The daily morning journal and courier. [volume] (New Haven, Conn.) 1894-1907, 1895-07-24
Animal Vision.

Birds are commonly credited with an
extraordinary range Of vision, Cireum-
stances lend aid to the development of
the mental factors in their case. The
usual distance e. waieh terrestrial
species use their eyes is limited by the
ground horizon. But In the case of the
soaring birds, such as vultures and
eagles, the horizon, the natural limit of
sight, is enormously extended. Mac
gillivray early noted that though birds
of prey have orbits Of great size-the
eyeball of the common buzzard being
one and one-eighth inches in diameter
they do not, as rule, soar when seek
Ing their prey. The eagle, when hunt
Ing, flies low, just as do the sparrow
hawk and the hen-harrier.
Yet the vultures and condors, birds
which admittedly do soar when seeking
food, have been proved to find carrion
by sight A carcass was covered with
canvas and some offal placed upon it.
The vultures saw this, descended and
ate 1t, and then sat on the covered por-
ton within few inches of a putrid
carcass. When hole was made In the
covering they saw and attacked the
food below. But the rapid congrega-
ton of yultures from a distance to a
carcass, Is probably due to their watch
ing their neighbors, each of which is
surveying a limited area. Charles Oar
win pointed out that in a level country
the height of the sky commonly noticed
by mounted man is not more than 10
degrees above the horizon; and a vul-
ture on the wing at the height of be-
tween 5000 feet and 1000 feet would
probably be two miles distant, and IN
visible Those which descend rapidly,
and appear to have come from beyond
the range of human sight, were perhaps
lowering vertically over the hunter
when he killed his game.
There remains one undoubted In
stance In which bird-vision is Ear
keener than that of man. The great
gray shrike, Lanlus excubitor, Is habit
ually used by the men who catch fall
cons at Valhenswaard to give notice of
| the approach of a hawk. The bird sees
| 1t far sooner than the man, and at once
gives notice of its approach. This Is a
single instance in which the specialized
aeuteness of sight may be due to the
fact that the bird in question much re-
sembles in color the pigeons, which are
| the falcons favorite food But long
sight does not seem a common property
of bird-vision. The gannsts which
catch fish at sea, descend from a con-
sidera BILE height, but they kill theil
prey on the surface of the water or neal
| it. Nocturnal birds and animals
| though able to see with little light
have no enhanced powers when the
light is more powerful; and those AMI.
mails which, like deer, feed by night OF
day indifferently, have only developed
a keenness Of vision from constant feai
and vigilance. Horses and cattle
which have the same power of sight by
night, have never Increased their vtsua
range. Dogs habitually rely on another
4 sense, that Of scent in preference to
| their eyes, and win walk over a dead
bird while their brain is intent on dis
| covering It's place by scent alone.
| Weasels, when hunting, will run UP to
| a human being who initiates the squeak
of rabbit and peer up at him to dis
cover whence the sound comes from.
The smallness Of the eye limits its