Vol i909' VI ] Roberts, Colony of Yellow-headed Blackbirds. 371 



A STUDY OF A BREEDING COLONY OF YELLOW- 

 HEADED BLACKBIRDS; INCLUDING AN ACCOUNT 

 OF THE DESTRUCTION OF THE ENTIRE 

 PROGENY OF THE COLONY BY SOME 

 UNKNOWN NATURAL AGENCY. 1 



BY THOMAS S. ROBERTS, M. D. 



Director, Department Birds, Minnesota State Natural History 



Survey. 



Plates V-XVI. 



In an effort to secure exact and detailed information in regard 

 to the nidification of the Yellow-headed Blackbird (Xanthorephalus 

 .ranthocephalus), a nesting colony of these birds was subjected by 

 the writer and an assistant to a continuous daily inspection for a 

 period of thirty-two days, from May 13 to June 13 inclusive, 1901. 

 The locality selected was a clump of quill-reeds (Phragmites 

 phragmites) about an acre in extent, isolated by open marsh from a 

 more extensive growth of reeds bordering a large slough which 

 forms part of the preserve of the Long Meadow Gun Club, lying in 

 the bottom-land of the Minnesota River and distant ten miles from 

 the city of Minneapolis, Minnesota. It was on the opposite side 

 of the slough from the buildings of the Gun Club, accessible only 

 by boat and in no way subject to intrusion by domesticated animals 

 of any sort. Observations were begun on May 13, and from that 

 date until June 13 the entire site was carefully examined once, and 

 often twice, a day, with the exception of three days — May 1(5 

 and 28 and June 6 — when severe wind and rain storms made it 

 impossible to reach the locality. 2 Each nest as it was found was 

 marked by an inconspicuous numbered tag attached to the reeds 



1 Read in part before the American Ornithologist's Union in Cambridge, Mass., 

 Nov. 18, 1908. 



2 A large part of the data forming the basis of this paper was secured through 

 the patient and careful cooperation of Miss Mabel Densmore of Red Wing, Minn., 

 who was quartered at the Gun Club and made the daily rounds of the Colony in 

 the absence of the writer. 



