A window pane and a dead pigeon are all that separate John Faherty from a pair of eyasses – baby peregrine falcons – perched on a ledge outside the 11th floor of the Mercantile Building on Walnut Street. A baby peregrine falcon practices flying outside of John Faherty's office at the themercantilelib. Inside, the library is mostly quiet. Portraits of past presidents greet guests, sculptures watch over rows of books. The stillness breaks only when mother Juliet soars past the window, squawking. It's Faherty's cue to leave and let the babies eat in peace. "When there's babies, they just start circling around, and I like to think it's because I'm their favorite person," said Faherty, executive director of the Mercantile Library. "I'm fairly certain I'm their least favorite person. They're just always flying, and in every picture, they are glaring at you." Six years ago, he and staff noticed falcons nesting in the abandoned building next door. Fascinated, they took pictures of the birds...