From Hawks Aloft

Still not too big to snuggle with dad! As you can tell, a couple of the babies are nearly the same size as Bubba, our resident Great Horned Owl (far right). Right now we can tell the difference based on the fluffy plumage, but luckily for us, another telltale sign for Bubba, is that he likes to keep his ear tufts-which are actually called plumicorns-tucked close to his head.

Despite the term "ear tufts" plumicorns are not in fact ears, which are asymmetrical holes covered by feathers inside the facial disc. Plumicorns are feather tufts that stick out over their head and are believed to be used for communication, camouflage, and possibly intimidation!