The most celebrated birds in recent Philadelphia history are back for a second season of their popular avian reality show.

Their webcam is officially up and running. Last year, it gave thousands of viewers a peek-a-boo view of a red-tailed-hawk couple nesting on a ledge of the Franklin Institute. They hatched three young that flapped their way into the hearts of fans worldwide.

More than 300,000 people clicked in to one of two Web sites, some again and again. Some people - occasionally a dozen or more at a time - lined up on the sidewalk below to watch, waving at their friends through the webcam.

The birds were a hit not because they are rare - red-tailed hawks are common - but because the webcam offered such an intimate view. The camera was less than two feet away, inside a window.

Over the last month or so, the adults have brought new material to the nest, making it bigger and redefining the bowl in which the female can lay her eggs.

If the hawks follow roughly the same timetable, eggs could appear within two weeks. Last year, the female laid them March 9, and the chicks hatched April 16 and 17.

Institute president and chief executive officer Dennis Wint said there was no guarantee the birds would nest there again, of course, but "their behavior would indicate that they are likely to do so."

And that would make it another big year for Philadelphia's raptors.

The pair of bald eagles that nested the three previous years at the Navy Yard are gone - perhaps having moved across the river to New Jersey, if a new nest there is an indication.

They were the first eagles known to have nested within the city limits in more than 200 years and were hailed as dramatic evidence that the species, once headed for extinction, was well into recovery.

After these eagles came, two other pairs showed up, and they're still here.

At Pennypack Park in the Northeast, a pair that had two young last year have already laid eggs. Frank Windfelder, a nearby resident and president of the Delaware Valley Ornithological Club, said that on Feb. 9, one of the birds was sitting on the nest in a distinct posture that meant eggs were underneath.

"Somehow, they survived these snowstorms," Windfelder said.

At the John Heinz National Wildlife Refuge at Tinicum, an immature pair that built a nest but never laid eggs last year is back again, carrying sticks.

The staff is watching daily, hoping to catch sight of the dramatic eagle-mating display, said deputy refuge manager Larry Woodward. The two birds fly high, then clutch talons and plummet toward earth.

While the Navy Yard was inaccessible, both Pennypack and Tinicum offer spectators opportunities to see the birds without disturbing them, officials said.

Throughout Southeastern Pennsylvania and central New Jersey, the numbers of bald eagle nests have increased - so much so that officials wonder if territorial disputes will become the norm.

The drama for the Franklin Institute hawks reached a high June 6, when one of the young learning to fly left the nest for a practice run, but was unable to get back.

A wildlife rehabilitator from the Schuylkill Center for Environmental Education rescued the bird and put it back into the nest two days later, depositing it through an open window.

After the breeding season ended last year, the institute cleaned the feces off its windows and turned off the camera.

But the hawks' fans kept up their vigil all the same.

Della Micah of Plymouth Meeting continued her regular treks to the Parkway to keep an eye on the adults, which spent the winter in the area. She blogged about her sightings at http://sunnydixie.blogspot.com.

By now, there's also a Franklin Hawkaholics Facebook page, and as the institute's webcam sputtered into existence during testing this month, the posts mounted.

At one point, the hawks dropped off sprigs of pine and spruce, which John Blakeman, a retired biology teacher from Ohio and hawk researcher of four decades, said commonly happens.

"It's a sign of profound commitment," he noted on Micah's blog. "We're on for a good year of hawk-watching. Nothing like it in all the world."

Yesterday, as hawks added bits of paper and plastic bags to their nest, Micah said, she was glued to the webcam.

She knows that the next step in the birds' relationship - laying eggs and sitting on them - is not as exciting as when the eggs hatch and the parents bring bloody morsels of pigeon or rodent for them to eat, but she doesn't want to miss a detail.

"Having gotten to know these birds," she said, "they feel like old friends."