Vanishing Species : Environment: Eagles, falcons, hawks and other birds of prey are in danger as humans encroach on their habitat.

The graceful hawks that circle Ventura County skies will all but disappear early next century unless drastic steps are taken soon, wildlife experts say.

Hawks and other birds of prey--such as eagles, falcons, owls and vultures--were once plentiful in the county’s treetops, river bottoms, grassy flats and rolling hills.

Now, they share the same fate as other wildlife that competes with man for open space. Their numbers diminish each year as creeks are channeled between concrete embankments or fields and hillsides are landscaped with buildings and lawns.

For now, the red-tailed hawks that nest in the upper reaches of eucalyptus trees are still common sights in the county. But, like their fellow raptors, the red tails have dwindled from thousands in the last century to several hundred today, said James Wiley, research biologist with the U.S. Fish and Wildlife Service office in Ventura.

“These are sleek and beautiful and fairly intelligent birds,” Wiley said. “And their populations will all continue to decline.”

Swainson’s hawks still migrate through the county, but they can no longer find adequate nesting grounds here, biologists say. The golden eagle and the bald eagle are down to several pairs now living in the county.

The great California condor, the largest of the hawklike birds with an 8- to 10-foot wingspan, has fared worse still. There were once hundreds or thousands of them in Northern Ventura County and the Pacific Northwest. They are now extinct in the wild. Forty birds, 13 of them born in captivity, survive at the San Diego Zoo and the Los Angeles County Zoo.

“Those birds will not be here again,” said Wiley, who heads a project to bring the population back from extinction.

Neither the state nor the federal government has an active program to protect raptors, other than the giant condor, the Peregrine falcon and the bald eagle. Fish and Wildlife’s condor program evolved only after the bird was declared endangered. And at that point, it’s often too late to save the species, said Pete Bloom, a biologist with the Western Foundation of Vertebrate Zoology in Orange County, who has studied raptor populations in Southern California.

“It doesn’t protect the endangered species, let alone all the raptors that are not yet on an endangered species list,” Bloom said.

Ronald Jurek, a wildlife biologist with the state Department of Fish and Game, said the state had a large raptor conservation program during the 1970s to study and monitor populations.

“But since then, the numbers of endangered species have overwhelmed the people we have in the program to deal with them,” Jurek said. Of the 39 species of hawks, falcons, vultures and owls found in California, 22 are listed as endangered, threatened or species of concern, he said.

Of those, the condor, bald eagle, golden eagle, Swainson’s hawk, Ferruginous hawk, Peregrine falcon and burrowing owl live in or migrate through Ventura County.

The population declines can be blamed primarily on the disappearance of the birds’ habitat, Wiley and other scientists say.

Agricultural fields, though not as perfect a feeding ground as natural savannas, provide insects and rodents for birds of prey. But those fields are disappearing as the county continues to grow.

The birds also suffer from amateur hunters, poachers or children with guns, officials said.

Every year, the county Animal Regulation Department takes in 30 or 40 raptors that have been shot, said Jane Gorden, a county Animal Regulation clerk.

Other birds of prey are hit by cars or poisoned when they feed on rodents that have eaten pesticides, Gorden said.

“Sometimes they just come down to the ground from exhaustion or hunger,” Gorden said. “Some are just not able to find food.”

There is still some illegal trade in raptors for their feathers or for pets, officials said. But the birds inevitably fall ill from improper handling or feeding in captivity, said Ventura veterinarian Ron Dalzell, who donated his time to care for the county’s injured birds for 17 years.

“Every year, we had babies stolen from their nests, brought in by people who said they found them,” Dalzell said. Tree trimmers also dump birds from their nests every spring.

Two years ago, Dalzell stopped being a volunteer rehabilitator for the county and Jerry Thompson of Simi Valley took over some of his duties. Thompson has set up a network of three veterinary clinics to take care of the medical needs of the birds.

Many of the raptors, besides the pleasure they give to bird watchers, provide an important source of rodent control for agricultural interests and city dwellers, Bloom said.

“It’s a finely tuned ecosystem out there, and raptors are an essential part of it,” he said.

To ensure that the habitat survives for birds of prey and the land-dwelling creatures on which they feed, developers should be required to donate open space before they can build, the biologists said. Parks and open spaces should be linked by wildlife corridors of undisturbed land or riverbed. But Bloom doubts that will happen.

Robert Holmes, director of government affairs for the Building Industry Assn., said wildlife is already protected by the California Environmental Quality Act. That law requires an environmental impact report on any potential harm to wildlife by development.

“By law, we are required to look at the impacts any development will have on a species,” Holmes said. He added that developers already give away more land than they are required to.

He referred to the Ahmanson Ranch project in eastern Ventura County, where developers want to build 3,000 houses and 3 million square feet of office and commercial space. The developer, Ahmanson Land, has offered 3,000 acres of land to the National Park Service.

“This is far and away above the amount we are required to set aside by law,” Holmes said.

But opponents of the deal, including Save Open Space and County Supervisor-elect Maria VanderKolk, say Ahmanson had to offer the land to receive any consideration for a project that creates new development outside Ventura County city boundaries.

“We have got to set aside more open space for wildlife,” she said. “That has got to be the way of the future, because Ventura County is running out of land very quickly.”