RUFFED GROUSE 147 



tween the ' thumps ' the wings of the bird register on the film with 

 scarcely a blur representing the intervals between thumps. The 

 varying tempo of the intervals between thumps has been noticed 

 by all observers and as registered on the film is as follows, each 

 number being the number of pictures or the number of sixteenths 

 of a second between thumps : 



5_6_8-S-fr-5-5-4-^3-3-3-2r-2-l-2-l-l-l-l-l-l-000000000000000000000-l. 



"If one now examines the series of pictures he will see that not 

 once is the back blurred, as it would be if the wings struck behind 

 the back, and that wherever the wings have moved with sufficient 

 rapidity to cause a compression of the air and resulting sound, they 

 are registered forward and upward. This then is the effective sound- 

 producing stroke of the wing — forward and upward — not outward 

 and upward as stated by Sawyer — more like his inward and forward, 

 which he says is silent or nearly so. 



" Moreover, if one watches the tail of the grouse during the drum- 

 ming performance, he will see it become more and more flattened 

 against the log, for 'action and reaction are equal and opposite in 

 direction ' and the forward-upward stroke of the wings tends to drive 

 the bird backward and downward on its tail. The reaction that 

 follows cessation of drumming is even more clear to the observer, 

 for always, upon the completion of the drum, the bird pitches slightly 

 forward and the tail lifts from the log as if it were a spring under 

 compression ; when the pressure is suddenly released by the cessation 

 of drumming, the tail throws the bird forward and upward and is 

 itself carried upward by the impetus given the bird. 



"A single weak thump heard at the conclusion of the drum registers 

 on the film in frame 122 after an interval of one frame where the 

 wings are quiet. It corresponds to the beginning ' thump ' and is 

 given as the bird pitches forward and is in a more horizontal position. 

 This stroke is forward and downward rather than upward and 

 perhaps helps the bird to regain its balance. 



" During the four nights and mornings spent in the blind the 

 grouse drummed approximately one hundred times. I am frank to 

 confess that I did not watch every performance, for the strain of 

 keeping one's eyes at a peephole is considerable in the small hours 

 of the morning. I did watch most of the performances, however, 

 until I was absolutely convinced that the sound was produced as 

 here set forth." 



Nesting. — The ruffed grouse is a woodland bird, and its nest is 

 almost always in thick woods or under dense cover, though I once 

 found a nest in a fairly open situation; it was placed at the base 

 of a small white birch in a clearing, with only a few small trees 

 and bushes near it. Most of the nests I have seen in Massachusetts 



