62 RUDOLF SÖDERBERG, STUDIES OF THE BIRDS IN NORTH WEST AUSTRALIA. 
specimens, shot in May at Meda, do not show any moulting. Thus the moulting-season 
is in Jan. and Febr. Thus it corresponds to the most violent outbreak of the rainy 
season, and the hottest period of the summer, and comes immediately after the dry 
and sterile season. The breeding takes place at the same time or directly after or 
a little later than the moulting-season. 
The plumage of the three males taken in May is perfect (except the small 
wingcoverts) and rather pretty, their principal moulting, evidently like that of the 
females, having taken place in Jan. and Febr. But one specimen from Nooncanbah 
of the l7th of Jan. has not only a plumage in which the moulting has arrived at 
its last stage or perhaps is already completed (the feathers of the neck and ear 
are all new etc.), but has even begun dropping the small wing-coverts. Otherwise 
these are the last to be dropped and replaced, and in all the other moulting spe- 
cimens they have not yet been moulted. A male taken the same day as the above- 
mentioned female (Jan. 17th) shows, however, a rather typical case of moulting. 
Another specimen, a female taken in July (Beagle bay), is almost complete in the 
other parts of the body, but on the back and among the tail-feathers the change is 
going on. One of the tail-feathers shows the peculiar abrasion phenomenon. 
Juvenal J. — Is quite like the female. Shot '"/s 1911 (Meda). The moult 
quite complete on back, belly and head, but is going on in the small wing-coverts. 
In this bird there is a partial discolouring of the feathers as in many of the other 
specimens. Thus there are still blue and glossy surfaces in those parts of the pri- 
maries and secondaries etc. that have lain hidden under the covering feathers. It 
is an external effect caused by the burning sun. 
This young male, which still has the female plumage, can hardly have been 
born this year but probably late in the summer (March) the year before. 
What has now been said about bleaching-phenomena explains why in May some 
birds look as if they were moulting. Some feathers, which have lain hidden, have 
come up to the surface and show a fresh blue colour, while those, that have been 
the uppermost ones before, look as if they were old. In this way a discolouring 
of the plumage may take place rather quickly. It has, of course, nothing to do 
with the moulting, but may be misleading in dry, preserved specimens. 
Ecological. — In all the places that the Expedition visited this stately bird 
was observed. At Sunday Island, however, it did not appear, but from Mr. S. 
HapLEY I heard that now and then it comes to visit the mainland from the con- 
tinent. No other cockatoo except this one and Licmetis pastinator have been seen 
there. At Mowla Downs it was observed, but there it was not seen in great numbers. 
It can hardly be said to be really common, for the flocks are in all places very 
solitary and scattered. The biggest flocks I saw in Beagle bay and Meda consisted 
of 15—20 birds, but for the most part it appeared in very much smaller numbers, 
6—8 together. At Meda it used to pass certain places at fixed hours, having its 
high-way there, especially at sunset. Their flight is lazy and slow with heavy strokes 
of the wing and its characteristic scream is often heard, which is distinguished from 
that of other cockatoos by its protracted and melancholy tone. It was not shy. It 
