THE 



WILSON BULLETIN 



NO. 57. 



A QUARTERLY JOURNAL OF ORNITHOLOGY 



VOL. XVIII DECEMBER, 1906 NO. 4 



WITH THE BIRDS IN NORTHEASTERN 

 COLORADO. 



BY JUNIUS HENDERSON. 



On June T, 190G, the writer with three assistants started 

 northeastward from Boulder, for a month's geological and bio- 

 logical expedition to the Chalk Blufifs and Pawnee Buttes re- 

 gion in northern Weld County, in the interests of the Uni- 

 versity of Colorado. It being the nesting season and the ma- 

 jority of the nests containing young birds, we did but little 

 bird collecting, but contented ourselves, so far as our feathered 

 neighbors were concerned, with photographing them and 

 studying them in relation to their environment. 



Our course lay at first along the edge of the plains border- 

 ing the foothills, then gradually swinging outward through 

 the irrigated valleys to Greeley, then northward over the 

 higher plains, above reach of irrigating ditches, to Chalk Blufifs 

 eastward to Pawnee Buttes, back to Greeley by way of Crow 

 Creek and home by the shortest route. 



The great difference in conditions between the streams and 

 timbered valleys of the foothill region and the drv, treeless 

 plains of the northern area was nc ticeably marked by a change 

 in the avian fauna. Among the pines of the foothill ridges 

 were magpies. Long-crested Jays and Brewer Blackbirds, and 

 on the rocks of the f( othill slopes were innumerable Rock 

 Wrens, scolding and singing as we passed by. On dry, open 

 mesas adjoining the foothills between the streams Mourning 



