BIRDS OF COLORADO. 
5 
The rainfall on the plains is about fourteen inches per 
year, increasing to twenty inches at 8,000 feet in northern Colo- 
rado, but in the southern scarcely reaching that amount until 
nearly to timber line. This scarcity of rain has a direct influ- 
ence on the vegetation and through that on the distribution of 
the birds. With the exception of a few species of sparrows, 
almost all the bird life of the State is confined to the vicinity 
of water or high enough on the mountains to reach timber. 
The records given in this bulletin are based first of all on 
the printed matter that has appeared dealing with the birds of 
Colorado. This mass of material has been supplemented by 
much manuscript matter, and by the personal observations of 
the author during a four years’ residence in the State. 
There is no State in the Union that offers a more difficult 
field for thorough work, and a recapitulation of our present 
knowledge only serves to bring out more clearly the mauy 
points on which further information is needed. 
The only claim for completeness made by the present list 
is that it is complete so far as work done up to this time is con- 
cerned. Experience in this State as well as in others teaches 
that additions will be made for many years to come. These 
will not be confined to any one part of the State nor to any par- 
ticular class of birds. In addition to accidental visitants, it 
may be confidently expected that several more eastern species 
will be found to follow up the Arkansas and the Platte Rivers, 
and a still greater number of western species up the valley 
of the Grand into western Colorado. 
Though much ornithological work has been done in Colo- 
rado, many parts of the State have never yet been visited by 
an ornithologist. The region along the eastern base of the 
foothills at the juncture of mountain and plain has been quite 
thoroughly studied. Fully four-fifths of all the records of Colo- 
rado pertain to this narrow strip, thirty miles wide and one 
hundred and fifty miles in length. As this constitutes less than 
one-twentieth of the area of the State, it can be seen how little 
attention has been paid to much of Colorado. In this strip, 
Beckham, Nash and Lowe have worked at Pueblo; Aiken at 
Pueblo, Canon City and Colorado Springs; Allen at Colorado 
Springs; Henshaw, Anthony and H. G. Smith at Denver; 
Trippe at Idaho Springs; Gale at Gold Hill ; W. G. Smith and 
Osburn at Loveland; Breninger at Fort Collins, and Dille at 
Greeley. In most cases this work has been continuous through 
the year, and has resulted in a pretty thorough knowledge of 
the main features of the ornithology of this region. About a 
dozen other ornithologists have given us results of short visits 
to various places in this belt. 
