The following excerpt is from the Hawk Mountain Website (PA) website (see theparagraph that I highlighted in italics):
How many feathers do hawks, eagles and falcons have?
Feathers, not flight, are the distinguishing characteristic of birds. If an animal hasfeathers, it is a bird. If an animal does not have feathers, it is not. Indeed, the telltale impressions of feathers--not the associated reptile-like bones--helped
scientists identify the more than 150-million-year-old fossilized remains ofArchaeopteryx lithographica, as those of an ancient bird.
In addition to providing a rigid airfoil for flight, feathers insulate a bird fromsummer heat and winter cold. Along with body oils, feathers help waterproof
birds, and shield their skin from dust and debris. The various colors of feathers
may serve to hide or advertise a bird's presence.
In general, birds have lots of feathers, especially around heat-sensitive areas
such as the head and neck, where upwards of 40% of a bird's feathers can befound. Larger species tend to have more feathers than smaller species. For
example, a 3- to 4-gram Ruby-throated Hummingbird (Archilochus colubris) has
about 950 feathers, compared with 25,000 for a 15- to 18-lb Whistling Swan
(Cygnus columbianus). Outside the tropics, birds tend to lose some of theirfeathers over the course of each breeding season, replacing them only in fall, justin time for winter. The number of feathers varies little among members of thesame species.
Except for detailed studies of wing- and tail-feather molt in several raptors, thenumber of feathers that each species of raptor has not been well studied. Evenso, we do know that Barred Owls (Strix varia) have about 9,200 feathers and that
Bald Eagles (Haliaeetus leucocephalus) have about 7,100. Again proving its
misnomer, 30% of a Bald Eagle's feathers are on its head! With a combined
weight of almost 700 grams, the plumage of a Bald Eagle comprises about onesixth of the bird's mass--almost three times as much as its skeleton!
Although almost all raptors are born with a relatively thin coating of downfeathers, most develop a second thicker coat of down within days of hatching.
Depending upon the species, true, fully-shafted feathers begin to appear within
10 days to 5-6 weeks, with smaller species "feathering out" more quickly thanlarger ones. By the time they are ready to fledge, young birds have acquired
most of their first year's plumage.
In most raptors, feathers cover all but small portions of the faces, feet, and toesof adult birds, but there are exceptions. Old and New World vultures, forexample, tend to have near-naked heads and necks, while only a few species
such as the Lappet-faced Vulture (Aegypius tracheliotus) of Africa and the Middle
East and the Red-headed or Pondicherry Vulture (A. calvus) of India, southern
China, and Malaysia, have heads that are entirely devoid of feathers. For manyvultures, feathers of the head and upper neck are limited to a small number ofdowny tufts, or so-called "cotton wool" feathers. Bald-headedness in vulturesappears to be associated with their propensity for poking their heads into rotting
carcasses of animals upon which they feed. Regularly banging one's headagainst decaying flesh would almost certainly soil and contaminate"unpreenable" head feathers, so sanitation is enhanced by the lack of headplumage.
By comparison, most owls are fully feathered--head, feet, and toes--and in someinstances so much so that only the bird's eyes, beaks, and talons remain
uncovered. Such full-feathering helps muffle an owl's flight as its flaps and glides
through the still night air in search of prey. Feathered feet and toes also protect
the owl against potential bites from prey. Snowy Owls (Nyctea scandiaca) haveparticularly well feathered feet and toes--useful insulation against cold arcticweather. The Rough-legged Hawk (Buteo lagopus), a tundra-dwelling diurnal
raptor, shares this adaptation. Old World fishing owls, which prey on fish in water,
have unfeathered feet and toes.
Like most birds, diurnal birds of prey have ten primary flight feathers on eachwing, along with 14 to 25 secondaries (falcons typically have 16), and 12 or 14
tail feathers. Larger species tend to have greater numbers of secondaries.
Northern Harriers (Circus cyaneus), for example, have 14; Cooper's Hawks(Accipiter cooperii) 15; Red-tailed Hawks (Buteo jamaicensis) 17; Great HornedOwls (Bubo virginianus) 14; Black Vultures (Coragyps atratus) 19; Osprey(Pandion haliaetus) 20; King Vultures (Sarcoramphus papa) 21; CaliforniaCondors (Gymnogyps californianus) 22; and Andean Condors (Vultur gryphus)
25. Bobwhite Quail (Colinus virginianus)--which spend most of their timewalking--have only 10 secondaries, while the extremely long-winged and longflighted Wandering Albatross (Diomedea exulans) has 32.
Feathers--which are an astonishingly complex extension of a bird's skin--consist
mainly of keratin, the fibrous protein that makes up human hair and nails.
Although avian anatomists have classified feathers into dozens of different types,
the typical or classic type is the "contour feather," the kind that provides theoutermost of most of the bird's body (including wing and tail feathers). Contourfeathers consist of a hollow, cylindrical shaft (the quill), from which a long seriesof sidebranches (barbs) that form the "vane" of the feather. Barbs, in turn, havetheir own series of interlocking sidebranches called "barbules," which serve toalign and hold the barbs in place along the vane. The structural complexity eachfeather is considerable. The tail feathers of Northern Harrier, for example, areestimated to have at least 1.25 million barbules each. No wonder raptors spend
so much time preening!
Many birds of prey have specialized down feathers called "powder down."
Scattered across their body, these somewhat matted feathers grow continually,
with parts breaking off into a fine powder that apparently helps absorb the grimeand debris that raptors contact.
REFERENCES
Brodkorb, P. 1955. Numbers of feathers and weights of various systems in a Bald
Eagle. Wilson Bulletin 67:142.
Burton, J. A. 1973. Owls of the world. E. P. Dutton, New York, New York, USA.
Mundy, P., D. Butchart, J. Ledger, and S. Piper. 1992. The vultures of Africa.
Academic Press, London, England
Van Tyne, J., and A. J. Berger. 1976. Fundamentals of ornithology, 2nd ed. J.
Wiley & Sons, New York, New York, USA.
Wetmore, A. 1936. The number of contour feathers in passerine and related
birds. Auk 53:159-169