Aves.] 



MUSEUM OF ANIMATED NATURE. 



251 



with ease, and to sail with graceful freedom in the 

 higher regions of the air. This form of wing is ex- 

 emplified in the condor : it may be observed, that 

 though the concavity of these ample wings aids in 

 soaring, it obliges the bird in descending to sweep 

 down in a series of gyrations, each circle contract- 

 ing, till the bird gains the ground. 



Where the wings are concave, as in the owl, and 

 composed of lax, soft feathers (the whole of the 

 plumage being full and downy), the flight is buoy- 

 ant, noiseless, wheeling, and differing altogether 

 in character from that of the falcon or swallow. 

 The feathers yield too much, and are too soft, to 

 produce any whistling or rushing noise in flight; 

 no rigid edges cut the air, the vanes of the quill- 

 i'eathers are lax, and the outer edge of the first, 

 instead of being plain, is fringed with a line of short 

 lashes (the prolonged terminations of the plumelets 

 composing the vane), as if to guard against the least 

 possibility of sound being produced by the winnow- 

 ing of the air. 



Concavity of wing, joined with shortness and 

 roundness, is unfavourable to flight. Birds with 

 this form of wing are for the most part terrestrial in 

 their habits ; their bodies are heavy, and their great 

 powers reside in the legs : the common fowl or the 

 turkey are examples in point. There are, however, 

 such modifications among terrestrial birds in the 

 structure of the wings as to render some far superior 

 in flight to others" The wings of the common 

 partridge, for instance, are short, round, and con- 

 cave, and its flight is necessarily short, whirring, and 

 destitute of ease ; but, on the other hand, the quail, 

 its immediate ally, in consequence of a somewhat 

 more lengthened and pointed form of the pri- 

 maries, possesses, if not great, at least tolerable 

 powers of flight, and is one of our birds of pas- 

 sage. 



As illustrations of wings, Fig. 1145 represents that 

 of the common Grosbeak ; Fig. 1146, that of the 

 Chaffinch ; Fig. 1147, that of the common Sparrow ; 

 Fig. 1148, that of the Magpie ; Fig. 1149, that of the 

 Chinese Jacana, in which the primaries have narrow 

 plumose appendages at the tips. 



With respect to the wings of the sparrow, gros- 

 beak, and chaffinch, it will be observed that their 

 form is moderately pointed; still, however, the 

 flight of these birds is not remarkable for velocity ; 

 for, in the first place, the extent of wing does not 

 bear that comparative relationship to the size of 

 the body which it does in the falcon, vulture, or 

 swallow ; and in the second place, the quill-feathers 

 are destitute of firmness, the shafts are weak, and 

 the vanes are soft and flimsy ; while at the same 

 time the primaries but little exceed the secondaries, 

 so that the breadth of the extended wing is half, or 

 more than half, of its length. 



The crow and rook have ample and moderately 

 pointed wings ; the first quill-feather is much 

 shorter than the second and third, these being ex- 

 ceeded by the fourth, which is the longest : they 

 are firm and elastic. The flight of these birds is 

 steady, and they sail with ease, often at a very great 

 elevation : and sometimes perform a series of rapid 

 evolutions, wheeling, diving, and as suddenly re- 

 ascending. Allied to the crow and rook (Corvus), 

 the magpie differs materially from them in its 

 mode of flight, and in the figure and proportion of 

 its wings. The wing of the magpie is short and 

 rounded ; the first quill-feather is narrow, and about 

 half the length of the second ; the fourth and fifth, 

 which are nearly of equal length, are the longest in 

 the wing. " Magpies and jays," says White, " flut- 

 ter with powerless wings, and make no despatch." 

 The flight of the magpie is supported by short 

 quick strokes. 



Some birds have appendages of various kinds to 

 their wings, the uses of which cannot well be ac- 

 counted for. In the Chinese jacana, for instance, 

 the tips of the primaries are furnished with slender 

 narrow plumes or appendages. In some of the 

 night-jars we have a singular development of 

 plumes. In the Leona night-jar, from the 

 midst of the wing-coverts issues a long elastic 

 shaft to the extent of twenty inches, and tipped for 

 about five inches with a broad web. In another 

 species, from Sierra Leone, the ninth quill-feather 

 is produced to an amazing extent, running narrower 

 as it proceeds, and is soft and flowing. In many 

 birds the tertiajs are produced into pendent plumes 

 of great length, which fall gracefully down and 

 almost touch the ground, as we see in the Demoi- 

 selle and the Stanley cranes. The tertials of the 

 common crane also form elegant plumes, each fea- 

 ther drooping with dishevelled barbs: the tertials 

 of the sacred ibis are also produced into lax plumes. 

 In the egret the scapularies are elongated into 

 wavy plumes, the feathers having their vanes com- 

 posed of long filamentous plumelets or barbules 

 distant from each other. In the cranes, herons, 

 egrets, &c, the wings are long and ample. 



