leaves, stones, and sticks into a huge mound, in which they
bury their eggs. The feet of the Maleo are not nearly so
large or strong in proportion as in these birds, while its
claws are short and straight instead of being long and
much curved. The toes are, however, strongly webbed at
the base, forming a broad powerful foot, which, with the
rather long leg, is well adapted to scratch away the loose
'sand (which flies up in a perfect shower when the birds
are at work), but which could not without much labour
accumulate the heaps of miscellaneous rubbish, which
the large grasping feet of the Megapodius bring together
with ease.
We may also, I think, see in the peculiar organization of
the entire family of the Megapodidse or Brush Turkeys, a
reason why they depart so widely from the usual habits of
the Class of birds. Each egg being so large as entirely to
fill up the abdominal cavity and with difficulty pass the
walls of the pelvis, a considerable interval is required
before the successive eggs can be matured (the natives say
about thirteen days). Each bird lays six or eight eggs or
even more each season, so that between the first and last
there may be an interval of two or three months. Now, if
these eggs were hatched in the ordinary way, either the
parents must keep sitting continually for this long period,
or if they only began to sit after the last egg was deposited,
the first would be exposed to injury by the climate, or to
destruction by the large lizards, snakes, or other animals
which abound in the district; because such large birds
must roam about a good deal in search of food. Here then
we seem to have a case, in which the habits of a bird may
be directly traced to its exceptional organization; for it
will hardly be maintained that this abnormal structure
and peculiar food were given to the Megapodidse, in order
that they might not exhibit that parental affection, or
possess those domestic instincts so general in the Class
of birds, and which so much excite our admiration.
It has generally been the custom of writers on Natural
History, to take the habits and instincts of animals as fixed
points, and to consider their structure and organization as
specially adapted to be in accordance with these. This
assumption is however an arbitrary one, and has the bad
effect of stifling inquiry into the nature and causes of
“ instincts and habits,” treating them as directly due to a
“ first cause,” and therefore incomprehensible to us. I
believe that a careful consideration of the structure of a
species, and of the peculiar physical and organic conditions
by which it is surrounded, or has been surrounded in past
ages, will often, as in this case, throw much light on the
origin of its habits and instincts. These again, combined
with changes in external conditions, react upon structure,
and by means of “ variation” and “ natural selection” both
are kept in harmony.
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