3 Golden Eagles Fly Circles Around Capture Team
Heavy fog and some nifty flying helped the last three golden eagles on Santa Cruz Island foil an intense air and land campaign by wildlife managers to remove them from Channel Islands National Park.
The fox-eating eagles outfoxed pursuers in a helicopter by diving into fog banks, ducking under trees and zipping below jagged ridgelines. The two-week effort ended last week with the eagles still free and scientists pondering their next move.
“We don’t have a next plan right now,” said Brian Latta, a biologist from the UC Santa Cruz Predatory Bird Research Group who has spent three years capturing golden eagles on the island. “We are thinking about anything that might work.”
Removing the eagles, powerful predators not native to the islands, is vital to the park’s plan to release endangered island foxes this October. In the past, the eagles ate foxes to the brink of extinction until most of the foxes were put in kennels, awaiting the eagles’ departure.
There are now 91 foxes living in captivity on Santa Cruz, Santa Rosa and San Miguel islands, and the eagles have instead taken to eating feral piglets.
Since 1999, biologists have removed 22 golden eagles from 65,000-acre Santa Cruz Island, using folding bow nets baited with pig carcasses and hidden in the ground.
When the eagle steps on the net, the trap snaps shut. Captured birds are fitted with radio transmitters, driven some 800 miles to Goose Lake in far northeastern California and released. None have returned.
But nabbing the wily birds has proved challenging, with the remaining three wise to mistakes made by their captured comrades. They don’t fall for the bow nets anymore, and they elude helicopters by disappearing into fog or hiding in the trees.
“In 2000, we caught 11 eagles in four months; last year we caught five in a year,” Latta said. “Each successive generation gets harder to catch.”
The latest effort was done with near military precision. The island was blanketed by 18 to 20 spotters from almost every branch of the National Park Service.
Carrying binoculars and radios, they set off at 6 a.m. each day and, stationed on mountains and promontories, watched the skies until 6 p.m.
“You would tend to see them soaring along ridge tops,” said spotter Kate Faulkner, head of natural resource planning for the park. “You didn’t get a lot of time to see the bird as it moved through your area.”
Once a bird was seen, its position was called in to a command post where a helicopter pilot, a biologist and a net gunner were standing by. Within five minutes, they were in the sky chasing the eagle.
When the bird tired and landed, the helicopter hovered over it and a crew member would try to fire a net from what resembled a modified shotgun. The net entangles the bird, and Latta takes it from there.
“I’m the ‘mugger,’ the guy who gets the bird,” he said. “You put a hood on them, which calms them immediately, then wrap up the feet. They are so big you can cradle them in your arms.”
Golden eagles can stand 3 feet high with wings stretching 8 feet across.
Net guns were first used to capture golden eagles in the open grasslands of Wyoming, but this is their first application west of the Rockies, park officials said. The rugged island terrain, unpredictable weather and numerous trees have proved formidable obstacles.
In one case, a golden eagle landed five times but repeatedly eluded capture by scampering under a tree and hiding near a cliff where it couldn’t be safely netted.
Rhonda Brooks, who managed the recent project for the park service, said foggy weather reduced flying time to about four hours a day and high winds cut the effectiveness of net guns.
“In order to be successful we need to have a lot of things going our way,” she said. “We have given chase twice now with two different birds, but the areas weren’t safe or practical to fire a net gun. There isn’t much that has been written on this subject. In a way, we are writing the book on this.”
Removing the eagles is part of the $5-million island restoration that seeks to eliminate nonnative species of plants and animals--such as golden eagles, feral pigs and wild fennel--while restoring original inhabitants, including the island fox and bald eagle. Four bald eagles, which don’t eat island foxes, were released on Santa Cruz Island on June 25, and eight more will be freed in August.
Faulkner said the foxes have bred so much that if they are not released this fall, the park will have to build additional pens. She also worries that keeping the animals in kennels heightens the risk of disease or a fire that could wipe out an entire population.
“It’s important that we get them back into the wild as soon as possible,” she said.
Several new methods to capture eagles are being reviewed, including faster, more powerful helicopters that can maneuver in tight spots. The hunt may be delayed until fog clears out in the fall.
Biologists said tranquilizer darts wouldn’t work because of the bird’s thick feathers. Also, even if the drug penetrates the feathers it would take five or six minutes to work.
“The bird could fall out of the sky like a stone and die,” Latta said.
Killing the birds is, so far, out of the question.
“There is no talk of lethal means,” said Tom Dore, park spokesman. “These are California birds and we want to do everything we can to protect them. We have way too many options. Yes, it will cost more money, but it’s worth it.”
