6 RUDOLF SÖDERBERG, STUDIES OF THE BIRDS IN NORTH WEST AUSTRALIA. 
studies in the bird-life of the country. The journey was continued by sea to Derby 
(g' on the map) in North West Australia, from where we started our trip inland on 
the 26th of October 1910. 
The plan of the expedition was to follow the caravan-route along the Fitzroy 
river. Thanks to the information I got from Mr. Y. RoGERS, who had made large 
collections here, and from Mr. CROSSMAN, who had also studied the bird-fauna of 
the country round Broome, I was enabled to form the plan LAURELL and I later 
followed. Our interests made it necessary to look out for absolutely virgin regions, 
where the best results were to be expected. At a cattle-station, called Lower Leverynga, 
about 70 miles from Derby, we separated from the expedition and pushed rapidly 
southwards, with saddle and pack horses, along the now dried up Jurgarry creek, 
Close to the mountains of the desert, at a point, called by a bushman, whom we 
met here, Mowla Downs, we stopped. We arrived there on the 8th of November 
(3? on the map). 
The nature formed a transition between the region of the desert mountain and 
the Kimberley region. A description of the conditions prevailing there will be found 
in the next chapter. Here I shall only mention, that, with regard to the breeding 
of the birds, the nature and climate of the country, and the features of the animal- 
life before and after the rain-period, this very fatiguing journey gave the most ample 
results. ROGERS, who has mentioned in a letter, that he visited the same place later 
on, though only for a short time, because of »the hard conditions», also made very 
good ornithological observations there. No doubt this region was, as my authorities 
had presumed, regarding as well the changes of the West Australian nature as the 
birds and their wanderings, more characteristic than any other place on the main- 
land that the expedition visited. I will also point out Mowla Downs as the place, 
where we met with real wild natives. 
It is here suitabie to remark that, in consequence of the mobility, to which 
the bird-fauna in North West Australia is exposed — a subject, which may be men- 
tioned later — the composition of species may be different in places situated relatively 
near to each other, while — perhaps in consequence of accidental circumstances — 
it corresponds better in two rather widely separated places. This discontinuity in 
the extension of the several species is caused by the lack of water and the similarity 
of the natural features, for most of the common species must lead a wandering life 
during by far the greater part of the year. 
Certainly we came across some species of a more local extension, but on the 
whole the various species had a vast extension. At Mowla Downs it was particularly 
the existence of the desert-mountains which conditioned the presence of the former, 
accommodated to the nature of the mountain. Such a form as Petrochelidon nigricans 
neglecta, here very common, was for instance seen at the coast and in other places, 
while Lophophaps ferruginea was local and spread over the desert-mountains. Similar 
observations were made in other places. Of the different occurrences of the various 
species in different places an exact account will be given in the systematic part. 
