These images by Hong & Cheng a.k.a. catspace show a Spotted Wood Owl (Strix seloputo) indulging in its comfort behaviour. This includes it stretching a wing and a leg, usually one side at a time (above left). Then it preened its feathers to keep them in top condition (above right). Those feathers around the head area where the bill has no access, the owl has to use its feet to scratch (left).
Here, scratching is direct, done by raising its foot from under its wing, characteristic of terrestrial birds, as seen in the Red-breasted Parakeet (Psittacula alexandri), also in the Grey Nightjar (Caprimulgus indicus). Among aboreal birds, on the other hand, scratching is indirect. The leg is extended over the wing to reach the head, as in Barn Swallow (Hirundo rustica).
Hong & Cheng