﻿STEJNEGER] birds of genus cinclus 427 



The geologists tell us that during the lower Tertiary a wide sea 

 rolled across what is now the isthmus of Panama. Until the land 

 rose and joined the two continents the dipper could not pass into 

 South America. However, the connection was made early enough 

 for our purpose* and the dipper had probably gained a foothold in 

 the Andes before the advent of the Pliocene. 



The specialization begun in North America continued under the 

 southern sky. The large while patch on the underside of the wing 

 is a common birthmark of all the South American species of dippers 

 and proves them all to have descended from a single stock which 

 acquired this character probably shortly after the arrival in South 

 America. Other differentiations in plumage took place aided by 

 more perfect isolation of the various colonies on the boreal islands 

 of an otherwise tropical mountain system than could take place in 

 more northern latitudes. The dipper which reached farthest south 

 {Cinclus schuhi) seems to have become most modified, for it has 

 acquired a light rufous throat, a character entirely unique in the 

 genus. 



Let us now return to the supposed original home of the dippers 

 in the Chinese mountain. As already stated (p. 424) we have two 

 separate types there, one uniformly fuscous, the other pied, white 

 and dusky. The uniform dark style seems to be the older which 

 preoccupied the mountains of the old land mass to the northeast and 

 east extending as far as Formosa, Japan, and the Stanovoi moun- 

 tains 1 for an unknown distance. Local influences in connection with 

 more or less imperfect isolation have carved out a number of races 

 such as C. asiaticus in the Himalayas, C. pallasii in eastern Siberia, 

 Japan, etc., C. marila in Formosa, C. siemsseni in the province of 

 Fokien, China, C. souliei in Tibet, C. bilkcvitchi, in the Altai Moun- 

 tains, etc., etc., but with a more or less uniformly colored bird to 

 work upon the' variation could not be so very great, and some of 

 these races must be very difficult to distinguish. 



The pied style, as exemplified by the common European dipper, 

 probably came into being somewhat later when the western mountain 

 ranges rose up out of the Miocene Sea. According to the rules of 

 zoological nomenclature, which now govern our scientific termi- 

 nology, the name Cinclus cinclus (Linnaeus) is that of the " species " 

 and those forms which have been described later are " sub-species," 

 as for instance, C. cinclus cashmeriensis. But it is more likely that 



1 By this name is meant the various mountain systems extending in a north- 

 easterly direction from the great bend of the Amur river and forming the 

 watershed between the Arctic and the Pacific Oceans. 



