The Marietta journal. [volume] (Marietta, Ga.) 1866-1909, 1895-09-26
AN.AlAl- AiSiON.
Only One Bird Whose Sight Is Better
Than That nj Man,

Than That III Man.
Birds are commonly credited with
an extraordinary range of vision.
circumstances lend aid to the devel-
Opment Of the mental factors in
their case. The usual distance at
which terrestrial species use their
eyes is limited by the ground hori-
2on. But in the case of the soaring
Birds, such as vultures and eagles,
the horizon, the natural limit Of
sight is enormously extended.
Macgillivray early noted that,
though birds of prey have orbits of
great size-the eyeball of the COM
mon buzzard being 1 1-8 inches in
diameter-they do not, as a rule,
soar when seeking their prey The
eagle when hunting flies low, just
as do the sparrowhawk and the hen
barrier.
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 it and
then sat on the covered portion
within few inches of putrid car
cass. When hole was made in the
covering, they saw and attacked the
food below. But the rapid congre-
cation of vultures from a distance
to carcass is probably due to their
watching their neighbors, each of
which is surveying a limited area.
Charles Darwin pointed out that in
a level country the height of sky
commonly noticed by mounted
man is not more than Is degrees
above the horizon, and a vulture on
the wing at the height of between
5000 feet and 1900 feet would prob
ably be two miles distant and inyis-
ible. Those which descend rapidly
and appear to have come from be-
yond 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 far
| keener than that of man. The great
gray shrike, Lanius excubitor, is
habitually used by the men who
catch falcons at Valliensward to give
notice of the approach of hawk.
The bird sees it far sooner than the
men, and at once gives notice of it's
approach. This is single instance
in which the specialized aouteness
of sight may be due to the fact that
the bird in question much resembles
in color the pigeons which are the
| falcons favorite food. But long
sight does not seem common proper
ty of bird vision. The gannets,
which catch fish at sea, descend from
considerable height, but they kill
their prey on the surface of the wa
ter or near it. Nocturnal birds and
animals, though able to see with lit
tie light, have no enhanced powers
when the light is moro powerful,
and those animals which, like deer,
! feed by night or day indifferently
have only developed a keenness of
vision from constant fear and Wig
lance. Horses and cattle, which
have the same power of sight by
night, have never increased their
visual range. Dogs habitually rely
on another sense, that of scent, in
| preference to their eyes and will
walk over d dead bird while their
brain is intent on discovering its
| place by scent alone. Weasels when
hunting will run up to a human be-
ing who initiates the squeak of a
rabbit and peer up at him to discov-
er where the sound comes from.
The smallness of the eye limits its
powers. Just as the best telescope
has usually the largest object glass,
so the largest eye will probably be
the best organ of sight, and in the
absence of any extraordinary devel-
opments in the size of the organ
itself in animals their power of Wis
| ion must, in the absence of evidence
to the contrary, be supposed to be
proportionately limited. - London
Spectator.