The Descent of Man

Fig. 43. Outer tail-feather of Scolopax javensis.]
In the foregoing cases sounds are made by the
aid of structures already present and otherwise
necessary; but in the following cases certain
feathers have been specially modified for the
express purpose of producing sounds. The
drumming, bleating, neighing, or thundering
noise (as expressed by different observers) made
by the common snipe (Scolopax gallinago)
must have surprised every one who has ever
heard it. This bird, during the pairing-season,
flies to "perhaps a thousand feet in height," and
after zig-zagging about for a time descends to
the earth in a curved line, with outspread tail
and quivering pinions, and surprising velocity.
The sound is emitted only during this rapid
descent. No one was able to explain the cause
until M. Meves observed that on each side of
the tail the outer feathers are peculiarly formed
(Fig. 41), having a stiff sabre-shaped shaft with
the oblique barbs of unusual length, the outer