The Owl is a minor antagonist of the book Stellaluna and main antagonist of the 2004 animated adaptation.
In the book, he sets the plot off by attacking Stellaluna and her mom, causing the former to fall out of her mothers' grasp into the forest below
The owl has a much larger role in the animated film adaptation. This owl is very different than the one in the book. He is credited as "Great White Owl" and is voiced Blu Mankuma. He serves as a threat to not only Stellaluna, but also to the sparrow family and the rest of the forest as well. Stellaluna & the baby birds constantly run into him and he threatens "Who dares go there?", but they always manage to escape.
Near the climax, he kidnaps Momma bird and plans to eat her, but Stellaluna leads the other bats to attack the owl, and he flies away in terror, never to bother anyone again.