CHAR. Eyes directed forward, and surrounded by a radiating system of
feathers, which is bounded, except anteriorly, by a ruff of stiff,
compactly webbed, differently formed, and somewhat recurved feathers;
loral feathers antrorse, long, and dense. Plumage very soft and lax,
of a fine downy texture, the feathers destitute of an after-shaft.
Oil-gland without the usual circlet of feathers. Outer webs of the
quills with the points of the fibres recurved. Feathers on the sides
of the forehead frequently elongated into ear-like tufts; tarsus
usually, and toes frequently, densely feathered. Ear-opening very
large, sometimes covered by a lappet. Œsophagus destitute of a dilated
crop; cœca large. Maxillo-palatines thick and spongy, and encroaching
upon the intervening valley; basipterygoid processes always present.
Outer toe reversible; posterior toe only about half as long as the
outer. Posterior margin of the sternum doubly indented; clavicle weak
and nearly cylindrical, about equal in length to the sternum. Anterior
process of the coracoid projected forward so as to meet the clavicle,
beneath the basal process of the scapula. Eggs variable in shape,
usually nearly spherical, always immaculate, pure white.
The Owls constitute a very natural and sharply limited family, and
though the species vary almost infinitely in the details of their
structure, they all seem to fall within the limits of a single
subfamily.
They have never yet been satisfactorily classified, and all the
arrangements which have been either proposed or adopted are refuted by
the facts developed upon a close study into the true relationship of
the many genera. The divisions of “Night Owls,” “Day Owls,” “Horned
Owls,” etc., are purely artificial. This family is much more homogeneous
than that of the _Falconidæ_, since none of the many genera which I
have examined seem to depart in their structure from the model of
a single subfamily, though a few of them are somewhat aberrant as
regards peculiarities in the detail of external form, or, less often,
to a slight extent, in their osteological characters, though I have
examined critically only the American and European species; and there
may be some Asiatic, African, or Australian genera which depart so far
from the normal standard of structure as to necessitate a modification
of this view. In the structure of the sternum there is scarcely the
least noticeable deviation in any genus[7] from the typical form. The
appreciable differences appear to be only of generic value, such as a
different proportionate length of the coracoid bones and the sternum,
and width of the sternum in proportion to its length, or the height
of its keel. The crania present a greater range of variation, and, if
closely studied, may afford a clew to a more natural arrangement than
the one which is here presented. The chief differences in the skulls of
different genera consist in the degree of pneumaticity of the bones,
in the form of the auricular bones, the comparative length and breadth
of the palatines, and very great contrasts in the contour. As a rule,
we find that those skulls which have the greatest pneumaticity (e.g.
_Strix_ and _Otus_) are most depressed anteriorly, have the orbital
septum thicker, the palatines longer and narrower, and a deeper
longitudinal median valley on the superior surface, and _vice versa_.
The following classification is based chiefly upon external characters;
but these are in most instances known to be accompanied by osteological
peculiarities, which point to nearly the same arrangement. It is
intended merely as an artificial table of the North American genera,
and may be subjected to considerable modification in its plan if exotic
genera are introduced.[8]
Genera and Subgenera.
=A.= Inner toe equal to the middle in length; inner edge of middle
claw pectinated. First quill longer than the third; all the quills
with their inner webs entire, or without emargination. Tail
emarginated. Feathers of the posterior face of the tarsus recurved, or
pointed upwards.
1. =Strix.= No ear-tufts; bill light-colored; eyes black;
tarsus nearly twice as long as middle toe; toes scantily
haired. Size medium. Ear-conch nearly as long as the height of
the skull, with an anterior operculum for only a portion of
its length; symmetrical.
=B.= Inner toe decidedly or much shorter than the middle; inner edge
of middle claw not pectinated. First quill shorter than the third; one
to six outer quills with their inner webs emarginated. Tail rounded.
Feathers of the posterior face of the tarsus not recurved but pointed
downwards.
I. Nostril open, oval, situated in the anterior edge of the cere,
which is not inflated.
_a._ Cere, on top, equal to, or exceeding, the chord of the
culmen; much arched. Ear-conch nearly as long as the height of the
skull, with the operculum extending its full length; asymmetrical.
2. =Otus.= One or two outer quills with their inner webs
emarginated. With or without ear-tufts. Bill blackish; iris
yellow. Size medium.