﻿stejneger] birds of genus cinclus 4 2 5 



Without paleontologic evidence it would be impossible to saj 



with any degree of approximation when this radiation took place, 

 and there is bul slim chance that we shall ever have such evidence. 

 However, the indications arc that so deep-seated modifications as 

 we have seen that the dippers have undergone, as well as others to 

 be mentioned later on, must have required a comparatively I 

 time for their accomplishment. If I were to make a guess, I should 

 place the origin and beginning of the dispersal of the dippers not 

 later than the dawn of the Tertiary. 



Geologists and bio-geographers seem pretty well agreed that at 

 that time the eastern portion of Asia and Xorth America were con- 

 nected by a land bridge somewhere about Bering Sea, and that a 

 great uplift took place which was the beginning of the mountain 

 ranges which from Alaska southward parallel our Pacific coast. In 

 eastern Asia similar ranges stretch out from the elevated region 

 alluded to above northeastward towards Bering Sea. Along this 

 route it would not have been difficult for the ancestor of our Cinclus 

 unicolor to have found his way into western Xorth America. 



Before proceeding further it may be well to remark that the 

 ancestral dipper must have been in every respect, both as to structure 

 and to habits, a typical Cinclus. Before he left the original home 

 he must have acquired all the peculiarities so characteristic of the 

 genus, since in all these details the most remotely located members of 

 the group are essentially a unit. The species rearing its young on 

 the confines of Patagonia in nearly all particulars, except color, 

 conforms with the one " dipping " on the snow-fells of far away 

 Scandinavia. 



All these structural peculiarities and the habits of the bird are 

 strictly interrelated. In other words, as the ancestral dipper had the 

 essential structure of the dippers of to-day. so he also had their 

 habits, and as these again interact with the conditions of life and 

 surroundings, so the ancestral dipper must have inhabited the same 

 life-zone as its descendants. From the latter we are therefore justi- 

 fied in concluding backwards as to the conditions under which the 

 ancestor lived. As the dipper lives to-day so he lived in Miocene 

 times. 



It cannot be the purpose in this connection to give an extendea 

 account of the interesting habits of these birds, but sufficient should 

 be said to fully explain the conditions necessary to enable the dippers 

 to emigrate into distant lands. 



The dipper breeds in the upper portion of the boreal zone, extend- 

 ing upwards or northwards into the arctic-alpine zone, in closest 

 proximity to cold rushing mountain streams. These he follows some 



