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 oenanthe was taken near Boulder, a Bendire’s 
Thrasher at Colorado Springs, an Olivaceous Flycatcher at Fort 
Lyon, 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 temperature 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. 
