The following singular fact was first brought into public notice by
Mr. Yarrel; and will be found in his papers in the second volume of the
_Zoological Journal_. The fact alluded to is, that there is attached to
the upper mandible of all young birds about to be hatched a _horny
appendage_, by which they are enabled more effectually to make
perforations in the shell, and contribute to their own liberation. This
sharp prominence, to use the words of Mr. Yarrel, becomes opposed to the
shell at various points, in a line extending throughout its whole
circumference, about one third below the larger end of the egg; and a
series of perforations more or less numerous are thus effected by the
increasing strength of the chick, weakening the shell in a direction
opposed to the muscular power of the bird; it is thus ultimately enabled,
by its own efforts, to break the walls of its prison. In the common fowl,
this horny appendage falls off in a day or two after the chick is hatched;
in the pigeon it sometimes remains on the beak ten or twelve days; this
arises, doubtless, from the young pigeons being fed by the parent bird
for some time after their being hatched; and thus there is no occasion
for the young using the beak for picking up its food.--_Ibid_.
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