On May 20, the four peregrine falcon chicks living at the top of the Cathedral of Learning — the third brood for resident falcon pair Carla and Ecco — were banded and given a clean bill of health.

This 25th season signifies a quarter-century of partnership among the University of Pittsburgh, the Western Pennsylvania Conservancy, the Pennsylvania Game Commission and the National Aviary.

When Kate St. John, a longtime birder, first noticed peregrine falcons courting around the Cathedral in 2001, she brought the organizations together to install a nest box ahead of the next mating season. That’s when the cliff-dwelling falcons made their home on the towering building, tucking into the safety of the nest box waiting for them on the 40th floor. Since then, nearly 70 chicks have fledged the nest, a major step for conservation and research efforts across the region.

“The University is a good landlord to the peregrines, making sure their nest site does not suffer human intrusion which would cause them to abandon the [Cathedral],” said St. John, who also runs the blog, Outside My Window, which monitors peregrine falcons and other regional birds.

Due to the use of the pesticide DDT, peregrine falcon populations dropped to critical lows in the 1950s and 60s, landing them on Pennsylvania’s Endangered and Threatened Species list in 1961. It was only five years ago that the species was removed from the list, thanks to dedicated conservation efforts.

Banding is an important part of that work, allowing researchers to collect data on each bird’s lifespan and breeding rate, as well as how far it travels from where it hatched.

The three-week-old chicks were give a weightless aluminum bands on each leg — one is stamped with a unique code that identifies the chicks for the Bird Banding Laboratory, a scientific program managed by the U.S. Geological Survey, and the other displays an alphanumeric code that allows observers to tell the chicks apart.