Despite being nocturnal animals, owls have their not-so-dark side. In addition to their association with death, they're also seen as symbolizing wisdom, which is kind of ironic in that several studies (including one performed by the UCLA Department of Psychology, available via eScholarship) indicate they're not terribly bright. The whole "wise old owl" trope actually comes from the ancient Greeks — owls were associated with the goddess Athena (via Redlands Daily Facts) and therefore took on some of her second-hand wisdom despite not having too much of their own.
With the Greeks, this link to a goddess also meant that owls were seen as lucky, with soldiers convinced that a sighting of Athena's messenger would bring them luck in battle. In Mongolia and Japan, owls are also seen as lucky, and in the latter country you can even visit an owl cafe. Pellets Inc. points out that white owls in particular are often interpreted as bringing good fortune, as legends tell of white owls saving people from natural disasters. As to why white owls are seen as good omens, this may be due to their comparative rarity in southern climates, with snowy owls seldom being seen south of Michigan. Symbolism aside, though, owls actually do bring luck in the form of pest control. They keep down the rodent population and also eat insects, so if you do hear a hoo, don't be afraid. Instead, you can rest assured that "owl" is well.
