The tufts of feathers which distinguish the short-eared and
long-eared owls, and are developed still more imposingly in
the great eagle owl of northern Europe, are, of course, no
more ears than they are horns; but the true ears of the owls
are most remarkable organs. The facial disk of feathers, which
gives them their most characteristic appearance, serves as
a kind of sounding-board or ear-trumpet to concentrate the
slightest sounds and transmit them to the orifice of the true
ear, which is concealed in the small feathers behind the eye.
Even in the barn-owl, which possesses the least complicated
arrangement of this kind, the orifice of the ear is covered by
a remarkable flap of skin; while in the other species there are
striking differences in the size and shape of this orifice and
its covering flap on the two sides of the head. The exact way
in which owls utilize this elaborately specialized apparatus
has still to be discovered; but it is a natural inference that
two ears of widely different structure must give the owls
which possess them a power of localizing sound which is of the
greatest use to them when hunting small creatures in the dark.
It is, therefore, all the more surprizing that the barn-owl’s
ears have not this difference of structure, altho the power
of instantly locating the rustle of the running mouse must be
almost indispensable. For catching small birds, which are the
especial prey of the wood-owl, keenness of sight rather than of
hearing must be necessary, since they are chiefly caught when
at roost; and the large nocturnal eye is developed in most of
the owls almost as remarkably as the ear. In the short-eared
owl, which is a day-flying species, the eye is correspondingly
reduced. It has also a far less conspicuous facial disk; and
this might also seem to be naturally explained as a result of
its diurnal habits, with the consequent reduction of the need
for acute hearing, if it were not for the marked difference in
the structure of its two ears, which is even greater than in the
case of the wood-owl. In the study of such complex problems,
we are soon forced to realize how inadequate is even the most
helpful and fascinating of single clues. The equilibrium of
nature is no simple thing, like the balance of a pair of scales;
it more resembles the complicated equipoise of an aeroplane
among air-currents playing in three dimensions.--London
_Times_.
(502)