178 UNIVERSITY OF COLORADO STUDIES 



In 1909 Professor Junius Henderson published a list 1 of the birds 

 of Boulder County. The present paper is a revision of that list 

 together with a brief analysis of the bird-life of the region. While a 

 few species have been added to the 1909 list, the chief aim in the 

 revision has been to bring together the information bearing on rela- 

 tive abundance, zonal distribution, and dates of migration and nesting 

 of the birds occurring regularly in the county. Information con- 

 cerning the migrant water-birds is very incomplete in regard to the 

 species occurring, as well as to their abundance and time of migration. 

 Quite full information has, however, been published concerning the 

 water-birds of the Barr chain of lakes, about fifteen miles east of the 

 county line. This has been used as a guide to the probable status of 

 several species in the county. 



The information as to nesting has been secured chiefly from the 

 notes and collections of eggs made by Denis Gale 2 during the years 

 1883 to 1893, and now in the University of Colorado Museum. 

 Migration dates are largely from the field notes of Professor Henderson 

 and the writer. The estimates of relative abundance and distribution 

 have been based to a large extent on the writer's notes, made during 

 a three years' residence in the county, though free use was made of such 

 information in Gale's notes and in Henderson's list as was definite in 

 regard to the altitudinal zones adopted. For a number of migration 

 dates not acknowledged in the text, the writer is indebted to Dr. S. 

 Griswold Morley and to Mr. Dean Babcock. For information con- 

 cerning the adjacent districts — Estes Park, Loveland and the Barr 

 Lakes — the available literature 3 has been consulted and many refer- 

 ences thereto incorporated in the annotated list. 



1 Henderson, Junius, "Annotated List of the Birds of Boulder County, Colorado," University of Colo- 

 rado Studies, Vol. VI, No. 3, April, 1909. (This list includes a full bibliography of papers published up to 1909.) 



> See Auk, Vol. XXII, October, 1905. 



' Sclater, W. L., A History of the Birds of Colorado, 1912. 



Cooke, W. W., Birds of Colorado, Colorado State Agric. Col., 1897-1900. 



Felger, A. H., "Annotated List of the Water Birds of Weld, Morgan and Adams Counties, Colorado," 

 Auk, 1909. 



Hersey and Rockwell, "Annotated List of the Birds of Barr Lake District, Adams County, Colo- 

 rado," Condor, 1909. 



Kellogg, V. L., "Summer Birds of Estes Park, Colorado," Trans. Kans. Acad. Sci., 1889. 



Wddmann, Otto, "List of Birds Observed in Estes Park, Colorado," Auk, 1911. 



