1919 ] Tuttle, Drumming of the Ruffed Grouse. oo7 



essentially the same, and produced in the same way as the roar 

 which accompanies the flight of the Grouse when startled (that is, 

 by the action of the wings on the air), is perhaps an unsatisfactory 

 explanation of that far-away throbbing challenge which steals on 

 the ear so subtly, like the half heard beating of one's own heart. 

 Yet for want of further evidence it must serve. What I should 

 most like to discover is to how great an extent inflation of the 

 rudimentary tympanum serves to enhance the strenuous thrust 

 of the wings which seem to catch the air at the well feathered flanks. 



Most of the Tctraonidce are possessed of air sacs, located under 

 the neck tufts or ruffs, which when inflated are capable of pro- 

 ducing a booming sound of great carrying power, which may be 

 heard while the birds are performing their amatory dances, and it 

 does not seem to me at all impossible that the sound-carrying 

 powers of the drumming of Bonasa may in part be traced to an 

 inflation of the rudimentary sacs which it possesses. In this 

 connection observation alone is of little service, though I noticed 

 that in the pause which follows the preliminary wing beats (which 

 have but little sound- carrying power) that the contour of the bird 

 changes perceptibly, the throat and the region of the ruffs is 

 apparently swelled, and the next wing beat comes with increased 

 volume. Mindful of what effects a bird can produce simply by a 

 change in the arrangement of his plumage, I am inclined to think 

 that this "swelling" is of an inflated character. Audubon, by 

 puncturing the air sacs of a captured Pinnated Grouse, satisfied 

 himself that these appendages were the source of the "booming," 

 and perhaps some such experiment with a captive Ruffed Grouse 

 would prove to what extent inflation of these parts plays in the 

 ventriloqual and resonant quality characteristic of this bird's 

 exuberant drumming. 



But. to me the most significant feature of the drumming is not 

 the question as to the source of its sound-carrying powers, nor the 

 attitudes that the Grouse assumes, though they are interesting, 

 but it is the evidence of the compelling power of habit. (This 

 differs greatly in individuals, and I here confine myself to the 

 individual studied during the spring of 1918.) In spite of the 

 disturbances which occurred owing to my presence in the blind, 

 in spite of the obvious annoyance of the blind itself, especially 



