132 
Birds of Celebes: Cacatuidae. 
calibre in Cacatua sulphurea (4^ 5) \ in a specimen of that species dissected by 
Garrod “the left only was present, as in C. cristata [— alba), C. leadheateri and 
C. galeritd^ (5), In all other Parrots examined by Garrod the two carotids 
were present; and that author remarks that the genus Cacatua, like the Passer es 
and many others, has lost its right carotid, and in this respect has departed 
most from the ancestral type. 
Judging from the fact that three of the five genera of Cacatuidae recog- 
nised by Count Salvadori are confined to Australia, and that the other two 
(though Microglossus is perhaps rather Papuan than Australian) also occur there, 
and that five of the fifteen species of Cacatua proper are peculiar to Australia and 
the other ten distributed interruptedly between Australia and the Philippines, it is 
evident that unless proof to the contrary is found Australia should be looked upon 
as the chief region of development of the family. Elsewhere no two species of the 
genus Cacatua are known in the same locality. It would appear that, by reason 
of competition, no island is able to harbour more than one species of a section 
of the genus Cacatua-, and the suggestion, that one species has crowded out 
another of another section affords perhaps the most reasonable ground to account 
for their anomalous distribution. 
Gould says that in Australia C. sanguinea and C. galerita are often seen in 
company. This, of course, primarily denotes that their food is the same, and 
that there is plenty of it; if there were not sufficient for both, one species 
would soon become impatient of the other’s company. 
As Krukenberg discovered, the yellow colour of the crest of C. sulphurea 
and of some other Cockatoos is due to the presence of pure psittacofulvin, the 
same pigment, which when laid over a darker ground pigment (fuscin) — not 
present in the Cockatoos, — gives the colour known as parrot-green. The 
yellow pigment was also found by him in the apparently white feathers of 
C. sulphurea, a circumstance which led him to suppose that the young feathers 
are yellow and lose the yellow effect as they become full grown, by reason of 
the distribution of the pigment over a wider area, and of the action of light 
(11)-, but this is not the case as is shown by sprouting feathers in skins before 
us. Light, however, certainly exercises a blanching effect upon them. The 
nestling of other species is clothed in long white down, as Finsch states; 
that of C. sulphurea is unknown. Prof. Marshall expresses the opinion that the 
delicate red and yellow tones of the plumage of Cockatoos is due to the fine 
epithelial dust cast off by the powder-down feathers — which are highly deve- 
loped in Parrots — acting like a powdery pigment on the contour feathers (14). 
But this is not the case in C. sulphurea, where the powder-down feathers are 
white and the dust cast off of the same colour. The white Pigeons of the 
genus Myristicivora are saturated with a similar yellow, which soon fades after 
death on exposure to the light, leaving the birds white. Such is also the case 
with the salmon-colour with which the white breast of the Moleo is tinted. ^ 
