770 
ORNITHOLOGY 
thers lying clofe by each other, when fpread, no part of 
them can mifs its impulfe upon the air. 
As the llender fubltance of feathers is apt to bedifcom- 
pofed by accident, or the exceffive heat or moifture of the 
atmofphere, nature has made an extraordinary provifion 
for their adjuftment, and prefervation in a proper tempe¬ 
rament. Of this, Goldfmith has given the following 
very accurate account: The animal is furniflied with a 
gland behind, containing a proper quantity of oil, which 
can be prefled out by the bird’s bill, and laid fmoothly 
over every feather that wants to be drefled for the occa- 
fion. This gland is fituated on the rump, and furnifned 
with an opening or excretory duft; about which grows a 
finall tuft of feathers, femewhat like a painter’s pencil. 
When therefore the feathers are {battered or rumpled, 
the bird, turning its head backward, with the bill catches 
hold of the gland, and, prefling it, forces out the oily 
fubltance, with which it anoints the disjointed parts of 
the feathers; and, drawing them out with great afliduity, 
replaces them in due order; by which they unite more 
clofely together. Such poultry, however, as live for the 
moll part under cover, are not furnilhed with fo large a 
{lock of this fluid as thofe birds that refide in the open 
air : the feathers of a hen, for inftance, are pervious to 
every fliower; on the contrary, fwans, geefe, ducks, and 
all fucEi as nature has directed to live on the water, have 
their feathers drefled with oil from the firffc day of their 
leaving the {hell. Thus their fcock of fluid is equal to the 
neceflity of its confumption : but their fleih contrails a 
flavour from it, which renders it in fome fo very rancid 
as to make it utterly unfit for food ; however, though it 
injures the flefli, it improves the feathers for all the do- 
meftic purpofes to which they are ufually converted. 
All the external parts of birds appear to be formed for 
rapidity of motion in that element they are deftined to 
inhabit; all contribute to facility of efcape : the ftiape 
and lightnefs of the body, its covering of feathers, the 
large fize of the wings, and the force of thofe mufcles by 
which they are moved. From the combined operation of 
thefe qualities, their fwiftnefs far exceeds that of the rein¬ 
deer or horfe, the fleeteft among quadrupeds ; and they can 
alfo continue their exertions for a much longer time than 
can be done by the llrongeft quadruped. Our fwifteft 
horfes are fuppofed to goat the rate of a mile infomewhat 
lefs than two minutes ; and there is one inftance on record 
of a horfe that went at the rate of nearly a mile in one 
minute, but only for one fecond of time. In fuch cafes 
an uncommon degree of exertion has been attended with 
its ufual confequences, debility, and a total want of 
power to continue that exertion ; but the motions of 
birds are not impeded by fimilar caufes, and they not only 
glide through the air with a quicknefs fuperior to that of 
the fwifteft quadrupeds, but can continue on the wing 
with equal fpeed for a conflderable length of time. Now, 
if we can fuppofe a bird to go at the rate of only half a mile 
in a minute for the fpace of twenty-four hours, it will, 
in that time, have gone over an extent of more than 700 
miles ; and, if aided by a favourable current of air, there 
is reafon to believe that it will perform the fame journey 
311 a much fliorter fpace of time. ; and, according^, M. de 
Buft'on relates a dory from fir Edmund Scot, of a hawk 
fent from the Canaries to the duke of Lerma, which re¬ 
turned from Andalulia to the ifland of Tenerifle in fif¬ 
teen hours, a fpace of two hundred and fifty leagues. 
When we proceed to examine the ftrudhire of the or¬ 
gans of fight, we find that they are no lefs adapted to the 
purpofe of celerity. In all birds, except the nocturnal 
ones, the head is fmaller in proportion to the body than 
that of quadrupeds ; their eyes, too, are more flat and 
deprefied, that they may the more eafily divide the air, 
and make way for the body. In comparing the fenfe of 
fight, in this clafs, with that of quadrupeds, it is found 
more quick, diftinft, and extepfive; and the apparent 
exception of owls is rather a confirmation of this fail, 
as the dimnefs of their fight arifes from the extreme fenfi- 
bility of the organ ; a mark of its perfection. The eyes 
of fowls feem indeed more induftrioufly laboured by the 
hand of nature than thofe of other animals. Though 
outwardly they appear final], yet, both' taken together, 
they are larger than the brain ; whereas, the orbit of the 
human eye is not the twentieth part of the brain. Ana- 
tomifts have, befides, obferved a particular expanfion of 
the optic nerve in this organ of birds, which renders the 
impreflions of external objects more vivid and diftinft. 
