360 Roosevelt Wild Life Bulletin 



tained by the one motion offsetting the next. Thus a rowboat will 

 remain in one place if the oarsman attempts to row forward and 

 backward, alternately, without turning his oars or raising them from 

 the water. On first thought one might well doubt that a grouse 

 or any other bird could extend its wings with sufficient force to 

 produce a " thump " on the air audible for several hundred feet 

 and even several hundred yards. I was so strongly inclined to this 

 doubt that the bare possibility of the thing was a long while in 

 occurring to me at all ! Yet, seeing the feat actually accomplished 

 over and over again, I now know it to be a fact. Note, however, 

 in this connection, the force with which domestic pigeons and cer- 

 tain other birds strike their outward blows with their wings in 

 fighting. 



I believe I am fully prepared to state that the drumming is caused 

 by the wings striking the air, alone. Whatever part in the sound 

 may be taken by any other part of the bird than his wings must 

 be very slight and merely incidental. In support of this statement 

 attention is directed to the accompanying photographs with their 

 explanations. The stiff primaries give forth the loudest part of 

 the sound; the soft innermost secondaries, the least. The entire 

 " thum " of each wing-beat is simply the total sound from all the 

 wing feathers heard in unison. All bird students of any considerable 

 experience, and hundreds of others, have occasionally seen a bird 

 suddenly flash out its wings on the impulse of some alarm, the 

 sound produced by this action sometimes being audible for several 

 yards. The motion in this gesture is about the same as that of 

 the drumming Grouse. Even in the silence with which the fright- 

 ened bird brings its wings back to rest, upon finding the alarm 

 was false, there is a likeness to the case of the Grouse. After the 

 outward and upward motion in each beat, as long as the eye can 

 clearly follow these the wings seem almost to fall of themselves 

 or to rebound from the impact on the air in the upward stroke, 

 then hang limp from the bend of the wing, often with a quite per- 

 ceptible pendulum motion, until the next upward flash (figure 98). 



When about to drum the Grouse usually sets his feet carefully 

 as a man does in preparation for a standing broad jump (figure 99). 

 But first the bird is likely to turn around completely once or twice 

 as if bent on trying a new direction (figures 100, 101). Grouse 

 No. 1, for example, had the habit of frequently doing so, always 

 ending up quite comically by facing the same old way when he 

 began to drum. That is the rule almost without exception ; each 

 drumming log is a one-way affair in that respect. For instance, 

 logs No. 1 and 2 pointed in the same direction; yet the Grouse 

 always faced west on number 1 and east on number 2 when drum- 

 ming (figures 102, 103). The turning around reminds one of the 

 similar acts of dogs before finally lying down just where they 

 started. 



Now, with the first preliminary wing-beat, the body of the drum- 

 mer snaps into a more upright pose, the neck and chin feathers 



