18 RUDOLF SÖDERBERG, STUDIES OF THE BIRDS IN NORTH WEST AUSTRALIA. 
appeared in small flocks, and Ephthianura tricolor assimilis, which was common every- 
where, Ånthus australis, found scattered, Java finches in flocks, Merops ornatus, the 
kites as well, and also Hieracidea occidentalis, which approached the abodes of man 
in great numbers. 
In fact this nomadic life largely characterizes the bird-world during the greater 
part of the year, since even the summer months are in some measure remarkable for 
it. Within its area of distribution a species seems, then, to stray about in search of 
food and only remains in the same place long in the breeding season. 
I also got the decided impression that though the rainy season caused most 
noticeable movement in the bird-fauna, so that birds arrived in flocks and spread 
over the country, many representatives of the fauna would not try to find or return 
to their birth-places, but settled down in the neighbourhood of or in the very place, 
where they lived for the moment. The extraordinary uniformity of the bush makes 
it impossible for a bird species to re-discover its former breeding-place, quite contrary 
to what the case generally is in the North. 
It is clear that also because of that fact the bird-fauna of a place must be 
recruited (or on the contrary) by different bird-forms in different seasons, which 
explains the conspicuous discontinuous distribution of many birds. 
Finally it must be indicated that the uniformity of the nature has evidently 
caused not only peculiar conformity as to wanderings and distribution in much dif- 
ferent birds, but also conformity in conditions of life, which one traces in many 
different species. 
Means of getting food, habits of nest-building, movements, tones ete. are in 
several respects more equable in different groups of the birds of West Australia than 
one would think. 
The birds? feathers — morphological phenomena and the conditions under which they moult. 
Investigations of the moulting of the birds and their changes of appearance 
are important first because they furnish us with knowledge of the birds” dependence 
on the climate and the changes of seasons, and secondly because they show the 
alterations which the sexual characters of the dress as the feathers themselves undergo 
in relation to that of the adult bird. 
In regard to the last consideration the question of the genetic connection which 
the appearance of the young birds may have in corresponding appearances of other 
species of the same kind or other races gives such investigations their greatest value. 
It might also be added, that the moulting may indirectly give important information 
about the life of the bird, in this case closely connected with propagation. 
Such investigations, however, have seldom been carried out on the material, 
that had been brought together by expeditions. My aim was therefore to give to 
the matter as much time and interest as the circumstances would permit. The ob- 
servations thus made are given under the respective species. Concerning some cases 
particularly detailed accounts of the matter are given. In these cases there was no 
