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believe, that the young thus reared would be apt to follow by inheritance the occasional and aberrant habit of their mother, and in their turn would be apt to lay their eggs in other
nests, and thus be
in rearing their young. By a continued process of this nature, I believe that the strange instinct of our cuckoo
→OMIT
has
generated. ↑
It has, also, recently been ascertained on sufficient evidence, by Adolf Müller, that the cuckoo occasionally lays her eggs on the bare ground, sits on them, and feeds her young. This rare event is probably a case of reversion to the long-lost, aboriginal instinct of nidification. |
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| It has been objected
→OMIT
that I have not noticed other related instincts and
→adaptations of structure
in the cuckoo, which are
spoken of as necessarily co-ordinated. But in all cases, speculation on
instinct
→known to us only in
a single species, is useless, for we have
→hitherto had no
facts to guide us. Until
recently the instincts of the European and of the non-parasitic American cuckoo alone were known; now, owing to Mr.
observations, we
something about three Australian species, which lay their eggs in other
nests. The chief points
→to be referred to
are three:
that the
with rare exceptions, lays only one egg in a nest, so that the large and voracious young
ample food. Secondly, that the
remarkably
→OMIT
not
of the skylark,—a
→a bird about one-fourth as large as
the
→the small size of the egg
is a real case of adaptation we may infer from the fact of the non-parasitic American cuckoo laying
→full-sized eggs.
that the young cuckoo, soon after birth, has the instinct, the strength, and a properly shaped back for ejecting its foster-brothers, which then perish from cold and hunger.
has been boldly
→called a beneficent arrangement,
in order that the young cuckoo may get sufficient food, and that its foster-brothers may
→they had
acquired much
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| Turning now to the Australian species; though these birds generally lay only one egg in a nest, it is not rare to find two and even three eggs
the same
→OMIT
In the Bronze cuckoo the eggs vary greatly in size, from eight to ten lines in length. Now if it had been of
advantage to this species to have laid eggs even smaller than those now
so as to have deceived certain foster-parents, or, as is more probable, to have been hatched within
shorter period (for it is asserted that there is a relation between
size
and the period of
then there is no difficulty in believing that a race or species might have been formed which would have laid smaller and smaller eggs; for these would have been more safely hatched and reared. Mr. Ramsay remarks that
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