The plumage of owls is adapted in several ways. Being mainly nocturnal, owls have no need to display visually and so their markings are normally mottled shades of black, brown and grey, patterned to conceal them during the daytime from possible predators and other birds which might mob them. The snowy owl, although distinctive with its white plumage, blends perfectly with the arctic snow which is often still on the ground when the female is incubating her eggs. The Barn Owl’s plumage may appear more puzzling. If viewed from above, the most likely direction from attack whilst hunting over its favourite habitat of long rank grassland with its brown dead stems of long grass, it almost disappears from sight as it does in its original nesting sites in sandstone cliffs. The white under-parts may make it less visible against the sky when it hunts in daylight which it does when food is in short supply or when there are chicks in the nest.
The ear tufts possessed by some species are just feathers and nothing to do with the ears. They can be used as camouflage, by breaking up the owls outline and their posture communicates their mood.
Most owls have a defensive posture which is used to intimidate potential enemies. It varies from species to species but usually involves the wings being spread out around the body with the head lowered down and the feathers fluffed up. This all gives the impression that the owl is much bigger and when accompanied by “bill clicking”, hissing and swaying the body from side to side is normally enough to drive off most predators.
The feathers on owls’ wings have several unique features. Firstly, they have a downy up per surface, which reduces the noise as they move over each other as the wing beats. Secondly the outer primaries have a stiff comb like fringe on their leading edge which modifies the airflow over them as they cut through the air which reduces noise. Finally, on the trailing edge of the wing, the feathers have a soft hair like fringe, which reduces air turbulence behind the wing. The net result of these modifications is totally silent flight even at ultrasonic level which means that prey are not forewarned of attack and the bird can use its amazing hearing at its best without the noisy wing beats possessed by other birds. Also the plumage of owls is very thick and downy, retaining vital body heat when hunting at night. This makes owls look allot larger than they actually are. Most owls are deceptively light for their size, also most have quite large and broad wings, which with the low body weight gives them a very low wing loading which is why their flight is so buoyant and moth like. This allows them to fly at a very low speed, which improves the chances of locating prey, and it also lets them carry quite heavy loads back to the nest or roost.
The thick soft plumage insulates the owl whilst it is exposed to cold night time temperatures, and in most species (certainly all northerly species) the leg feathers extend right down to the feet and sometimes over the toes as well.
A White Faced Owl's static defense display.