144 BULLETIN 162, UNITED STATES NATIONAL MUSEUM 



and I was instantly reminded most forcibly of the pictures one sees of that 

 singular family of birds, the penguins. Now the wings were drawn slightly 

 back, a quick stroke given forward, at the air, and a pulsating throb entirely 

 different from any sound I have ever heard, struck my ear, producing at such 

 short range an almost painful sensation on the drum ; the wings were immedi- 

 ately recovered, and another stroke, a trifle quicker than the first, was succeeded 

 by another still quicker, until the wings vibrated too fast to be followed by 

 the eye, producing the well-known terminal "roll of muffled thunder," and 

 not till then the " semicircular haze." I say not till then, for the first two or 

 three strokes could be distinctly followed by the eye. This over, the bird 

 immediately rose to its feet, shook its feathers with an air of relief, and 

 resumed its attitude of repose. * * * 



I think the drumming of the ruffed grouse is produced by the forward beats of 

 the stiffened wings on the air, the planes of their motion being nearly horizontal, 

 about four inches in length, with the initial ends represented by the points 

 of a wire passed through the center of the erect body from side to side. 



" Brewster's explanation of the drumming seems to have been 

 rather generally accepted until 1905. At that time Prof. C. F. 

 Hodge, of Clark University, was experimenting in the rearing of 

 grouse in captivity and enjoyed exceptional opportunities for 

 watching the drumming performance at a distance of but a few feet 

 and made 40 different photographs of the drummer. He published 

 quite an extended account of this drumming with his conclusions and 

 a number of his photographs in the Country Calendar (Hodge, 

 1905). He states: 



As to the matter of interpretation, I can not entirely agree with Professor 

 Brewster. The appearance to the eye, however, supports his theory that the 

 wing strikes nothing but air. But I am convinced that at just the critical 

 moment, when the sound is produced, the wing moves with too lightning-like 

 rapidity, even in the first slow sti-okes, for the eye to follow it. The wing, 

 consequently, disappears from sight as it approaches the contour surfaces of the 

 feathers of the sides. We must defer here to the eye of the camera, and some 

 of the photographs certainly show the blur of the rapidly vibrating wings coming 

 up and touching the tips of the feathers along the sides. It is the impact of the 

 stiffly held concave wing on the feather cushions of the sides that causes all the 

 sound. In fact, the sound, so far as quality goes, can be best imitated by 

 striking with a wing properly stretched, or even a concave fan, on an extremely 

 light eider-down cushion. 



" The next account which should be included is that of Frederick 

 K. Vreeland reporting in Forest and Stream, for April, 1918, and 

 reprinted in the Bulletin of the American Game Protective Associa- 

 tion. After watching a grouse drum at a distance of 6 feet and after 

 taking a remarkable series of photographs of the drumming bird, he 

 came to the conclusion that the thumping sound was produced by the 

 wings striking behind the back, and he introduces a photograph thai 

 he says ' will prove to the most skeptical that they (the wings) did 

 actually strike behind the drummer's back.' 



