There's a new bird in town.

A young male peregrine falcon now reigns over the Cathedral of Learning nest in Oakland, and he's shown a penchant for beating up on red-tail hawks.

But the real flap is figuring out what happened to Erie -- the peregrine patriarch who'd ruled the roost since 2002 and fathered 22 chicks with the current matriarch Dorothy.

Now that Erie has flown the coop, Dorothy has taken up with a handsome younger male, temporarily named Erie2 -- E2 for short -- and is looking after four eggs in the 40th-floor perch.

It's the latest episode in the falcon soap opera that Kate St. John, a WQED employee and volunteer for the National Aviary, is documenting. She's monitored the University of Pittsburgh peregrines for many years and was first to notice and confirm that 9-year-old Dorothy has a new love interest.

"I thought it was going to be another ho-hum season, and now it ain't," Ms. St. John said. "I grieved a little [for Erie]. They're not pets, but it's something that I spent time with for so many years, and they are individuals. So it's hard. The one I cared about is gone."

The peregrine population in the United States dipped to 324 pairs in 1975 due to the pesticide DDT. They're still endangered in Pennsylvania, which had only 12 pairs in 2006, but the population is growing with the help of nesting boxes atop the Gulf Tower and Cathedral of Learning.

Peregrines are the world's fastest creatures, able to dive 200 mph to catch birds on wing. They're also regal, charismatic, monogamous and willing to fight to the death to protect home, mate and chicks.

Last year, Erie decapitated a younger falcon -- from Cleveland -- that attempted to claim Dorothy and the nest. There's speculation that the battle weakened him or made him vulnerable.

Ms. St. John last saw Erie last fall. He typically went on autumn excursions but failed to return. Although nests change control when a young peregrine defeats an older bird, Ms. St. John said she's seen no signs of a falcon fight. E2 likely happened upon a good situation.

"Erie's gone and doesn't come back," Ms. St. John said, setting the possible scenario. "What is [Dorothy] thinking? She can't call Erie on a cell phone and ask if he's still alive. Then there's a new guy, and what does she tell him? 'I have a mate but haven't seen him.' And he probably thought, 'I'll win her over.' "

The younger male has shown vigor in courtship rituals and is a good provider. He's also shown excitement with the eggs. "He's very attentive," Ms. St. John said. "He checks on her and brings her food."

Her blog at www.wqed.org/birdblog/ notes that she confirmed the new male by examining 4,500 photos from the "falconcam" over six weeks. E2, like Erie, has a band on his leg but the two have different coloration.

In time, Ms. St. John said she'll get the band number to identify him and where he's from.

"Dorothy is happy with E2," she said on her blog. "They have four eggs to incubate, and he's helping with incubation more than Erie did in recent years. So who are we to complain?"