Biologists feverishly working to restore the Channel Islands National Park to a natural balance recently confirmed the capture of a breeding pair of golden eagles on Santa Cruz Island. They’re hopeful this was the last breeding pair of golden eagles on the largest of the Channel Islands.
Golden eagles have been prominent across the northern isles since the early 1990s and were originally lured over from the mainland by the abundant feral pig population on Santa Cruz. Golden eagles are lethal hunters and are known to take down small deer, which didn’t bode well for the endemic island fox populations that have historically been the apex predator on the chain.
However, with a 50-year absence of bald eagles, the golden eagles easily colonized the unique archipelago, and decimated fox populations on all the islands to the point that they’re now on the Endangered Species List.
Biologists became aware of golden eagle predation on island foxes in 1998, and soon after, captive breeding of foxes ensued on San Miguel, Santa Rosa and Santa Cruz Islands. The 5,000 feral pigs have nearly been eradicated from Santa Cruz, and biologists are buoyed by the potential recovery of bald eagles reclaiming their historic breeding grounds. Currently, 58 bald eagles have been released on Santa Cruz, and two chicks in separate nests hatched this past spring, the first known successful nests since 1949.
Since 1998, the Santa Cruz Island Predatory Bird Group captured and relocated the majority of golden eagles on the islands, but biologists from the Institute for Wildlife Studies chased and caught the last breeding pair of raptors with a net gun fired from a helicopter in rugged Laguna Canyon, located on the backside of Santa Cruz.
“This pair had developed a search image for foxes,” said Tim Coonan, terrestrial biologist and head of the island fox recovery on the islands. “We’ve been very effective removing eagles from the islands.”
The breeding pair of goldens had a chick in their nest. The parents were relocated to the Eastern Sierras, while the chick was placed in a hack tower in Southern California until it’s ready to fledge. After locating the nest, biologists found at least 12 fox carcasses in and around the nest. Some of those were without radio collars that biologists use to track the house cat-sized foxes across the 96-square-mile islet.
“This was the only breeding pair that we knew about,” continued Coonan. “We still expect to see more golden eagles searching for food in the fall and winter.”
Forty four golden eagles have been caught and relocated in various regions of Eastern California. Biologists are aware of three individual golden eagles inhabiting the island: two juveniles and one adult that haven’t been seen of late.
“Hopefully, the few remaining golden eagles out there haven’t keyed in on island foxes and what they look like,” he said.
Meanwhile, captive and wild fox populations are rebounding in the national park. This past spring, six pups were born in captivity on San Miguel, nine on Santa Rosa and 19 on Santa Cruz. Numbers in the wild still aren’t definite. On Santa Rosa, biologists know of at least three litters totaling 10 pups. Remote cameras are situated at known den sites on Santa Rosa and San Miguel. Sixteen captive foxes on each of the two northernmost islands will be released this coming fall.
“They [the foxes] do so well in the wild without predation,” explained Coonan. “Hopefully, the trend will continue upward and we won’t go backward.”