Dave Garcelon dangles precariously over the huge bald-eagle nest on the southeastern cliffs of Catalina Island.
He hangs from a harness connected by a long rope to a helicopter hovering 120 feet overhead.
It’s the second time Garcelon has visited the nest in a month. In early April, he removed an egg and replaced it with a synthetic one. As he approaches the nest this time, Garcelon again disturbs the nesting bird, and it takes off, soaring through the sky.
In less than a minute, Garcelon has replaced the fake egg. The eagle and its mate return to find a two-week-old eagle chick.
“The adults immediately came back and started to brood it, and then later we saw them feeding it,” said Garcelon, 40, president of the Institute for Wildlife Studies in Arcata in Northern California.
The eagle chick was hatched in a San Francisco Zoo incubator from an egg laid by captive birds. It was the 42nd bald eagle released on Catalina Island under a reintroduction program Garcelon started in 1980.
When the chick is old enough to fly in 11 or 12 weeks, it has roughly a 50-50 chance of survival, Garcelon said. But that’s better odds than if the eagles had tried to hatch their own egg on the island.
Human intervention is still the only way to ensure the survival of the endangered species, said Garcelon, who has worked for 14 years to re-establish bald eagles on Catalina.
At least six breeding pairs of bald eagles were nesting on the island in the 1940s. They were among the 25 to 40 pairs on the eight Channel Islands before the population was wiped out by hunting and pesticide poisoning.
DDT left over from extensive use in Southern California agriculture continues to permeate the environment and show up in the fatty tissue of birds and other wildlife. The pesticide was outlawed in 1972.
DDT affects the calcium deposits in the eggs of eagles and other shorebirds, Garcelon said. The eagles lay eggs with shells so thin they easily break or lose water, causing the embryo to dehydrate.
“We’re able to save at least some of them until hopefully the environment cleans up well enough that they can do that themselves,” he said. “One of these days that stuff (DDT) will degrade and be out of the environment.”
Now Catalina is home to two breeding pairs and an additional nine mature birds, all reintroduced. Garcelon said an unequal sex ratio prevents more breeding on the island.
When eggs are laid, Garcelon quickly replaces them with replicas.
The fragile eggs are transported in a specially designed padded case to San Francisco for incubation. Sometimes a chick goes back to the parents that laid its egg, but only three of 14 eggs laid on Catalina since 1987 have been successfully incubated.
The egg removed from its Catalina nest in early April, for example, did not hatch.
After the chick is left in the nest, the adult birds quickly take on the role of parents. Only one foster chick has died in a Catalina nest, Garcelon said.
As the birds mature, they often leave the island for three or four months. Wing tags and radio transmitters help Garcelon monitor their travels.
One bird released in 1991 was spotted on the California/Oregon border earlier this year, he said. But eventually it may return.
“We expect them to come back to at least the general area of Catalina Island because they have what’s known as a ‘natal site tenacity’ and like to breed in the same area they came from.”
Garcelon’s aim in forming the nonprofit wildlife institute in 1979 was to re-establish bald-eagle populations, but he said he was not aware of how prevalent DDT was in Southern California waters when he began the Catalina project.
Garcelon hoped the birds would be producing their own healthy chicks by now. Only one pair has laid and hatched an egg unaffected by DDT.
Garcelon’s organization and the Catalina Conservancy have spent more than $700,000 in private funds trying to bring the species back.
In the past three years, the U.S. Fish and Wildlife Service has contributed an additional $255,000 to the program.
It takes $150,000 a year to maintain the program, but it’s money well spent, Garcelon said.
Garcelon added that the only other bald-eagle program in California is on the Big Sur coast.
He has reintroduced the eagles in several other locations, including Lake Tahoe, British Columbia, Arizona and New Mexico.