618 THE DESCENT OF MAN 



the female is more conspicuously colored than the male, 

 although nothing is known about the manner of incuba- 

 tion. With the carrion-hawk of the Falkland Islands 

 (Milvago leucurus) I was much surprised to find by dis- 

 section that the individuals which had all their tints 

 strongly pronounced, with the cere and legs orange col- 

 ored, were the adult females, while those with duller 

 plumage and gray legs were the males or the young. In 

 an Australian tree-creeper {^Glimacteris erythrops) the fe- 

 male .differs from the male in "being adorned with beau- 

 tiful, radiated, rufous markings on the throat, the male 

 having this part quite plain." Lastly, in an Australian 

 night- jar, "the female always exceeds the male in size 

 and in the brilliance of her tints; the males, on the other 

 hand, have two white spots on the primaries more conspic- 

 uous than in the female."" 



We thus see that the cases in which the female birds are 

 more conspicuously colored than the males, with the young 

 in their immature plumage resembling the adult males in- 

 stead of the adult females, as in the previous class, are not 

 numerous, though they are distributed in various Orders. 

 The amount of difference, also, between the sexes is incom- 

 parably less than that which frequently occurs in the last 

 class; so that the cause of the difference, whatever it may 

 have been, has here acted on the females either less ener- 



^^ For the Milvago, see "Zoology of the Voyage of the Beagle": Birds, 

 1841, p. 16. For the Climacteris and night-jar (Euros topodos), see Gould's 

 "Handbook to the Birds of Australia," vol. i. pp. 602 and 97. The New Zea- 

 land shieldrake (Tadorna variegata) offers a quite anomalous case; the head 

 of tlie female is pure white, and her back is redder than that of the male ; the 

 head of the male is of a rich dark bronzed color, and his back is clothed with 

 finely pencilled slate-colored feathers, so that altogether he may be considered 

 as the more beautiful of the two. He is larger and more pugnacious than the 

 female, and does not sit on the eggs. So thai in all these respects this species 

 comes under our first class of cases; but Mr. Sclater ("Proc. Zool. Soc," 1866, 

 p. 150) was much surprised to observe that the young of both sexes, whea 

 about three months old, resembled in their dark heads and necks the adult 

 males, instead of the adult females ; so that it would appear in this case that 

 the females have been modified, while the males and the young have retained 

 a former state of plumage. 



