BALD PEAKS AND GREEN VALES 63 



The winter haunts of Audubon's warblers are farther 

 south than Colorado, mostly in Mexico and Guatemala, 

 although a few of them remain in the sheltered moun- 

 tain valleys of the western part of the United States. 

 Early in May they appear on the plains of eastern Col- 

 orado, where they are known only as migrants. Here a 

 double movement presently takes place what might 

 be called a longitudinal and a vertical migration one 

 division of the warbler army sweeping north to their 

 breeding grounds in Canada, and the other wheeling 

 westward and ascending to the alpine heights among 

 the mountains, where they find the subartic conditions 

 that are congenial to their natures without travelling so 

 great a distance. Here they build their nests in the 

 pine or spruce trees, rear their families, and as autumn 

 approaches, descend to the plains, tarry there a week or 

 two, then hie to their winter homes in the South. 



One of the most gorgeous tenants of this valley was 

 Wilson's warbler. 1 It wears a dainty little cap that is 

 jet black, bordered in front and below with golden yel- 

 low, while the upper parts are rich olive and the lower 

 parts bright yellow. These warblers were quite abun- 

 dant, and were evidently partial to the thickets covering 

 the boggy portions of the vale. While Audubon's 



1 Mr. Aiken says, " The Rocky Mountain representative of 

 Wilson's warbler is an intermediate form, nearest the Pacific coast 

 bird which is distinguished as the pileolated warbler." 



