A Barn Owl Centre in Gloucester has had an owl named Kaln since 1996 that arrived as a chick.  It was determined to be a male because "he" always had the hallmarks of a male bird, so imagine the center's surprise when Kaln laid an egg after 23 years.  Staff plan to change Kaln's name to Kalnee, since the discovery.  The egg wasn't fertilized so won't develop into a chick.  The charity has 46 birds they care for, mostly birds of prey.  Twenty-three years, they say she still acts like a teenager, so there is that.