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Volume XI 1 
July- August, 1910 
Number 4- 
SOME COLORADO NIGHT HERON NOTES 
By ROBERT B. ROCKWELL 
WITH NINK PHOTOS BY THR AUTHOR 
D URING the spring of the years 1906, 1907 and 1908, a happy combination of 
circumstances made it possible for the writer to spend a portion of each 
week at Barr, a station nineteen miles northeast of Denver, Colorado, study- 
ing the abundant bird life along the chain of reservoirs and seepage ponds, which 
extends from this point several miles to the northeast. During the time I workt 
in this field I was the guest of, and was accompanied by, Mr. L. J. Hersey, to 
whom I wish to express my appreciation for the convenient opportunities for field 
work thus afforded. 
During these three seasons I was greatly interested in the breeding habits of 
the Black-crowned Night Heron ( Nycticorax nycticorax naevius ) and spent much 
time observing them. The result of these observations, together with some sup- 
plementary work done at other times and places, may prove of some interest to 
Condor readers. 
My first experience with the Night Heron as a breeding bird was the discov- 
ery of eighteen birds in a colony of Great Blue Herons wdiich occupied a small 
clump of very tall cottonwoods on the St. Vrain River not far from the town of 
Lyons, Colorado. This was on April 21, 1906, and at this date only one pair of 
the Night Herons seemed to have located a nest, altho the remaining eight pairs 
were apparently busily engaged in selecting nesting sites. 
All of the nests in this rookery were practically inaccessible, being bilt amid 
the slender topmost branches of the tallest trees, and this fact, coupled with what 
I had read in various text-books, had created the impression in my mind that the 
Night Heron was strictly a “tree-nesting” bird. 
It was, therefore, with some surprise and not a little incredulity that I was in- 
formed some six weeks later that a good-sized colony of these birds was breeding a 
few miles below Barr in a cat-tail swamp, the nests being placed upon or near the 
