iSSs-] Drew on the Vertical Range of Birth in Colorado. \ *i 



But so evident is it that food supply is the main factor in bird 

 distribution — this regulated by vegetation, and this in turn by 

 climatic influences — that it only needs be said that where food is, 

 there the birds will be found: as. e.g., Creepers and Wood- 

 peckers at 1 1 .000 feet in winter, and Ouzels at the same season 

 feeding in the icy torrents as high as 9000 feet. 



Most birds range high up in summer and lower in fall ; some 

 have a range the reverse of this ; while others early reach their 

 nesting-sites and remain until the time for the complete semi- 

 annual migration comes round. 



Mr. T. M. Trippe, in l Birds of the North-West.' p. 228, has 

 noted the over-migration in spring of Oreoscoptes mo?itan?ts. 

 This trait is common to many, if not all, birds in vertical migra- 

 tion, though I believe not in latitudinal movements. Another 

 peculiarity of vertical migration is the upward range of many 

 birds during the Indian summer days of autumn, e.g., Sturnella 

 neglecta. Scolecoplia^iis cycniocepJialus, Gymnocltta cyano- 

 cephala. This I believe to be the result of a scarcity of food at 

 lower levels, though a somewhat similar reverse migration has 

 been noted at the same season on the New England coast. (See 

 B. N. O. C.,"Oct., 1S80, p. 237, and Coues, B. N. W.. p. 521.) 



The following list, containing the results of five years' work in 

 the State, is believed to be a complete one of the birds found 

 within the boundaries of Colorado. To the south, in New 

 Mexico, climate, and to the north lower average elevation of 

 the mountains, causes considerable variation in the vertical range 

 of birds. But in Colorado, I think, this range is nearly uniform, 

 there being but few birds of the list not of general distribution in 

 the State, and these are chief! v found in the southern portion. 

 Mountain ridges e?i echelon combine to catch many a straggling 

 bird. Several such arc entered on hut a single record, and while 

 showing nothing of distribution, yet may be of interest in future 

 work. Some of those accredited on scanty data are followed by 

 the name of the authority. In the parks are found the only apol- 

 ogies for lakes which the State affords, and around them the 

 few Water Birds which remain during the summer cluster to 

 breed. In many of the upper valleys beaver streams often pro- 

 vide suitable homes for isolated pairs of Ducks, but by far the 

 greater number of our Water Birds are migrants. 



No claim of completeness is made, the notes being offered as 

 a basis on which to engraft other observations, and which, 



