Endangered Birds at Lagoon Will Get Help : Environment: A barrier will be removed to end flooding that prevented nesting of species such as the California least tern and Belding’s savannah sparrow.

A coastal barrier that has kept rare birds from reproducing at Batiquitos Lagoon in Carlsbad soon will be removed, the state Department of Fish and Game announced Tuesday.

The El Nino storms of the early 1980s created a large cobble blockage at the mouth of the lagoon that trapped water over areas where the California least tern and the Belding’s savannah sparrow traditionally nest.

The least tern is on federal and state endangered species lists, and the Belding sparrow is on the state list.

Fish and Game wildlife biologist Theresa Stewart said Tuesday that crews will close South Carlsbad State Beach part of next week while removing the cobble barrier that is 15 feet high, 30 feet long and 18 feet wide.

“There’s a dam out there, basically,” she said.

Carlsbad’s assistant planning director, Gary Wayne, added, “The lagoon just keeps filling.”

Over the years, the flooding of sensitive habitat has discouraged the rare species from nesting.

Stewart said 47 pairs of Belding’s savannah sparrows were reported at the lagoon in 1986, but that number has since dropped to fewer than 20 pairs.

“The population is declining, I don’t think we’ll get back up to 47,” Stewart said. “If we get 30, I’ll be happy.”

As for the least terns, last year only three pairs tried to nest, and Stewart figures, “if the water level is lower, we could expect 20 to 30 pairs.”

Although the numbers seem insignificant, Stewart pointed out there are only an estimated 1,200 pairs of least terns in California.

El Nino storms produced the barrier as the rough surf washed away the beach sand and left cobbles protruding 12 feet above sea level, enough to keep water from flowing out of the lagoon and opening the nesting areas.

It is critical to remove the cobbles now because the nesting season for the least tern begins in May, Stewart said.

She also believes that lowering the lagoon’s water level would benefit other species, including the snowy plover, the American avocet, black-necked stilt and Forster’s tern.

However, Wayne said the flooding problem won’t be solved permanently until the lagoon’s entire tidal system is opened.

He said that will happen under a $20-million lagoon restoration project to be finished next year. The project is now in the environmental review process.

The San Diego Audubon Society has endorsed the cobble removal plan.