For all his majesty, Louie was not much taller than a folded newspaper. He alighted on his nest at the Gulf Tower Wednesday and glared through an office window. Then, standing near two lonely eggs, he turned his head and chirped to the sky.
"He's calling her," said Ann Hohn, who works at the Make-A-Wish Foundation, on the other side of the glass. The Make-A-Wish employees daily watch the Gulf Tower's peregrine falcons, and for years, the only birds they have known were Louie and his mate, Tasha 2.
But on March 20, Tasha 2 disappeared. She has since been replaced by a new female, Dori. Louie remained, as did Tasha 2's recently laid eggs, which Louie incubates fitfully as he courts his new love interest.
It has been a two-week melodrama, staged 37 floors above the city and scripted by a community of devoted followers. The threads of the story are classic: an aging mother ousted from her home, a victorious upstart discovering her new life, a dutiful male shuttled between partners.
"We make up all sorts of conversations that have nothing to do with reality," said Ms. Hohn.
The local bird-lovers who watch the nest's 24-hour webcam know that Dori's ascent is the natural order of things. Tasha 2 was at least 14 years old: ancient by peregrine standards.
"She was elderly," said Kate St. John, a WQED employee who blogs about the city's falcons.
Still, Tasha 2's fans cannot help but hurt for her.
"Our theory is that she just said 'To heck with this!' and went to Florida," said Ms. Hohn. "She's not dead. She's retired."
The reality, like many things about the story's characters, is only partly understood. What is known is this:
America's peregrine falcon population, once severely thinned by exposure to the pesticide DDT, has been slowly replenishing.
In 2009, there were 25 "active nesting pairs" in Pennsylvania, said Dan Brauning, wildlife diversity chief for the state Game Commission. Louie and Tasha 2 were one of four pairs in the Pittsburgh area, where peregrine falcons have successfully mated at the Gulf Tower since 1991.
Tasha 2 arrived at the man-made nest in 1998. She raised dozens of chicks there with two mates. (Louie replaced Boris after a bloody 2003 coup.)
"She had a good long run of it," said Mr. Brauning.
Her reproductive capacity was diminishing, though. Some of the eggs she laid in recent years did not hatch, said Todd Katzner, the National Aviary's director of conservation and field research.
Meanwhile, Dori was migrating from her Ohio birthplace. The 3-year-old bird was first observed and identified in October 2009, near the 62nd Street Bridge.
"Presumably what happened is that she was scouting around, looking for greener pastures," said Dr. Katzner. "She saw this territory at the Gulf Tower that was occupied by a bird that she thought she could displace."
From there, any story is speculative, he said: "We don't know what happened to Tasha 2. What we do know is that Tasha 2 had laid two eggs in the nest box and then suddenly disappeared."
Ms. St. John, who regularly watches the webcam, said she had noticed Tasha 2 looking nervous recently, and late March 19, the bird began to wail ceaselessly.
"The wailing call can mean many things," said Ms. St. John. "It can mean 'Come here.' It can mean 'Go away.' "
When dawn arrived, Louie returned to the nest and tried to court his mate. Instead, Tasha 2 immediately left.
The next time she appeared on camera, said Ms. St. John, "feathers were flying off of her." Her wing drooped, the sign of an old injury she usually hid. She appeared only once more.
That evening, Louie began the rituals of a new courtship, bowing to an unseen bird. Finally, Dori arrived and they bowed together.
Since then, Dori has mostly ignored Tasha 2's eggs. Dr. Katzner said it is theoretically possible that the eggs will hatch, but that most likely, Dori will soon lay eggs of her own.
Falcon fanatics watching the webcam this week have seen Dori and Louie courting furiously.
"We are trying to figure out what they're up to," said Ms. St. John. "The peregrine people, oh my gosh. We're all crazy," she laughed.
Wednesday, Ms. Hohn spoke lovingly of watching chicks hatch in years past. She said she was shocked when Tasha 2 disappeared.
"We just felt that she would fight off anyone," she said, as Louie appeared in the window.
A few minutes later, with Dori nowhere in sight, he swooped away.
Vivian Nereim: firstname.lastname@example.org or 412-263-1413.