To protect the eye, and perhaps moderate its extreme 
fenfibility, it is poflefled of a militating membrane, with 
which it can inftantaneoufly cover the pupil of the eye, 
when the eye-lids are open. From fuch a ftrudlure of the 
eye, the fenfe of feeing in birds is greatly fuperior to 
that of other animals. Nature, having deftined them for 
rapid motion, has wifely provided for their fafety, by the 
acutenefs of that fenfe which directs it. To the fame ve¬ 
locity of movement had {he joined dullnefs of fight, 
thefe qualities would have been contrary and incompa¬ 
tible ; had the animal availed itfelfof the former, itmuft 
have been dallied to pieces by unforefeen refiftances, from 
the imperfection of the latter. Add to this, that acute¬ 
nefs of fight feems necefiary for procuring this animal’s 
fupport: an hawk, accordingly, from a height in the iky 
at which it is fcarcely perceptible by the human eye, per¬ 
ceives a lark upon the ground, and darts upon it with un¬ 
erring precifion. See Phil. Tranf. 1795. Part II. p.263. 
and the Medical Journal, vol. xxix. p. 481. 
It has been already obferved, that all birds want the 
external ear; they are furnifhed indeed with apertures, 
which convey founds into the auditory canal. Their fenfe 
of hearing is very acute, as may be conceived from their 
power of fong, and of modulating the voice, and from 
the readinefs with which they repeat founds, and learn to 
pronounce words. This faculty the bounty of nature 
has conferred upon them as an additional mean of fecu- 
rity. Surrounded as they are by man, and other tribes 
of hoftile animals, their fafety greatly depends, while in 
darknefs, or amidft the thick groves, on being duly ap- 
prifed of their approach by the quicknefs and fenfibility 
of this organ. 
Buffon is of opinion, that feveral of the quadrupeds are 
fuperior to birds in the fenfe of fmelling: in many 
of the latter, however, it is extremely delicate and acute. 
The raven and the vulture wind their prey at an immenfe 
diftance, and perhaps furpafs the dog or the fox : nor are 
we to imagine that thofe birds who have no external 
apertures in the bill are deprived of this fenfe, which 
may be communicated by the entrance of the effluvia at 
the mouth. It is remarked by Goldfmith, that, in decoys 
where ducks are caught, the men who attend them uni- 
verfally keep a burning turf near their mouths, left the 
fowl ftiould fmell their breath, and confequently fly 
away. The univerfality of this practice puts the neceflity 
of it beyond a doubt, and proves the extreme delicacy of 
the fenfe of fmellingin this fpecies of the feathered creation. 
Notwithftanding this perfection of their fenfes, birds 
fall as far fliort of quadrupeds in fagacity and intelli¬ 
gence as they are diltinguilhed by thele particulars 
above infeCls and fifties, the l'anks of animated beings 
immediately below them. 
As birds are deftined to move through the light me¬ 
dium of air, they are far inferior both in weight and mag¬ 
nitude to the quadrupeds : the largeft bird, the oftrich, 
bears no proportion to the elephant, nor does the hum¬ 
ming-bird, which nature has placed at the other extre¬ 
mity of this clafs, nearly approach to the fize of a moufe. 
Nature, as the approaches near the confines of each clafs, 
confers more and more of the properties of the adjoining 
one on each fpecies, till at laft they fo nearly approximate, 
that fhe feems doubtful in her operations. The oftrich, 
placed at the extremity of the birds, feems in many re- 
fpeCls nearly allied to a fuperior order: feemingly covered 
with hair, and incapable of fight, he makes near ap¬ 
proaches to the race of quadrupeds 5 while the finall hum¬ 
ming- 
