PITTSBURGH (KDKA) — While four eggs were laid in the peregrine falcon nest on top of Pitt’s Cathedral of Learning, it looks like there will only be two chicks this year.

The first egg hatched on April 22, and the other two eggs quickly followed. The aviary on Monday pointed out that dedicated viewers of the Peregrine FalconCam may have noticed that the fourth egg hasn’t hatched. 

National Aviary Ornithologist Bob Mulvihill said an egg fails to hatch for several reasons. It’s possible the embryo wasn’t being successfully fertilized, there was inadequate incubation or a defect interfered with development. 

That leaves only two chicks in the nest after the third egg to hatch died last week. The aviary said the chick struggled during feedings and showed other signs that it wouldn’t survive. 

“It’s important to remember that the Peregrine FalconCam gives us a view into the wild world of birds, and while it’s not our role to intervene, we can learn a lot from studying these behaviors,” the aviary wrote in Monday’s update.

It was a sad season for Pittsburgh birdwatchers. The Hays bald eagle nest is empty this year after the couple’s single egg broke in March. The eagles in the nest at U.S. Steel’s Irvin Plant laid two eggs, but only one, named “Lucky,” hatched.

People can still watch Carla and Ecco’s other two peregrine falcon chicks grow up. They’re expected to fledge the nest in June, the aviary says.