Golden Eagle Can’t Match Bulldozers : Regal Bird Declines as Southland Grows

Perched regally at the rim of her nest high on a sheer cliff, the golden eagle seemed unperturbed by the rumble of artillery fire from a distant practice range.

Over the years, the bird and her mate have become rather blase residents of Camp Pendleton. The nearby metal rigging that supports high-voltage wires sometimes serves as a spot where the birds take rest from their soaring flights.

The stream of trucks and cars traversing a ribbon of highway that leads from the Marine base’s Oceanside gate has become as familiar to them as the willow-dotted flood plain of the Santa Margarita River below their nest and the sunlit ocean beyond.

In fact, this pair of golden eagles, which routinely rears one or two chicks each spring, is faring much better than most in their majestic species who live in the Southland.

The golden eagle, its name derived from the adult’s burnished neck feathers, has been sharply declining in numbers in coastal Southern California as development creeps closer to their foraging areas and interrupts the peace and privacy they demand for reproduction.

Biologists say there is a chance that the species may go the way of their larger fish-eating cousin, the bald eagle, which vanished from Southern California by the 1950s and only recently was reintroduced on Catalina Island.

That is why a loosely organized group of naturalists, the Marine Corps and a local developer are engaged in a variety of efforts to help track and preserve habitats.

Pete Bloom, a research biologist with the Western Foundation of Vertebrate Zoology who was hired by the Marine Corps to identify nesting areas at Camp Pendleton, said there are records of 15 pairs of golden eagles that every year or two yielded offspring in Orange County, Camp Pendleton and the Cleveland National Forest. But Bloom said that was a couple of decades ago. Now, only seven of the pairs are producing eggs, and just half of those actually produce chicks.

In Orange County, Bloom said, development has pushed the remaining eagles to the border of the Cleveland National Forest, which offers seclusion but lacks the sage and grasslands they prefer for hunting a staple of rabbits and squirrels. Each eagle pair requires at least a 10-square-mile hunting and mating territory.

Bloom said that last year only one of the four eagle territories in Orange County that were active five years ago produced young. And so far this year his inspection of two nests found them to be empty of chicks.

While the golden eagle is not considered an endangered species from a national or state perspective--50,000 live in North America and 500 in California--many local biologists and conservationists such as Bloom are eager to keep the birds in Southern California.

“We are concerned because they are our eagles,” Bloom said.

One recent morning, Bloom rappelled down a 100-foot cliff to reach a 6-week-old chick, the latest offspring of the eagle couple that nest by the Santa Margarita River. After the mother flew away, he banded a foot of the big-eyed, black-and-white flecked youngster for identification.

He said the future of the golden eagle in coastal Southern California is threatened not only by a low reproductive success rate but also by a high mortality rate.

Of the chicks he bands locally, 13% are later discovered dead within 50 miles of their birth nests, Bloom said. By contrast, the national average for recoveries of dead eagles is 8% of those that are banded, he said. Frequently, he said, the birds are electrocuted by power lines or shot.

Bloom said he and other local naturalists warn developers and landowners, including the Marines, if their plans would place eagles in jeopardy.

For example, the sheer nesting cliff next to the Santa Margarita River that is believed to have been used by golden eagles for more than a century was saved twice in recent years, Bloom said. The Marines scuttled a plan to have new recruits practice rappelling there and then rejected a proposal to build base housing nearby.

Slader Buck, the supervisory wildlife biologist at Camp Pendleton, agreed with Bloom’s account, although a Marine spokesperson contended that the housing plan was never a serious option.

Camp Pendleton has become a refuge for much wildlife, including two other pairs of golden eagles, as areas around the base become increasingly urbanized, Bloom noted.

Nonetheless, he said, the base’s business of teaching warfare isn’t always compatible. For instance, he said, two nesting sites on the northern, coastal section of the base were abandoned by eagles 10 to 15 years ago because of troop maneuvers. At the time, he said, the military command didn’t know of the nests’ existence.

Buck said the camp hired Bloom to study the eagles in an attempt to monitor the birds. He said each spring his department evaluates the sites of major training exercises to determine if they will interrupt nesting areas.

On yet another front, Bloom frets about the potential threat to local habitats that could come with commuter highways planned between Riverside and Orange counties.

While factors such as the recent drought and pollution may be partly responsible for the declining local eagle population, Bloom insists that development poses the greatest menace.

In an attempt to preserve eagles in the face of development, the Irvine Co. has agreed to allow Bloom to reinforce and refurbish an old eagle nesting site just over a ridge from another nest in Gypsum Canyon, where the company plans to build a new community.

Eagles frequently use more than one nest in an area, and it is hoped that the pair that last nested in Gypsum Canyon will relocate before any houses are built, Bloom said.

Bloom acknowledges that the pair of eagles that live in Gypsum Canyon haven’t reproduced in at least three years, and even if they adopt a new nest, the birds would likely be losing hunting grounds to the new housing development.

“I give them about a 30% chance of surviving,” he said.

A Shrinking Habitat: Eagle breeding area. Source: The Audubon Society Field Guide to North American Birds

Golden Eagle Close-Up

Size: Female adults weigh about 12 pounds with wing span of 6 1/2 feet. Male adults weigh about eight pounds with wing span of six feet

Appearance: Brown feathers with yellowish hackles on back of head and neck.

Life span: Oldest eagle in captivity lived to be 45. They have been known to live up to 17 years in the wild. Fledglings in coastal Southern California have a high mortality rate.

Domain: Each pair requires a 10-square-mile foraging territory including grasslands or coastal sage scrub that supports its prey, mostly squirrels and rabbits.

Habits: Birds produce young every one to three years. The young travel up to 50 miles from their nests to establish their own territory. Mating pairs may reuse several nests in an area, which they refurbish and enlarge over the years. They are intolerant of human disturbance, particularly during nesting time.

Numbers: 50,000 birds in North America, including 500 in California.

Presence in Orange County: Four pairs of eagles in the county, all at border of Cleveland National Forest. Only one pair produced young last year.

Protection: Under federal law, the killing or capturing of the eagles or the collecting of their eggs or feathers is prohibited unless a permit is obtained for such purposes as scientific research or religious ceremonies. But destruction of their habitat is not expressly prohibited because the eagles are not considered endangered.

Sources: Los Angeles County Natural History Museum; Pete Bloom, research biologist for the Western Foundation of Vertebrate Zoology