THE REACTIONS OF BIRDS TO SOUND STIMULI 211 



later, when I tapped on my note-book cover with my pencil, 

 the bird looked about over its head as if trying to discover the 

 source of the sound. 



During the afternoon I tried the effect of song on the bird, 

 but I obtained no positive results. I did notice, though, that 

 if the song were suddenly broken off and two or three sharp 

 raps given on the tent pole, the bird reacted more vigorously 

 than to the raps alone. And a suddenly ended loud sound 

 seemed to startle it more than a sudden loud sound did ordinarily. 

 These reactions were noticed several times during the afternoon, 

 but they became much less marked on successive repetitions 

 of the experiment. 



July 12, 9:25-10:40 a. m., 1:10-3 p. m. The bird seemed 

 very uneasy at noises made outside the tent, particularly at 

 the loud cawing of some crows. After about half an hour of 

 quiet, I blew a loud blast on the whistle, which produced only 

 a slight reaction. The squeaking sound made by kissing the 

 back of the hand vigorously produced no visible reaction. The 

 higher pitched of the two whistle notes, when sounded alone, 

 seemed to produce a slightly more vigorous reaction than did 

 the lower one alone. But no whistle blast produced so strong 

 a reaction as did the sudden loud call of a cuckoo from the 

 near-by aspens. 



The visual stimulus produced by a moving object seemed very 

 much stronger than did any auditory stimulus; when I showed 

 my fingers at the aperture the bird showed very decided alarm. 

 As the experiment was repeated the reactions became much less 

 pronounced. 



In the afternoon I took a mandolin to the tent; and, as with 

 the whistle, the notes of higher pitch seemed to produce slightly 

 more vigorous reactions. However, the differences in the reac- 

 tions were so slight that it was very difficult to make such 

 determinations. The notes used ranged over about two octaves, 

 from the open G-string of the mandolin to B two octaves higher. 



I found that a chord produced a more vigorous reaction than 

 did any single note; however, the bird quickly became ac- 

 customed to the chord, and after half a dozen trials merely 

 showed increased vigilance. As on July 10, I found that if 

 a sound was interrupted by another of very different character, 

 a more vigorous reaction was produced than by mere suddenness 



