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THE. C.IB .R olume XII Jul?-.?xu?ust, 1010 Number SOME COLORADO NIGHT HERON NOTES By ROBERT B. ROCKWELL WITH NINE PHOTOS BY THE AU'rHOR 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 bre?ding habits of the Black-crowned Night Heron (?ycticorax 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 which 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, hhd 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 wfis 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