The length of a bird's life very much depends on the care which is taken
of it. There are some parrots which have lived more than a century; and
nightingales, chaffinches, and goldfinches have been known to live more
than twenty-four years in a cage. The age of house birds is so much the
more interesting, as it is only by observing it that we can know with
any degree of certainty the length of birds' lives in general. Thus
house birds are of importance to the naturalist, as giving him
information which he could not otherwise acquire. It is worthy of
remark, that the quick growth of birds does not prevent their living
much longer than quadrupeds. The length of life with these is estimated
to be six or seven times longer than the time which they take to grow:
while birds live fifteen, twenty, and even thirty times longer.
This length of life is sometimes attributed to the substance of which
the bones are composed being much more loose and light, and consequently
remaining porous longer than those of quadrupeds. Some swans have lived
three hundred years.