. . . . . . 36 Australian birds . . . 13
Closely allied species . . 11 Closely allied species . . 35
Derived from Java . . . . 47 Derived from Australia . . . 48
We have here a wonderful agreement in the number of birds belonging to
Australian and Javanese groups, but they are divided in exactly a
reverse manner, three-fourths of the Javan birds being identical
species and one-fourth representatives, while only one-fourth of the
Australian forms are identical and three-fourths representatives. This
is the most important fact which we can elicit from a study of the
birds of these islands, since it gives us a very complete clue to much
of their past history.
Change of species is a slow process - on that we are all agreed, though
we may differ about how it has taken place. The fact that the
Australian species in these islands have mostly changed, while the
Javan species have almost all remained unchanged, would therefore
indicate that the district was first peopled from Australia. But, for
this to have been the case, the physical conditions must have been
very different from what they are now. Nearly three hundred miles of
open sea now separate Australia from Timor, which island is connected
with Java by a chain of broken land divided by straits which are
nowhere more than about twenty miles wide. Evidently there are now
great facilities for the natural productions of Java to spread over
and occupy the whole of these islands, while those of Australia would
find very great difficulty in getting across. To account for the
present state of things, we should naturally suppose that Australia
was once much more closely connected with Timor than it is at present;
and that this was the case is rendered highly probable by the fact of
a submarine bank extending along all the north and west coast of
Australia, and at one place approaching within twenty miles of the
coast of Timor. This indicates a recent subsidence of North Australia,
which probably once extended as far as the edge of this bank, between
which and Timor there is an unfathomed depth of ocean.
I do not think that Timor was ever actually connected with Australia,
because such a large number of very abundant and characteristic groups
of Australian birds are quite absent, and not a single Australian
mammal has entered Timor - which would certainly not have been the case
had the lands been actually united. Such groups as the bower birds
(Ptilonorhynchus), the black and red cockatoos (Calyptorhynchus), the
blue wrens (Malurus), the crowshrikes (Cracticus), the Australian
shrikes (Falcunculus and Colluricincla), and many others, which abound
all over Australia, would certainly have spread into Timor if it had
been united to that country, or even if for any long time it had
approached nearer to it than twenty miles. Neither do any of the most
characteristic groups of Australian insects occur in Timor; so that
everything combines to indicate that a strait of the sea has always
separated it from Australia, but that at one period this strait was
reduced to a width of about twenty miles.
Enter page number
PreviousNext
Page 149 of 219
Words from 77384 to 77905
of 114260
