The owl haunts ruins and flies only at night; preferring to live in darkness it hides from the light. It is a dirty, slothful bird that pollutes its own nest with its dung. It is often found near tombs and lives in caves. Some say it flies backwards. When other birds see it hiding during the day, they noisily attack it to betray its hiding place. Owls cry out when they sense that someone is about to die. Owls fight with crows; they compete in stealing each other's eggs, the crow during the day and owl at night.

Some manuscripts say the young owls return to care for their elderly parents, something more commonly said of the hoopoe.

There are several kinds of owls described in the bestiaries and in encyclopedias: noctua or niticorax, the night-owl (also called the night-raven) that lives in the walls of ruined houses and shuns the light; the bubo, the horned owl, a dirty bird that pollutes its nest; and the screech owl (ulula, strix) that hoots to indicate sorrow.

The owl in general represents the Jews, who showed that they preferred darkness to light when they rejected Christ.

Hrabanus Maurus says that the owl signifies those who have given themselves up to the darkness of sin and those who flee from the light of righteousness.

While the owl is usually given a negative interpretation, the Aberdeen Bestiary provides a (mostly) positive moralization for the night-owl (nicticorax). "In a mystic sense, the night-owl signifies Christ. Christ loves the darkness of night because he does not want sinners - who are represented by darkness - to die but to be converted and live. ... The night-owl lives in the cracks in walls, as Christ wished to be born one of the Jewish people... But Christ is crushed in the cracks of the walls, because he is killed by the Jews. ... Christ shuns the light in the sense that he detests and hates vainglory. ... In a moral sense, moreover, the night-owl signifies to us not just any righteous man, but rather one who lives among other men yet hides from their view as much as possible. He flees from the light, in the sense that he does not look for the glory of human praise."

The flesh of the owl helps those who have been paralyzed.