Drumming Flight in the Blue Grouse and Courtship Characters of the Tetraonidae

Abstract

An observer who has witnessed the courtship of various grouse can hardly help but become interested in their comparative actions. My interest in the courtship of the Tetraonidae has been aroused further by the drumming flight of the Blue Grouse (Dendragapus obscurus), to which but one reference has been found in the literature. I have had a number of opportunities to witness this drumming flight, but it was not until the spring of 1945, when I was in the field along the east side of the Blue Mountains above the Grand Ronde River near Troy, Oregon, that I was able to study it in some detail. These observations have led me to reexamine the courtship performances of our New World grouse from a comparative point of view. I have had opportunity to witness and study the courtship of all North American members of the Tetraonidae except Ptarmigan and Sage Grouse. For these, I have had to depend upon conversations with field men who have observed their displays, upon published descriptions and photographs, and upon still and motion pictures taken by fortunate observers. * The drumming flight of the Blue Grouse begins before dawn, often with a roar as the bird drops from its roost in a tree. Evidently the opportunity presented by the descent is utilized for drumming. From then on, all flights seem to be performed from the ground, at least' in the obscurus group; they cease about daylight and are taken up again late in the day. On April 3, 1945, I heard the first flight from the ground at 5:.58 a. m. (Pacific War Time) in the woods behind my tent, when the temperature stood at 29' F. and a trace of snow covered the ground. A Weston exposure meter registered 4 against the open sky above; it would not register in the dim light of the timber. The last drumming flight that night took place at 7: 14 p.m. when the sky reading was 6.5. The next day was clear, and grouse began drumming flights at 5:57 a.m. and stopped at 7:50 p.m. April 5, however, dawned cloudy; no grouse hooted or drummed until 6:45 a.m., and the last occurred at 7:30 p.m. The drumming flight is rather well known to ranchers, cowpunchers, and others who visit the breeding grounds of the Biue Grouse in spring. They generally describe it as "sommersaulting," which it proves not to be. I have watched the performance many times, both with and without binoculars. The birds initiate drumming from display or partial display posture between hooting. Although the birds hoot throughout the day in varying degrees, I have so far not observed drumming flight except in the morning or evening. There seem to be no preliminaries to the flight; the bird springs into the air, the wings beat rapidly and loudly as he rises, there is a pause as the bird coasts on set wings and starts to descend, then a last burst of the wings occurs as he approaches the ground. The sound of the wing beats may be rendered "burr-r-r-urrp." In. all cases that I have witnessed, the hooter reached a height of about a yard and alighted within a couple of yards or so of the starting point. Some flights rotate to the right, but most that I have seen rotate to the left in an arc of about 180". There may be some relation to wind, for one that I watched perform on the evening of April 27, 1945, rotated to the right against the wind and always reached ground behind and down-wind from his former position and facing the opposite way. Whether the head is always outstretched and held upward on the rise and downward on the descent, I am unable to