Chap. XV.] COLOR AND NIDIFICATION. 167 



male. As in several woodpeckers the head of the male is 

 bright crimson, while that of the female is plain, it oc- 

 curred to me that this color might possibly make the 

 female dangerously conspicuous, whenever she put her 

 head out of the hole containing her nest, and consequent- 

 ly that this color, in accordance with Mr. Wallace's belief, 

 had been eliminated. This view is strengthened by what 

 Malherbe states with respect to Indopicus carlotta ; 

 namely, that the young females, like the young males, 

 have some crimson about their heads, but that this color 

 disappears in the adult female, while it is intensified in 

 the adult male. Nevertheless, the following considera- 

 tions render this view extremely doubtful : the male takes 

 a fiiir 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 difierence between the sexes in the amount of 

 scarlet is so slight that it can hardly make any appre- 

 ciable difference in the danger incurred ; and, lastly, the 

 coloring of the head in the two sexes often differs slightly 

 in other ways. 



The cases, as yet given, of slight and graduated differ- 

 ences in color 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 

 deseiwes especial notice that in all these cases the slight 

 differences in plumage between the sexes are of the same 



^^ Audubon's ' Ornithological Biography,' vol. ii. p. '75 ; see also the 

 'Ibis,' vol. I p. 268. 



^^ Gould's 'Hand-book of the Birds of Australia,' vol. ii. pp. 109-149. 



