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 many 

 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 lyowe 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 lyoveland; 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 thoroi^h knowledge of 

 the main features of the ornithology of this^fegion. About a 

 dozen other ornithologists have given us results of short visits 

 to various places i^ this belt. 



