FIFTEEN STORIES above Center City streets, Arthur F. McMorris held a 21-day-old falcon in front of him and wedged a finger into the bird's screeching mouth.

The bird's mouth looked healthy, its eyes bright and its talons strong. The only problem was that the chick and its three sisters were crawling with mites.

For McMorris, peregrine falcon coordinator for the Pennsylvania Game Commission, the fix was simple - a bit of insecticide powder and the nestling would be on its way.

The check-up was part of a banding process held yesterday in the City Hall tower, an event led by the game commission for the past five years.

The bands are used to track the birds, which are on the state's endangered species list, as they make their way around the city, McMorris said. Philly houses seven pairs of peregrine falcons, or about 15 percent of the 43 pairs in the state, including two birds that live in the Ben Franklin Bridge, McMorris said.

"One in every five peregrine falcons that we've banded in Pennsylvania, we've seen later on and that's an excellent rate," he said.

Before the birds could be inspected, a hard hat wearing McMorris had to wade out onto the ledge where the birds nest, carefully dodging the swoops of their watchful, aggressive mother, to bring them inside. Looking on was Donald Perelman, a game commission volunteer, who first spotted the baby birds hatching from a live camera feed at his dentist's office on Chestnut Street near 24th.

"Everytime I go to my dentist, I check the camera and there's never anything there," Perelman said. "Until this one time a couple weeks ago, and I'm like, 'wow!'"

Perelman has since taken hundreds of photos of the fledglings and posted them on the City Hall falcons Facebook page. He and his coworkers, who watch the falcons from their office on South Broad Street, have attended the banding several times.

The newest batch of chicks is part of a long lineage of peregrine falcons that began nesting at City Hall as far back as 1940. The manmade nest they currently live in was set up in 1991, and the falcons came and went intermittently until 2011. Since then, the birds have returned each year, McMorris said.

Peregrine falcons were once on the federal list for endangered animals, but are now only considered endangered in Pennsylvania, McMorris said. Philadelphia's tall buildings, bridges and ledges, that act as artificial cliffs, have created an environment suitable for the fastest bird in the world, he said.

"Once they nest in a particular spot, they're there again year after year after year," McMorris said. "They don't mess with success."