CriAP. XVI. THE YOUNG LIKE BOTH ADULTS. 209 



acquired through sexual selection by the nearly mature 

 males ; but that, differently from what occurs in the 

 two first classes, the transmission, though limited to the 

 same age, has not been limited to the same sex. Conse- 

 quently both sexes when mature resemble each other 

 and differ from the young. 



Class IV. Wlien the adult male resembles the adult 

 female, the young of both sexes in their first plumage 

 resemble the adults. — In this class the young and the 

 adults of both sexes, whether brilliantly or obscurely 

 coloured, resemble each other. Such cases are, I think, 

 more common than those in the last class. We have 

 in England instances in the kingfisher, some wood- 

 peckers, the jay, magpie, crow, and many small dull- 

 coloured birds, such as the hedge- warbler or kitty- wren. 

 But the similarity in plumage between the young and 

 the old is never absolutely complete, and graduates away^ 

 into dissimilarity. Thus the young of some members of 

 the kingfisher family are not only less vividly coloured 

 than the adults, but many of the feathers on the lower 

 surface are edged with brown,^^ — a vestige probably of 

 a former state of the plumage. Frequently in the same 

 group of birds, even within the same genus, for instance 

 in an iVustralian genus of parrokeets (Platycercus), the 

 young of some species closely resemble, whilst the 

 young of other species differ considerably from their 

 parents of both sexes, Avhich are alike.^^ Both sexes 

 and the young of the common jay are closely similar ; 

 but in the Canada jay (Perisoreus canadensis) the young 

 differ so much from their parents that they were formerly 

 described as distinct species."^ 



2r Jerdon, ' Birds of India,' vol. i. p. 222, 228. Gould's ' Htiudbook 

 of the Birds of Australia,' vol. i. 124, 130. 



28 Gould, Ibid. vol. ii. p. 37, 4G, 56. 



29 Audubon, ' Ornith. Biography,' vol. ii. p. 55. 



VOL. II. P 



