[5] The bird's head and upper body typically vary between pale brown and some shade of grey (especially on the forehead and back) in most subspecies.

The beak varies from pale horn to dark buff, corresponding to the general plumage hue, and the iris is blackish brown.

The barn owl has been successfully introduced into the Hawaiian island of Kauai in an attempt to control rodents; however, it has been found to also feed on native birds.

Outside the breeding season, males and females usually roost separately, each one having about three favoured sites in which to conceal themselves by day, and which are also visited for short periods during the night.

Hairlike extensions to the barbules of its feathers, which give the plumage a soft feel, also minimise noise produced during wingbeats.

[3]: 47–61 The diet of the barn owl has been much studied; the items consumed can be ascertained from identifying the prey fragments in the pellets of indigestible matter that the bird regurgitates.

On a rocky islet off the coast of California, a clutch of four young were being reared on a diet of Leach's storm petrel (Oceanodroma leucorhoa).

[8] Locally superabundant rodent species in the weight class of several grams per individual usually make up the single largest proportion of prey.

Its legs and toes are long and slender which improves its ability to forage among dense foliage or beneath the snow and gives it a wide spread of talons when attacking prey.

On bird-rich islands, a barn owl might include some fifteen to twenty percent of birds in its diet, while in grassland it will gorge itself on swarming termites, or on Orthoptera such as Copiphorinae katydids, or true crickets (Gryllidae).

The facial disc plays a part in this process, as is shown by the fact that with the ruff feathers removed, the bird can still locate the source in azimuth but fails to do so in elevation.

[12] Hunting nocturnally or crepuscularly, this bird can target its prey and dive to the ground, penetrating its talons through snow, grass or brush to seize small creatures with deadly accuracy.

In arid regions, breeding may be irregular and may happen in wet periods, triggered by temporary increases in the populations of small mammals.

The actual dates of egg-laying vary by year and by location, being correlated with the amount of prey-rich foraging habitat around the nest site and often with the phase of the rodent abundance cycle.

In colder climates, in harsh weather and where winter food supplies may be scarce, they may roost in farm buildings and in barns between hay bales, but they then run the risk that their selected nesting hole may be taken over by some other, earlier-nesting species.

Single males may establish feeding territories, patrolling the hunting areas, occasionally stopping to hover, and perching on lofty eminences where they screech to attract a mate.

[13] Once a pair-bond has been formed, the male will make short flights at dusk around the nesting and roosting sites and then longer circuits to establish a home range.

At later stages of courtship, the male emerges at dusk, climbs high into the sky and then swoops back to the vicinity of the female at speed.

When the female has reached peak weight, the male provides a ritual presentation of food and copulation occurs at the nest.

By three weeks old, quills are starting to push through the skin and the chicks stand, making snoring noises with wings raised and tail stumps waggling, begging for food items which are now given whole.

The male is the main provider of food until all the chicks are at least four weeks old at which time the female begins to leave the nest and starts to roost elsewhere.

Barn owls are particularly dependent on their ability to fly quietly and manoeuvre efficiently, and in temperate areas their prolonged moult lasts through three phases over a period of two years.

[18] Unusually for such a medium-sized carnivorous animal, the barn owl exhibits r-selection, producing large number of offspring with a high growth rate, many of which have a relatively low probability of surviving to adulthood.

[19] While wild barn owls are thus decidedly short-lived, the actual longevity of the species is much higher—captive individuals may reach twenty years of age or more.

The most significant cause of death in temperate areas is likely to be starvation, particularly over the autumn and winter period when first year birds are still perfecting their hunting skills.

In northern and upland areas, there is some correlation between mortality in older birds and adverse weather, deep-lying snow and prolonged low temperatures.

Collision with road vehicles is another cause of mortality, and may result when birds forage on mown media strips and shoulders.

In Handbook of Birds of the World Volume 5: Barn-owls to Hummingbirds, the following subspecies are listed:[6] Curącao barn owl - sometimes considered a separate species.