12 Drew on the Vertical Range of Birds in Colorado. [January 



the mean annual precipitation will not exceed 20 inches, — 

 being 12 to 14 inches on the plains, and increasing to 32 inches 

 in the mountains. 



As is well known, the flora of the plains is strongly character- 

 ized by buffalo grass, sun flowers, and cacti, and as a natural result, 

 Fringillida? and Raptores predominate there over all other forms 

 of bird life. 



Entering the foothills, which reach an average elevation of 

 8000 feet, the pinon {Finns edulis) and dwarf oak (Querczts 

 alba gunnisoni) at once become abundant, and their matted 

 clumps and tangled underbrush make hiding places for many 

 Warblers. On the shoulders of the foothills rest the mountain 

 parks, with a mean elevation of Sooo feet. They are treeless and 

 plain-like, being covered with grass and sage, save where the 

 grass has been killed out by grazing herds ; then the shifting 

 sands prevent aught but sage from maintaining a foothold. 



The bases of the main peaks have an elevation of about 

 8000 feet ; thence they rise rapidly, drawing themselves aloof 

 from the life of the plains. And, indeed, it is only those 

 birds which pass up into these uppermost levels which can 

 properly be called mountain inhabitants, the great parks thus 

 forming the real dividing ground between the summer camps of 

 the hardier lowland birds and the homes of those to the manor 

 .born. Nor do the straggling migrants but rarely wander over 

 the mountains themselves, but, instead, into these parks. 



The latitudinal range of birds in the United States has been 

 quite fully worked out, and notes on the close connection between 

 vertical and geographical distribution are not few ; yet, so far as 

 I know, no one has tabulated the vertical range. References to 

 elevations at which birds have been found in summer are quite 

 frequent. Especially is this the case in Allen's w Ornithological 

 Reconnoissance in Kansas,' etc., and Ridgway's 'Ornithology of 

 the 40th Parallel,' and many are given by Mr. T. M. Trippe in 

 Coues's 'Birds of the Northwest.' I have freely borrowed from 

 these sources, as well as from Henshaw's ' Report' on birds in 

 volume V of Wheeler's Surveys, and from Ridgway's paper on 

 Colorado Birds in 'Bull. Essex Inst.', Vol. V, No. 11. 



One working in different parts of the State will soon perceive 

 the floral limits to be quite sharply defined. To a certain, though 

 less extent, the birds also are shut in by almost intangible barriers. 



