EXTERNAL PARTS OF BIRDS.—THE WINGS. 111 
they are more alike and less distinctly disposed in rows or series; so that for practical purposes 
they pass under the general name of under wing-coverts, or lining of the wing. Since, when 
the wing is particularly marked on the under side, it is the coverts and not the remiges that are 
highly or variously colored, the common expression ‘‘ wing below,” or “ under surface of the 
wing,” refers to the coverts more particularly. We should distinguish, however, from the under 
coverts in general, the axillars, or axillary feathers (Lat. axilla, the arm-pit). These are the 
innermost feathers lining the wings, lying close to the body; almost always longer, stiffer, 
narrower, or otherwise peculiarly modified. In ducks, for example, and many of the waders, 
as snipe and plover, they are remarkably well developed. The color of the axillaries is the 
principal distinction between some species of plovers. The 
Remiges, or Flight-Feathers (fig. 30, b, s, and ¢),give the wing its general character, 
mainly determining both its size and its shape; they represent most of its surface and of its 
inner and outer borders, and all of its posterior outline, forming a great expansion of which the 
bony and fleshy framework is insignificant in comparison. The shape of the wing is indeed 
primarily affected by the relative lengths of its bony segments, the upper arm being, in a 
humming-bird, for example, very short in comparison with the terminal portion of the limb, 
and in an albatross again, both upper and forearm being greatly lengthened ; still in any case 
it is the Hight-feathers that mainly determine the coutour of the wing, by their absolute degree 
of development, their lengths proportionately to one another, and their individual shapes. They 
collectively form a thin, elastic, flattened surface for striking the air, quite firm along the front 
border where the bone and muscle lie, thence growing more mobile and resilient toward the 
posterior border and along the outer edge. Such surface may be quite flat, as in such birds as 
cut the air with long, pointed wings, like oar-blades ; but it is generally a little concave under- 
neath and correspondingly convex above ; such arching or vaulting of the wing-surface being 
usually associated with a short, broad, rounded wing, as in the gallinaceous tribe, and being 
least in birds which have the thinnest and sharpest wings. Corresponding differences in the 
mode of flight result. The short, rounded wing confers a powerful though labored flight for 
short distances, usually accompanied by a whirring noise resulting from the rapidity of the 
wing-beats; birds that fly thus are almost always thickset and heavy. The long, pointed 
wing gives a noiseless, airy, skimming flight, indefinitely prolonged, and accomplished with 
more deliberate wing-beats ; birds of this style of wing are generally triin and elegant. These, 
of course, are merely generalizations of the extremes of modes of flight, mixed and gradated 
in every degree in actual bird-life. Thus the humming-bird, which has sharp, thin wings, 
whirs them fastest of all birds, —so rapidly that the eye cannot follow the strokes, merely 
perceiving a haze about the bird while the ear hears the buzzing. The combination of acute- 
ness and concavo-convexity is a remarkably strong one, conferring a rapid, vigorous, whistling 
flight, as that of a duck or pigeon, or the splendid hurtling of a faleon. An ample wing, as 
one both long and broad without being pointed is called, is well displayed by such birds as 
herons, ibises, and cranes; the flight may be strong and sustained, but is rather slow and 
heavy. The longest-winged birds are found among the swimmers, particularly the pelagic 
family of the petrels, and some of the whole-webbed order, as pelicans, particularly the frigate- 
pelican. The last named, Tachypetes aquilus, has perhaps the longest wings for its bulk of 
body of any bird whatever, as well as the shortest feet. The American vultures are likewise 
of great alar expanse in proportion to their weight. The shortest wings, among birds possess- 
ing perfect remiges, occur among the lower swimmers, as auks and divers, and among some 
of the Galline. The great auk is, or was, perhaps the only flightless bird with well-formed 
flight-feathers, only too small to subserve their usual purpose; though certain South American 
ducks are said to be in similar predicament. In the penguins, the whole wing-structure is 
degraded, and the remiges abort in scale-like feathers, the wings being reduced to fins both 
