Peregrine falcons on Pitt's Cathedral of Learning lay first egg of season

The peregrine falcons nesting on top of Pitt's Cathedral of Learning have laid their first egg of the season.

The National Aviary, which runs a livestream of the nest, said Carla laid the first egg around 4 a.m. on Wednesday. It's the first of up to six, though the average peregrine falcon clutch is four. 

She'll likely lay an egg every 48 hours until her clutch is complete. The aviary said viewers will know she's almost done because she'll start incubating after laying the second-to-last one. Until then, peregrine falcon eggs can endure the whiplash temperatures of spring, so they're safe to be left uncovered. Ecco will also help with incubation, taking up the job about a third of the time.

It comes after a record number of six peregrine falcons were counted in Allegheny County during the annual Audubon Christmas Bird Count. It's a big bounce back from the early 1960s, when there weren't any peregrine falcons nesting in the entire state of Pennsylvania because of the use of DDT. After the harmful pesticide was banned in 1972, conservation efforts have helped the species rebound. 

Scientists now monitor the species' population through citizen science projects like the Christmas Bird Count and by banding the chicks. Last year, the Pennsylvania Game Commission banded three chicks born in the nest on Pitt's Cathedral of Learning. The year before that, two chicks were banded.