ntil it is again capable of facing enemies, and of
seizing food with its claws, which have become hard again. This
seclusion appears to last a month. Here is, then, an example of a
temporary dwelling rendered necessary by special conditions of defect
for external life. We are here still in the infancy of the art.

Speaking generally, birds are accomplished architects. Certain of them
are, however, content with a rudimentary cavern. There is no question
here of those who retire to clefts in the rock or in trunks of trees,
for in these cases the cavity is only the support of the true house,
and it is in the construction of this that the artist reveals his
talent. I wish to speak of animals which remain in a burrow without
making a nest there. A Parroquet of New Zealand called the _Kakapo_
(_Strigops habroptilus_) thus dwells in natural or hollowed
excavations. It is only found in a restricted portion of the island
and leads a miserable life there, habitually staying in the earth and
pursued by numerous enemies, especially half-wild dogs. It tries to
hold its own, but its wings and beak do not suffice to protect it, and
the race would have completely disappeared if these birds were not
able to resist, owing to the prudence with which they stay within
their dwellings. They profit by a natural retreat, or one constructed
in rocks or beneath roots of trees; they only come out when impelled
by hunger, and return as soon as they can in case of danger.

A large number of animals also hollow out shelters for their eggs,
with the double object of maintaining them at a constant temperature
and of concealing them. Most reptiles act in this manner. The way in
which a Tortoise, the _Cistudo lunaria_, prepares its nest is
extremely curious. When the time for this labour arrives, the tortoise
chooses a site. It commences by boring in the earth with the end of
its tail, the muscles of which are held firmly contracted; it turns
the tail like a gimlet and succeeds in making a conical hole.
Gradually the depth of the hole becomes equal to the length of the
tail, and the tool then becomes useless. The _Cistudo_ enlarges the
cavity with the help of its posterior legs. Using them alternately it
withdraws the earth and kicks it away, then piles up this rubbish on
the edge of the hole, arranging it so as to form a circular rampart.
Soon the posterior members can take nothing more from the too distant
bottom. The moment for laying has now come.