In 1975, there were 600 nesting pairs of least terns along the Pacific Coast. In 1990, there were 1,708, thanks in part to efforts like the one at Playa del Rey.
Typically, the bird lays 1 to 4 eggs. The incubation period is 20 to 25 days.
In breeding plumage, the least tern has a broad white forehead framed by a black crown and a black line running from the crown through the eye to the base of the bill. The mantle and the short forked tail are pearl-gray.
Source: Audubon Society Master Guide to Birding
