Out on a Limb : Development Encroaching on Bald Eagles’ Roosts at Big Bear

They return here each winter: distinguished bald eagles, stealthily swooping low over mountain lakes, standing sentry-like on patches of ice, perching proudly atop the tallest Jeffrey pines.

For years, this mountain valley has hosted the largest concentration of bald eagles in Southern California, wintering here from as far away as northern Montana.

By day, they patrol Big Bear and smaller lakes from the shoreline, scouting for dead fish or waiting to snatch a coot, their favorite waterfowl feast. At night, they retreat deeper into the quiet woods to roost in seclusion.

But there is growing concern that the endangered bald eagle is being squeezed out by development, and that these San Bernardino Mountains will no longer provide winter hospitality.

The U.S. Forest Service is in its third year of trapping bald eagles so they can be fitted with radio transmitters, tagged and monitored to determine how many return each year, and where they roost at night.

The objective, said Forest Service wildlife biologist Robin Butler, is to protect parts of the forest favored by the bald eagles. This is accomplished by learning where the birds spend their nights and ensuring that trails, campgrounds and other human amenities do not intrude on the birds.

The Forest Service started counting Big Bear’s bald eagle population in 1978. The numbers have ranged from as high as 28 in winter 1983-84, to as low as 12 in winter 1988-89. Last month, 16 eagles were counted in the valley by a score of volunteers who took positions around the lake and conducted a head count of the national symbol.

Local experts say the fluctuation in numbers is due, in part, to how harsh the winters are farther north and the availability of food. If local lakes are mostly frozen, the bird will migrate farther south.

But biologists and residents are fearful that the bald eagle could be scared away by residential and commercial development here, at neighboring Lake Arrowhead and at several adjoining lakes. The bald eagle can tolerate the intrusion of humans near its day perches, but demands seclusion at night.

Some residents are going to court to protect the bird. Ann and Dave Bellis, who live along Papoose Lake, just west of here, are suing San Bernardino County to force a new environmental impact report on a planned eight-acre subdivision near them. The land is a popular perch site for the bald eagle, they say.

Ann Bellis said the removal of 120 trees for street widening late last year was tantamount to an eviction notice for the eagles. She said she wants to halt construction on the housing tract--which was approved more than 10 years ago by the county--before more damage is done.

County officials said that because the tract was approved, it cannot be stopped.

Still, county planners say they are sensitive to development encroaching on eagle habitat. Four years ago, county land-use planners rejected a proposed resort because it was planned for an area that was host to both the bald eagle and rare plants.

Other proposed developments have been approved after plans were redrawn to save as many trees as possible, in accordance with the county’s tree protection ordinance, said Randy Scott, a county environmental planner.

The bald eagle is listed on national and state endangered species lists, although officials say it will soon be downgraded to a “threatened” species because its numbers have steadily increased in recent years. But state and federal wildlife officials cannot automatically block a proposed development because of the effect it might have on the bald eagle.

“Under the Endangered Species Act, unless there is a demonstrable, significant impairment to the eagle, we don’t have the authority to stop a project,” said Phil Detrich, coordinator of threatened and endangered species for the U.S. Fish and Wildlife Service in Sacramento.

So far, no one has been able to show that development at Big Bear has directly jeopardized the return of the bald eagle each winter. The northern shore of Big Bear Lake and the land surrounding Baldwin Lake is owned by the Forest Service, and is free of development.

Besides, experts note, it is politically harder to protect the eagles’ winter habitat because, unlike their nesting habits during the summer, they are transient in the winter. If the migrating eagles loses one winter site, they can search for another.

In Southern California, bald eagles have been spotted at Lake Perris, Lake Matthews and Vail Lake in Riverside County, Lake Cachuma northwest of Santa Barbara and as far south as San Diego County and northern Baja. Before post-World War II development, the wintering bald eagle was frequently spotted along the Southern California coastline as well, from Malibu to Laguna Beach.

The largest concentration of bald eagles in California is in the Lower Klamath and Tule Lake wildlife refuges in Northern California--home to about 500 wintering birds.

Wildlife experts are troubled by their inability to predict at what point bald eagles will abandon an area.

“Throughout California, there is a growing trend to develop around reservoirs,” Detrich said. “While we have not yet seen any use by eagles in those areas precluded because of that trend, I’d have to say we’re on the threshold of accumulative effects.

“The problem is, we can’t put our finger on that point when the threshold will be reached.”

Officials are not just worried about losing roosting sites to development. Even the loss of individual trees used by bald eagles for daytime perching can be cause for concern. The eagles typically rest atop dead, foliage-free trees that offer them unencumbered views of potential prey. But homeowners cut these trees down because they are considered unattractive or a hazard, forcing the bald eagle to look for another perch.

Butler said the Forest Service can at least try to protect its land for bald eagles, and embarked on the trapping program so it can learn where the raptors spend their nights.

So far, one roost site, used by as many as a dozen eagles, has been identified, near where the Forest Service planned to construct a trail. That trail will now avoid the area, she said.