4 BIRDS OF COLORADO. 



in the middle west. As additions to these, there come to the 

 State from the east such distinctively eastern species as the 

 Bobolink, Phoebe, Blue Bird, and Baltimore Oriole; from the 

 west the Dwarf Hermit Thrush, Grace's Warbler, Golden- 

 crowned Sparrow, and the Black Swift; from the north 

 Holboell's Grebe, Arctic Tern, Harlequin Duck, and Barrow's 

 Golden-eye; while something over twenty truly southern species 

 have been taken as stragglers in southern Colorado. 



Of accidental visitants we have our share. Three varieties 

 of Surf Ducks have wandered to Colorado; a specimen of the 

 English Saxicola cenantke was taken near Boulder, a Bendire's 

 Thrasher at Colorado Springs, an Olivaceous Flycatcher at Fort 

 Ivyon, a White-winged Dove in Jefferson County, a White Ibis 

 at Denver, a Roseate Spoonbill at Silverton, and most wonder- 

 ful of all, a Scarlet Ibis near Pueblo. 



The broken character of the surface of Colorado offers in- 

 ducements for birds of all kinds. The eastern third of the 

 State is a vast plain, rising from an altitude of 3,500 feet at its 

 eastern edge to nearly 6,000 feet where it joins the foothills of 

 the Rockies. This whole region is treeless, except a narrow 

 fringe along the streams. Innumerable throngs of birds sweep 

 across it during migration, especially water fowl and waders, 

 but its attractions are too few to induce many to remain through 

 the summer. 



The center of the State is occupied by the Continental 

 Divide. Range on range attaining a height of over 14,000 feet 

 offers favorable conditions for even boreal species. The great 

 mountain parks lie in this section, and at an altitude of 8,000 

 feet mark the limit of height reached by the great bulk of the 

 species. 



The western third of Colorado presents a wilderness of 

 rolling hills from 5,000 to 8,000 feet in altitude, covered with a 

 few trees and a very scanty vegetation. Bird life is present in 

 small numbers but great variety and partakes largely of west- 

 ern characteristics. 



The temperature of Colorado is much below that of cor- 

 responding latitudes in the Mississippi Valley. On the plains 

 the average for the year is not far from 52° F., with extremes 

 more marked and changes more sudden than in moister cli- 

 mates. At 7,000 feet among the mountains the average tem- 

 perature is five degrees lower, and at 9,000 feet only a little 

 colder. 



Timber line is about 11,500 feet in Colorado and with an 

 average temperdlSre of two degrees below freezing is yet the 

 home of some birds for the entire year, while during the short 

 summer many species find here congenial nesting sites. 



