Kaua'i's white-tailed sea eagle, an Asian raptor that showed up on Kaua'i in December, may have moved on to O'ahu.

Fisherman Kea Chun, of Mililani, said he and friends were fishing at Iroquois Point Friday when they saw a pale-headed eagle attack a flock of white egrets and snatch one up in its claws.

"At first we thought it was a bald eagle, and then somebody remembered reading about the eagle on Kaua'i," Chun said. "We wondered if it was the same one."

U.S. Fish and Wildlife Service biologists said they had not yet heard of the eagle sighting, but would be watching for it.

The white-tailed sea eagle, a close relative of the bald eagle, has a pale head, but not as pale as that of a bald eagle. Both birds have brown bodies and wings, and white tails. White-tailed eagles are native to northern Europe and Asia. Wildlife officials believe the bird, which like the bald eagle eats fish as well as other birds and mammals, must have flown to Kaua'i from Asia.

The Kaua'i eagle appeared about December off the island's northern coast, where it fed on nesting Laysan albatross.

The flight from Asia to Hawai'i is a long one, but it is not unprecedented. A number of species of birds regularly migrate the more than 2,000 miles from the continents around the Pacific to Hawai'i. And every year, birds show up that are not regular migrants.

Smithsonian Institution fossil bird expert Storrs Olson has found eagle bones on O'ahu, Moloka'i and Maui, dating to before humans arrived in the Islands. Some were identified using DNA as white-tailed sea eagles. The early Hawaiian eagle must have also originated in Asia.

And there was a golden eagle flying in the Kaua'i mountains in the late 1970s and early 1980s. At the time, wildlife officials, doubting it could have flown across the ocean, suggested it might have been a released captive bird from a passing freighter. It was killed when it reportedly attacked a tour helicopter and was struck by the rotor.

The latest eagle has been spotted around the perimeter of Kaua'i as well as inland along cliffs in recent months, but had not been seen recently. Friday's sighting was the first reported from O'ahu.

Chun said he was fishing along the shore on Iroquois Point, and grass was being mowed on residential lawns nearby. A flock of egrets was clustered around the mowing activity.

The anglers saw an odd-looking large bird approaching over the land.

"It was cruising, just gliding, and occasionally flapping its wings," he said. "It had like a 7-foot wingspan."

Suddenly the egret flock flushed.

"It seemed like every egret on Iroquois Point took off. Out of nowhere, that bird grabbed one of them. There was a cloud of feathers. It flew away with the egret in its claws," he said.

The eagle flew off toward Pearl Harbor with the egret, and disappeared from view, Chun said. He described the bird as looking like photos he has seen of bald eagles, with a dark gray or brown body color and a paler head.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.