Floating Nests Proving a Good Neighborhood for Clapper Rails

Five months after construction, Dick Zembal is ready to call his little housing project in the soggy salt marshes of Anaheim Bay a success.

Although an occupancy rate of 64% won’t break any real estate records, Zembal called the response to his development scheme “incredible--better than my wildest dreams.”

Tenants of these spare but cozy floating homes are light-footed clapper rails, elusive and endangered marsh birds whose numbers at Anaheim Bay, part of a national wildlife refuge within the Seal Beach Naval Weapons Station, have taken a sharp dive in recent years. From 24 pairs counted before the 1984 breeding cycle, the numbers have plunged to 11, 5 and 7 in subsequent seasons.

The decline in Anaheim Bay mirrors a statewide trend: 277 pairs were counted in 1984, but only 178 pairs were counted before the just-concluded 1987 breeding season, 119 of these concentrated at Upper Newport Bay.

Zembal said the birds are “about the size of a skinny chicken,” brown and rust in color with white streaks on their flanks and under their tails. They feed and hide in dense marsh vegetation the year round.

Zembal, a U.S. Fish and Wildlife Service biologist and chairman of the agency’s recovery team for coastal endangered species, is hoping to reverse the decline in the bird’s population. Anaheim Bay has been the focus of his recovery efforts.

In his newest plan, he waded in mud up to his hips to place 28 wooden platforms, each with a tumbleweed tied neatly to the top for cover, in the refuge’s lower salt marsh. Two long wooden dowels anchor the platforms so that during high tides the platforms rise neatly, like an elevator, without floating away. The platforms were placed in March.

While monitoring the nesting sites during the recent breeding season, from April through July, Zembal found 18 nests, 12 with egg clutches (a typical clutch has four to nine eggs). Evidence at the sites suggests that there was at least one successful hatch from each clutch, but biologists will have a better idea of the survival rate after next spring’s bird count.

The results have been surprising, Zembal said, since just seven pairs of clapper rails had been counted in the 1987 spring census.

Zembal won’t take full credit for the ingenious and successful design of his nesting platforms. “It’s not really an original idea,” he said during a recent tour of the marsh. “It’s the exact same thing the clappers do.”

Light-footed clapper rails prefer to build floating nests of dead cordgrass, a long-bladed plant common to salt marshes. Under ideal conditions, their nests are built directly on the mud of the marsh and intertwined with living stems of cordgrass, so they will be anchored when high tides flood the marsh.

The problem at Anaheim Bay, Zembal found, is that the cordgrass is simply too short; the nests would be covered with water during a high tide. The problem is compounded because the Seal Beach marsh is slowly sinking with the extraction of water for agriculture and oil drilling.

The birds at Anaheim Bay have reacted by building their nests on raised berms in the marsh. But most of these are old roadbeds connected to the dry land, making eggs and hatchlings easy marks for marauding predators.

Skunks and possums prey on the clapper rails, but in recent years, the most notorious culprits have been red foxes, which are not indigenous to the area. Populations of the endangered clapper rails and California least tern have dropped precipitously since the foxes were first spotted in the refuge in 1982; now, during his census counts, Zembal said, foxes routinely outnumber clapper rails.

(Officials at Seal Beach Naval Weapons Station began a program to trap the foxes in July, 1986, in a bid to protect the clapper rail and the California least tern. Last September, a judge denied a request from the Orange County-based Animal Lovers Volunteer Assn. for an injunction to stop the trapping; an appeal date is pending. Navy officials refused to comment on the legal action and also declined to say whether trapping has continued.)

Even before foxes became a problem, Zembal hoped to lessen the threat from predators by building isolated hummocks in the marsh. In 1982, he collected permits from various agencies to build 25 of the potential nesting sites. But he gave up after just five because he was unable to build them high enough.

“It was extremely hard work. We had to carry the soil by hand,” Zembal said. A contractor was hired to build the mounds mechanically, but his equipment bogged down in the muck.

Such permanent nesting mounds, built with the help of helicopters or barges, are still Zembal’s long-range goal. But such a project would be expensive, so in the meantime he is concentrating on his floating wooden platforms.

He plans to have 50 of them in place by the opening of the next breeding season.

Although encouraged by the early success of the structures, Zembal and other state and federal wildlife officials are waiting for next year’s spring census to see how many of this year’s young clapper rails survive.

“Based on the numbers . . . I would say it’s a success,” state Fish and Game wildlife biologist Ron Hein said of Zembal’s program.

“I think what Dick is experimenting with may be part of the puzzle to improve the population there,” added Hein, who supervises state wildlife reserves in Orange, Imperial and San Diego counties.

“Anything that simple that works for an endangered species is good news,” said Victor Leipzig, a biology instructor at Irvine Valley College who also serves as president of Amigos de Bolsa Chica and as a director with the Sea and Sage Chapter of the National Audubon Society.

“It’s important not only to maintain the precarious population at Seal Beach but also to expand it.”

So far, Zembal said he has seen only one sign of predation at the sites: One egg had been pecked by a small bird, perhaps a robin. But in that case the parents had built their nest outside the cover of the tumbleweed.

So far the platforms have not been bothered by the foxes, but Zembal is afraid the predators eventually will associate the platforms with an easy meal. His plan is to have more platforms than nesting pairs of clapper rails.

“I want enough so that a red fox can visit 10 and never find a nest,” he said.

He’s not sure why the number of successful nests at Anaheim Bay outstrips the number of breeding pairs of birds counted in the spring census. He places faith in the count, and believes some of the nests at Anaheim Bay may have been built by birds that have moved north from Upper Newport Bay.

“Light-footed clapper rails are thought to be very sedentary. That’s probably generally true,” Zembal said. But the habitat at Upper Newport Bay is saturated, so some of the young birds may be moving to Anaheim Bay in search of less crowded spaces.

Zembal said he thinks that many youngsters raised at Upper Newport Bay are being crowded out of the marsh, and many are being eaten by predators. “A few of them are bound to try something outlandish,” he said.

There is one piece of evidence to support Zembal’s theory that birds can make the 15-mile trek north: Recently, a bird banded at Upper Newport Bay was found in Anaheim Bay.

Zembal has studied the light-footed clapper rail for eight years, not only in his capacity with the U.S. Fish and Wildlife Service but also under contracts with the state Department of Fish and Game and on his own time. He has written technical articles about the bird.

Biologists and ornithologists are worried because more than half the light-footed clapper rails in California (they are found in no other state; some live in Mexico) are concentrated in Upper Newport Bay.

“It scares me that there’s only one significant population of clapper rail,” Zembal said. An unforeseen mishap there could mean disaster, which is why he is working so hard to re-establish the bird at Anaheim Bay.

“It’s a safeguard--you don’t want to put all your eggs in one basket,” Hein said.

Leipzig pointed out that as clapper rail numbers shrink, so too does the genetic diversity of the remaining population, leaving the birds even more vulnerable to changes in their environment. If the Seal Beach or other precarious populations were lost because of a severe storm or pollution, he said, “we’d have to fall back on the Newport Bay population (to repopulate the site), and if you do that often enough, you’re pulling all your individuals from one source, and that’s genetic trouble.”

Zembal said that Anaheim Bay, with twice the acreage of salt marsh of Upper Newport Bay, could support a viable and substantial population of light-footed clapper rails. “If my theory holds true,” he said, “the only thing missing here for the clapper rails is nesting sites.”

And with the initial success of the floating marsh houses, that problem may soon be solved.