Some birds, as we have observed, are very infe- 

 rior in flight to others, their wings being modified 



accordingly; but there are not only birds incapable 

 of easy and graceful progress through the air, but 

 there are some which are utterly destitute of the 

 power of flight, even in its lowest degree. There 

 are two conditions of wing connected with the want 

 of this power: first, that in which the wing is 

 simply undeveloped, both as respects osseous struc- 

 ture, muscles, and feathers — as in the ostrich, cas- 

 sowary, &c. ; secondly, that in which the wing is 

 converted into an organ of aquatic progression — 

 as in the great auk, but more particularly in the 

 penguin, which has its paddle-like wings fur- 

 nished with close, minute, rigid feathers resembling 

 scales. 



From the leading modifications exhibited in the 

 wings of birds, we turn to those presented by the 

 tail, the osseous structure of which, with the mode 

 in which the feathers are ordinarily arranged, has 

 already been pointed out. Even more numerous 

 than those of the wings are the diversities of form 

 and size presented by this organ ; diversities more 

 or less directly influencing the character of the 

 flight. In some instances the tail is reduced to a 

 mere rudiment, or is even wanting, and in others it 

 is large and of great length. Nor is it only from its 

 form or size that the tail of the feathered race 

 influences the peculiar manner of flight ; the tex- 

 ture and quality of the feathers themselves are of 

 great importance. Where the tail consists of soft 

 plume-like feathers, we may at once set it down 

 that the bird thus furnished is ill adapted for aerial 

 progression ; and it will be found, moreover, that 

 the structure of the wings and the nature of the 

 general plumage will invariably correspond with the 

 characters of the tail ; for wings well calculated for 

 aerial progression, and a tail unadapted for it, would 

 be a violation of the laws of Nature, there being no 

 contradiction of parts and purposes in her ways, 

 On the contrary, if the feathers of the tail be firm 

 and the barbs close— though the tail itself may not 

 be very ample — it will be of great avail. There 

 are many examples of birds with small tails being 

 endowed with surprising powers of flight ; indeed in 

 most birds of rapid flight, the wings, when closed, 

 advance with their points to the end of the tail, or 

 even pass beyond it : we may mention the peregrine 

 falcon and the swift; in the latter bird the tail 

 feathers are only ten in number, and are far ex- 

 ceeded by the wings when closed. Where, how- 

 ever, the tail is much reduced, as in the kingfisher, 

 its rudder-like power is evidently diminished, and 

 though the flight may still be rapid, it is necessarily 

 straight and arrow-like, there being no power of 

 sailing in easy circles, or of making abrupt turns 

 and doubles, as we see in the kite on the one hand, 

 and in the swallow on the other. 



We need hardly say that in the act of flying birds 

 expand their tails, and thus the extent of surface is 

 increased to their manifest advantage. Where the 

 wings are ample, and the tail ample at the same 

 time, the flight is easy and graceful ; where the tail 

 is short and the wings long and vigorous, the flight 

 is generally rapid and impetuous; but where the 

 tail is long and ample, and the wings rounded and 

 short, as in the magpie, the flight is laborious. The 

 principal forms assumed by the tail are as follows : — 

 1, square, or even; 2, rounded; 3, graduated regu- 

 larly (every feather advancing in due degree), or 

 irregularly (some advancing to an extreme beyond 

 the others) ; 4, slightly forked with rounded points : 

 5, more or less deeply forked with acute points; 6, 

 plumose. 



The size of the tail varies under every modifica- 

 tion of form, and the forms themselves differ to a 

 considerable degree, as it regards a very great num- 

 ber of minute particulars ; the feathers also com- 

 posing the tail exhibit an infinity of differences, 

 both in form and texture. 



As examples of some of the principal forms in the 

 tail of birds we select the following illustrations :— 

 Fig. 1150, the tail of the Kestrel spread out ; Fig. 

 1144, the tail of the common Buzzard; Fig. 1151, 

 the tail of a species of Humming-bird; Fig. 1152, 

 the tail of the Heron; Fig. 1153, the tail of the 

 Sandpiper ; Fisr. 1154, the tail of the Coot ; Fig. 

 1155, the tail of the Pied Wagtail; Fig. 1156, the 

 tail of the Magpie; Fig. 1157, the tail of the 

 Chaffinch; Fig. 1158, the tail of the Lark; Fig, 

 1159, the stiff rudder-like tail of the Cormorant; 

 Fig. 1160, the scansorial tail of the Tree-creeper. 



Having thus spoken of the arrangement of 

 the feathers, which, it may be added, the bird 

 moults and renews at certain seasons, we proceed to 

 explain the. different parts of a feather itself. A 

 feather consists of a stem (scapus), divided into the 

 barrel or hollow base (calamus), in which the 

 nutrient vascular pulp was originally contained, and 

 which remains shrivelled as a pith; the shaft 

 (rachis), and the web or vane on each side (pogo- 

 nium), which consists of numerous barbs (radii 

 pogoniorum) closely interlocked (at least usually) 

 by means of minute processes called barbules 

 (radioli). In many feathers the base of the web 



consists of loose, free, soft barbs ; and there is fre- 

 quently an accessory plume at the base of the 

 shaft, generally a downy tuft, but sometimes almost 

 as much developed as the feather from which it 

 emanates, as in the emu, in which bird each feather 

 seems double, with one barrel. 



