Adult females have a reputation for making a "wac-wac" call when alarmed around the nest (a type of double squawk that is also described as "barking.") We only observed it a precious few times last year in the owlets, and honestly, the first time I heard it I was certain it was something other than an owl. I had no idea an owlet could or would make this vocalization.
Ruby made the same call today at about 12:40 PM, so we have good color video of her doing it. Perhaps the owlets make more different types of vocalizations when there aren't adults around to make them instead.
The International Owl Center advances the survival of wild owl populations through education and research. We plan to accomplish our mission through biological and cultural programs and displays, green building design, citizen-science and other research, international exchange of information, the World Owl Hall of Fame, the International Festival of Owls, and other means.