Chap. XV. COLOUR AND NIDIFICATION. 175 



« 



plain, it occurred to me that this colour might possibly 

 make the female dangerously conspicuous, whenever 

 she put her head out of the hole containing her nest, 

 and consequently that this colour, in accordance with 

 Mr. Wallace's belief, had been eliminated. This view is 

 strengthened by what Malherbe states with respect to 

 Lidopieus carlotta ; namely, that the young females, 

 like the young males, have some crimson about their 

 heads, but that this colour disappears in the adult 

 female, whilst it is intensified in the adult male. Never- 

 theless the following considerations render this view 

 extremely doubtful: the male takes a fair share in 

 incubation,^^ and would be thus far almost equally 

 exposed to danger ; both sexes of many species have 

 their heads of an equally bright crimson ; in other 

 species the difference between the sexes in the amount 

 of scarlet is so slight that it can hardly make any 

 appreciable difference in the danger incurred ; and 

 lastly, the colouring of the head in the two sexes 

 often differs slightly in other ways. 



The cases, as yet given, of slight and graduated 

 differences in colour between the males and females 

 in the groups, in which as a general rule the sexes 

 resemble each other, all relate to species which build 

 domed or concealed nests. But similar gradations may 

 likewise be observed in groups in which the sexes 

 as a general rule resemble each other, but which build 

 open nests. As I have before instanced the Australian 

 parrots, so I may here instance, without giving any 

 details, the Australian pigeons.^^ It deserves especial 

 notice that in all these cases the slight differences in 



25 Audubon's ' Ornithological Biography,' vol. ii. p. 75 j see also the 

 ' Ibis,' vol. i. p. 268. 



i^6 Gould's ' Handbook of the Birds of Australia,' vol. ii. p. 109-149. 