There is no external auditory apparatus, but the 

 orifice to the internal auditory apparatus is covered 

 with a tuft of close feathers ; sometimes, however, as 

 in the owl, there are external membranous valves, 

 capable of being opened or closed at will. The 

 sense of hearing is acute. The jaws of birds are 

 invested with a horny sheath, forming a beak dif- 

 ferently modified in different groups. In the par- 

 rots the upper jaw (or mandible) is articulated to 

 the skull in such a manner as to be freely move- 

 able. 



In many birds the base of the upper mandible is 

 clothed with a tough skin called the cere, in which 

 the nostrils are placed, but the situation of these 

 greatly varies. Between the base of the beak and 

 the eye a naked space called the lore (brum) often 

 intervenes. 



With respect to the eye of birds, we may observe 

 that the bony orbits are capacious, and the organs 

 seated therein of according magnitude. In birds 

 of -prey the general shape of the eye is that of a bell,, 

 or chalice ; the cornea, which is very convex, forms 

 the bottom of the chalice ; the posterior segment of 

 the sclerotica its cover. This peculiar form (see 

 Fig. 1162) arises from the curvature and length of 

 the bony plates, which, as in all other birds, occupy 

 the front of the sclerotica, lying close together and 

 overlapping each other. These bony plates form a 

 flat or slightly convex ring ; but in the rapacious 

 birds they form a concave ring, which gives to the 

 eyeball the above-mentioned form. By means of 

 this ring the eye becomes a kind of self-adjusting 

 telescope, so as to take in both near and very distant 

 objects. 



A representation of the sclerotic plates forming 

 the bony ring in the eye of the penguin (Apteno- 

 dytes) is represented at Fig. 1161. They remind us 

 forcibly of the eye-plates in some of the reptiles, 

 particularly of those belonging to the eyes of the 

 Enaliosaurians, or fossil marine lizards. The pen- 

 guin has to adjust, its eye for vision both on land 

 and under water. This contrivance must greatly 

 assist the adjustment necessary for seeing clearly in 

 such different media. 



The crystalline humour is fiat in birds ; and the 

 vitreous humour is very small. The colour of the 

 iris varies in different species, and in many cases is 

 very brilliant. The marsupium, which arises in the 

 back of the eye, and the use of which is not very 

 clearly ascertained, is a peculiarity in the eye of 

 birds. They have three eyelids, two of which, the 

 upper and lower, are closed in most of the race by 

 the elevation of the lower one, as may be frequently 

 seen in our domestic poultry. The owl, the goat- 

 sucker, and a few others have the power of depress- 

 ing the upper eyelid. Of these birds the upper 

 only is furnished with eyelashes generally : the 

 ostrich, secretary vulture, some parrots, and a few 

 other birds have them in both lids. But the third 

 eyelid, or nictitating membrane, forms the most 

 curious apparatus. When at rest, this, which is a 

 thin semi-transparent fold of the tunica conjunctiva, 

 lies in the inner corner of the eye, with its loose 

 edge nearly vertical. By the combined action of 

 two muscles which are attached towards the back 

 of the sclerotica, it is capable of being drawn out 

 so as to cover the whole front of the eyeball like a 

 curtain, and its own elasticity restores it to the 

 corner in which it rested. This, it is said, enables 

 the eagle to look at the sun : it may be seen in 

 operation to much advantage in the Great South 

 American Eagle (Harpyia destructor) at the gar- 

 dens of the Zoological Society in the Regent's 

 Park. 



Fig. 1162 shows the section of the eye of the owl* 

 a, the quadrangular bony scale within the substance 

 of the sclerotic, giving it firmness ; b, an expansion 

 called the ciliary body, extending over the whole of 

 the inner surface ; c, a curious membrane, called the 

 pecten, projecting through the choroid into the 

 vitreous humour, and in some birds attached to the 

 side of the lens : of its use little is known. Fig. 

 1163 shows the orbit turned so as to expose the 

 recti and other muscles. Fig. 1164 shows the pos- 

 terior view of the eyeball; Fig. 1165 a lateral view 

 of the same. The'se show the two muscles which 

 originate from the sclerotic, and are applied to its 

 curved surface round the entrance of the optic 

 nerve (Fig. 1164, a). The larger represents rather 

 more than half of what if completed would be a 

 broad circular ring (Fig. 1164, b) : it is called the 

 quadratus. Attached by its wider edge, near the 

 margin of this part of the sclerotic, its fibres con- 

 verge to the narrower edge, and terminate in a nar- 

 row tendon (Fig. 1164, c), perforated through its 

 whole length like the hem of an apron. The 

 second smaller muscle, called the pyramidalis, from 



2K2 



