I can recall only one sighting of an owl in nature, not at a zoo. My story is typical, according to Marianne Taylor in her beautiful book Owls. Since owls are nocturnal and are masters of camouflage, many people never see owls and are unaware of the species in their area. You must be skilled to see owls, unless you are lucky enough to have a barn owl in your barn.
You can start honing your owl spotting skills with Taylor's book, which is filled with incredible photos showing the birds in their natural habitats. Most are composed so you see the owls right away, but there were a few that I had to study a bit to see the owls, even when they were big and right in the center of the image. Their feathers mimic bark very effectively.
While almost every page has a photo or two and some of them are full page photos, Owls is more of a reference book than photo book. In the first half, Taylor describes the avian families that can be defined as owls, telling how they live, hunt, court, nest, and grow. She details threats to owl survival and recounts owls from legends and literature. In the second half, she profiles 41 species that can be found in Europe or North America. Some of these species only skirt the eastern edge of Europe and live mainly in Asia or Africa, so the Himalayan wood owl, Ural owl, and Asian barred owl are included.
My favorite photo in Owls might be the Northern saw-whet owl (page 202), though I really like the snowy owl (page 128), too. What is your?
Taylor, Marianne. Owls. Cornell University Press, 2012. 224p. ISBN 9780801451812.