PITTSBURGH (KDKA) — The National Aviary has announced some sad news about their Andean Condor pair.

Lianni and Lurch’s egg has stopped developing. The Aviary says it is an “unfortunate, but not uncommon occurrence.”

The Aviary announced Lianni had laid an egg just last month, on the condor’s 36th birthday.

They say Lianni is a special bird, overcoming a life-threatening illness in 2012. She went through a blood transfusion, which had never been done on a condor.

She now requires heart medication and regular checkups, but is living as a condor normally would.

While the Aviary says they are disappointed with the outcome, they are hopeful for the future.

The Aviary says in a press release, “This egg, though it did not successfully hatch, is a promising sign for Lianni and Lurch. We are very hopeful for their future breeding success.”

Last year, the pair’s chick died shortly after hatching.