Bird watchers in San Francisco are celebrating what they say is the first confirmed sighting of an osprey in the city.

A pair of the raptors was recently spotted nesting atop a container crane at Pier 80 in the city's Bayview-Hunters Point neighborhood, the San Francisco Chronicle reported. Bird experts say their presence is a sign that the waters around the pier are healthy. Ospreys subsist on fish.

"I'm totally stoked," said Golden Gate Audubon Society volunteer Eddie Bartley, who's been visiting the pier several times a week to watch the osprey. "Just the fact they're here gives you hope, like things are actually getting better."

San Francisco port officials said the birds haven't interfered with business. They have shut down the crane, which won't be used again until mid-summer.

Ospreys, black and white raptors that can have 6-foot wing spans, are common in Marin County and have been spotted in other parts of the San Francisco Bay area. The birds were nearly wiped out decades ago because of DDT, a pesticide that thins eggshells.

Bird experts said there previously were no confirmed osprey sightings in San Francisco, although there were unconfirmed sightings in 1996.

The ospreys at Pier 80 have given birth to a chick.

Clean-up efforts near the pier by port officials and the Golden Gate Audubon Society have been credited with luring the birds. Engineers dug channels and ponds, creating a marsh that filtered the bay and made the water clear enough for aquatic birds to see and catch the fish below.

"The fact they've chosen a place as dinged as the piers in Bayview-Hunters Point is a great, uplifting ecological story," said Allen Fish, director of the Golden Gate Raptor Observatory.