Spirit of the age. [volume] (Woodstock, Vt.) 1845-1913, 1895-11-23
ANIMAL VISION.
Only One Bird Whose Sight Is BETTER
Than That of Man.


Than That of Man.
Birds arc commonly credited with
an extraordinary range of vision.
Circumstances lend aid to tho devcl-
opment of the mental factors in
their case. The usual distance at
which terrestrial species use their
eyes is limited by tho ground hori-
ION. But in the case of the soaring
birds, such as vulturcs and eagles,
tho horizon, tho natural limit of
sight, is enormously extended.
Macgillivray early noted that,
though birds of prey have orbits of
great size-tho oyoball OF tho COM
mon buzzard being Is inches in
Misunderstanding do not, as rule,
soar when seeking their prey. Tho
eagle when hunting flies low, just
as do the sparrowhawk and the hen
barrier.
Yet tho vultures and condors,
birds which admittedly do soar when
seeking food, have boon 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 tho covered portion
within a few inches of II 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 distance
to a carcass is probably due to their
watching their neighbors, each Of
which is surveying limited area.
Charles Darwin pointed out that i'll
a level country tho height of sky
commonly noticed by a mounted
man is not moro than Is degrees
above tho horizon, and vulture on
the wing at tho height of between
5000 feot and 1000 feet would prob
ably be two miles distant and invis.
ible. Those which descend rapidly
and appear to have como from be-
You'd the range of human sight were
perhaps lowering vertically over tho
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 shriEe, Lanius eXcubitor, is
habitually used by the men who
catch falcons at Valliensward to give
notice of the approach of u hawk.
Tho bird sees it far sooner than tho
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 tho pigeons which are tho
falcon favorite food. But long
sight does not seem common proper
ty of bird vision. The gannets,
which catch fish Mt sea, descend from
considerable height, but they kill
their prey on the surface of tho wa.
ter or near it. Nocturnal birds and
animals, though able to SEQ with lit
tic light, have no enhanced powers
when the light is more powerful,
and those animals which, like deer,
feed by night or day indifforently
have only developed a keenncss 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 dead bird while their
brain is intent Oh discovering its
place by scent alone. Weasels when
hunting will run up to human be.
ing who initiates the squeak of q
rabbit and peer up at him to discov-
OF 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 DO
the best organ of sight, and in tho
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 bo
proportionately limited. - London
Spectator.