Owl Feather Identification: Comb, Barring and the Law

An owl's outermost primary carries a row of stiff, curved barb tips projecting forward from the leading edge, called the leading-edge comb. A 2021 study in the Biological Journal of the Linnean Society found it on the anterior edge of the outermost primary, P10, and on the neighbouring P9, P8 and P7 in some species, as well as on the alula in the 56 species sampled.

The same study measured serration length at four points along the comb and found lengths ranging between zero and about six millimetres across the species it sampled. Pygmy owls, which are small and primarily diurnal and hunt by sight, essentially lack the structure; fishing owls of the genera Ketupa and Scotopelia turned out to have moderate combs despite earlier claims to the contrary.

So a feather with a fine comb along one edge is an owl feather, and a feather without one may still be an owl feather if it came from an inner primary, a secondary or the tail.

Owl flight feathers are broad and soft, with a loose, almost furry texture, and the vane does not hold together as tightly as a duck's or a hawk's. The pattern is usually mottled and crosswise-barred in browns, buffs and grays, which matches the plumage of the birds: the Great Horned Owl has horizontal bars across the belly, the Barred Owl has horizontal bars on the chest and vertical stripes on the belly, and the Long-eared Owl has stripes rather than bars below.

Color varies within a species as well as between them. The Eastern Screech-Owl comes in gray, reddish and brown morphs, so a small barred feather in any of those colors fits the same bird. The American Barn Owl runs to cinnamon and gray above with white to buff below and small black spots.

Place the feather on the bird before guessing the species: primaries have pointed tips, secondaries rounded or squared ends with often-curved shafts, and the two central tail feathers are symmetrical with a straight shaft. Then measure it in millimetres and compare against the scans in the USFWS Feather Atlas, which covers 438 North American species and gives feather and vane lengths for each scan.

The Linnean Society study tested competing explanations and found support for both the stealth hypothesis, that quiet flight keeps prey from hearing the owl, and the self-masking hypothesis, that it keeps the owl's own flight noise from drowning out the sounds it is listening for.

The evidence for the second is a correlation: facial disk size went with comb size across species, which the authors read as owls with good hearing also tending to have quiet flight. That fits the pattern at the other end too, since the primarily diurnal pygmy owls that hunt visually are the ones that essentially lack the comb.

This is why an owl feather feels different in the hand from a hawk feather of the same length. The structure that makes it quiet also makes it soft.

Owls are native North American birds, so their feathers are covered by the Migratory Bird Treaty Act. The USFWS Feather Atlas states that possession of feathers and other parts of native North American birds without a permit is prohibited, and that there is no exemption for molted feathers or for feathers taken from road-killed or window-killed birds.

The exceptions listed are the feathers of legally hunted waterfowl and other migratory gamebirds, and use by Native Americans. Institutions and individuals wanting feathers, bones or whole specimens for education or research must apply for permits.

The practical approach is to photograph and leave. Lay the feather down as you found it, put a ruler or coin alongside the shaft in the same frame, shoot straight down on a plain contrasting background, and take a second frame of the other face. If the feather is attached to a dead bird, do not handle the bird bare-handed; use gloves or a bag, wash your hands afterwards, report unusual numbers of dead birds to your state wildlife agency, and see a doctor if you become unwell.

A Great Horned Owl feather is large, soft and mottled in browns, buffs and grays with dark crosswise bars, and if it is an outer wing feather it carries the owl's comb of stiff barb tips on the leading edge. Size is the second check. Wikipedia gives a wing chord of 297-400 mm and a tail of 175-252 mm, so the longest primaries usually fall in the Feather Atlas's huge class (over 24 cm) and tail feathers in its large to huge range (16 cm and up). A soft, barred feather that size in North America points to a Great Horned Owl or one of the other big owls.

Color depends on where you are. Wikipedia describes subarctic birds as a washed-out light buff, Pacific Coast birds as dark brown with blackish blotching, and desert birds as a pale dusky buff with indistinct barring. A pale feather from Arizona and a dark one from Washington can both be from this species.

• Great Horned Owl body feathers: barred crosswise, matching the horizontal bars across its belly.
• Barred Owl body feathers: a belly feather with a lengthwise stripe fits a Barred Owl, which has horizontal bars on the chest but vertical stripes on the belly.
• Red-tailed and other hawks: similar size and brown barring, but the vane is firmer and smoother and there is no leading-edge comb. See the hawk feather page.
• Tiny downy feathers: the legs and feet of a Great Horned Owl are fully feathered, and Wikipedia says its foot feathers are the second-longest known in any owl after the Snowy Owl. Small fluffy feathers under a roost tree may be from the feet or body.

Wikipedia lists three wing features behind its quiet flight: serrated leading edges, soft feathers that deaden sound, and fringes on the trailing edge. Run a fingertip along both edges: an owl feather's trailing edge feels fringed rather than clean.

The USFWS Feather Atlas identification tool asks five things in order, and for a suspected Great Horned Owl feather the answers are usually:

• Pattern: barred or mottled.
• Color: brown.
• Size: large (16-24 cm) or huge (over 24 cm); the Atlas's other classes are small, up to 8 cm, and medium, 8-16 cm.
• Position: primary, secondary or tail, if you can tell; the leading-edge comb means an outer primary.
• Bird type: owls.

Compare the scanned reference feathers side by side with yours, looking at the spacing of the bars and the color of the tip.

Less rare than many people think. Audubon estimates about 5.7 million Great Horned Owls and says they live in practically every North American habitat, from swamps and deserts to northern conifer forest near treeline, including towns. They also nest very early, beginning in late winter in the north (Audubon). A large barred feather under a big tree, in a park, or on a trail is a reasonable find almost anywhere on the continent.