CHAR. The basal portion of the bill covered by a soft skin, in which
are situated the nostrils, overhung by an incumbent fleshy valve, the
apical portion hard and convex. The hind toe on the same level with the
rest; the anterior toes without membrane at the base. Tarsi more or less
naked; covered laterally and behind with hexagonal scales.
The bill of the _Columbidæ_ is always shorter than the head, thinnest in
the middle; the basal half covered by a soft skin; the apical portion
of both jaws hard; the upper one very convex, blunt, and broad at the
tip, where it is also somewhat decurved. There is a long nasal groove,
the posterior portion occupied by a cartilaginous scale, covered by a
soft cere-like skin. The nostrils constitute an elongated slit in the
lower border of the scale. The culmen is always depressed and convex.
The bill is never notched in the true Doves, though _Didunculus_ shows
well-defined serrations. The tongue is small, soft, and somewhat fleshy.
The wing has ten primaries, and eleven or twelve, rarely fifteen,
secondaries; the latter broad, truncate, and of nearly equal length. The
tail is rounded or cuneate, never forked.
The tarsus is usually short, rarely longer than the middle toe,
scutellate anteriorly, and with hexagonal plates laterally and behind;
sometimes naked. An inter-digital membrane is either wanting entirely,
or else is very slightly indicated between the middle and outer toes.
The valuable monograph of Bonaparte in the second part of _Conspectus
Avium_ renders the task of arranging the American _Columbidæ_ in
proper sequence and of determining their synonomy comparatively easy.
He divides the family into _Lopholæminæ_, _Columbinæ_, _Turturinæ_,
_Zenaidinæ_, and _Phapinæ_, the second and fourth alone occurring in
North America. They may be briefly distinguished as follows:—
=Columbinæ.= Tarsus shorter than the lateral toe; feathered above.
=Zenaidinæ.= Tarsus longer than the lateral toes; entirely bare of
feathers.