Birds normally make up only a small percent of the diet. Barn owls, like many other birds, swallow prey whole. The excellent night vision of owls is well known, but there are circumstances in nature when even the visual adaptations of owls would not be able to detect small, concealed prey. Relatively recently it was discovered that barn owls can locate and capture prey acoustically, allowing them to take prey in very dark conditions or under vegetation and snow.2 The silent flight of owls, also well known to most people, must now be reevaluated in terms of the owl's auditory prey detection. Long thought to be useful in preventing the owl's prey from hearing the approaching predator, it is now believed that quiet flight may be at least as useful in preventing interference with the owl's own hearing for prey detection.
Barn owls are rather sedentary birds and no truly migratory populations are known.
There is, however, a dispersal of young owls shortly after they become independent of their parents. Records from banded barn owls show that this many occur in any compass direction and may range from a few to over a thousand miles in distance. Having completed their dispersal, barn owls select a home range and usually remain there for the rest of their lives. The first few months after independence from the parents are also the most hazardous-about 70 percent of all barn owls die in this period. Even though most have a rather short life, the oldest known wild barn owl lived almost 18 years and some have survived 20 years in zoos.