BIRDS OF BOULDER COUNTY, COLORADO 1 



By Norman deWitt Betts* 



Introduction and Acknowledgments 

 Geography of Boulder County 

 Annotated List 

 Vertical Distribution 

 Local Migration Problems 

 Bibliography (by Junius Henderson) 



Introduction and Acknowledgments 



The bird-life of Colorado has received considerable attention dur- 

 ing the past few years. The state is a large one, however, and with 

 the varied conditions belonging to a mountainous region, with semi- 

 arid plains and alpine summits, its bird problems are not soon 

 exhausted. The large variations in altitude mean that questions of 

 zonal distribution and of local migration from plains to mountains 

 are added to the work called for in the study of a "one-climate" 

 locality. Conclusive data on vertical migration can be obtained only 

 through the co-operation of several observers. The mountainous 

 region, furthermore, renders difficult the careful and systematic 

 observations necessary to a knowledge of the distribution of the 

 breeding birds in relation to altitude. It is an extensive area with a 

 need for intensive work, a work for which a locality, or county, list 

 seems better adapted than a state list. Boulder County embraces 

 areas quite typical of the northeastern quarter of the state and seems 

 well situated for systematic study. 



1 Publication of the Colorado Biological Survey, No. 15. Other articles published recently (all in these 

 Studies) are: No. o, "Animals and Plants described as new from Colorado in ion," by T. D. A. Cockerell; 

 No. 10, "The Sawflies of Boulder County, Colorado," by Sievert A. Rohwer; No. n, "Preliminary List of the 

 Algae of Colorado," by Wilfred W. Robbins; No. 12, " Some Desmids from Alpine Stations in Colorado," by 

 G. H. Wailes; No. 13, "The Grass Flora of Tolland, Colorado , and Vicinity," by Francis Ramaley and Miss 

 Mary Esther Elder; No. 14, "The Amphibia and Reptilia of Colorado," Part I, by Max M. Ellis and Junius 

 Henderson. 



* The field studies by Mr. Betts were made while he was engineer of the timber-testing station at the 

 University of Colorado. This article was prepared at the editor's request. — Editor. 



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SEP 2 3 1935 



