Travel Reference
In-Depth Information
We now see that the total number of birds which seem to have been derived from Java
and Australia is very nearly equal, but there is this remarkable difference between the two
series: that whereas the larger proportion by far of the Java set are identical with those still
inhabiting that country, an almost equally large proportion of the Australian set are distinct,
though often very closely allied species. It is to be observed also, that these representative or
allied species diminish in number as they recede from Australia, while they increase in num-
ber as they recede from Java. There are two reasons for this, one being that the islands de-
crease rapidly in size from Timor to Lombock, and can therefore support a decreasing num-
ber of species; the other and the more important is, that the distance of Australia from Timor
cuts off the supply of fresh immigrants, and has thus allowed variation to have full play;
while the vicinity of Lombock to Bali and Java has allowed a continual influx of fresh indi-
viduals which, by crossing with the earlier immigrants, has checked variation.
To simplify our view of the derivative origin of the birds of these islands let us treat them
as a whole, and thus perhaps render more intelligible their respective relations to Java and
Australia.
The Timor group of islands contains:—
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 there-
fore 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 connec-
ted with Java by a chain of broken land divided by straits which are nowhere more than
