Even The Bats Furnish An Additional Argument, If One Were Needed,
To Show That The Islands Could Not Have Been Peopled From Each
Other And From The Continent Without Some Former Connection.
For
if such had been the mode of stocking them with animals, it is
quite certain that creatures which can fly long distances would
be the first to spread from island to island, and thus produce an
almost perfect uniformity of species over the whole region.
But
no such uniformity exists, and the bats of each island are
almost, if not quite, as distinct as the other mammals. For
example, sixteen species are known in Borneo, and of these ten
are found in Java and five in Sumatra, a proportion about the
same as that of the Rodents, which have no direct means of
migration. We learn from this fact, that the seas which separate
the islands from each other are wide enough to prevent the
passage even of flying animals, and that we must look to the same
causes as having led to the present distribution of both groups.
The only sufficient cause we can imagine is the former connection
of all the islands with the continent, and such a change is in
perfect harmony with what we know of the earth's past history,
and is rendered probable by the remarkable fact that a rise of
only three hundred feet would convert the wide seas that separate
them into an immense winding valley or plain about three hundred
miles wide and twelve hundred long. It may, perhaps, be thought
that birds which possess the power of flight in so pre-eminent a
degree, would not be limited in their range by arms of the sea,
and would thus afford few indications of the former union or
separation of the islands they inhabit. This, however, is not the
case. A very large number of birds appear to be as strictly
limited by watery barriers as are quadrupeds; and as they have
been so much more attentively collected, we have more complete
materials to work upon, and are able to deduce from them still
more definite and satisfactory results. Some groups, however,
such as the aquatic birds, the waders, and the birds of prey, are
great wanderers; other groups are little known except to
ornithologists. I shall therefore refer chiefly to a few of the
best known and most remarkable families of birds as a sample of
the conclusions furnished by the entire class.
The birds of the Indo-Malay region have a close resemblance to
those of India; for though a very large proportion of the species
are quite distinct, there are only about fifteen peculiar genera,
and not a single family group confined to the former district.
If, however, we compare the islands with the Burmese, Siamese,
and Malayan countries, we shall find still less difference, and
shall be convinced that all are closely united by the bond of a
former union. In such well-known families as the woodpeckers,
parrots, trogons, barbets, kingfishers, pigeons, and pheasants,
we find some identical species spreading over all India, and as
far as Java and Borneo, while a very large proportion are common
to Sumatra and the Malay peninsula.
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