ANIMAL BEHAVIOR — WELLS 423 



ments, and how the new mood can be heard to intensify and then fade 

 away again — for all the world as if the bird were dreaming of fear or 

 food as it sang. 



There are lists of calls in Witherby's "Handbook of British Birds," 

 and the reader can hardly fail to notice a strong positive correlation 

 between the number of different notes assigned to each bird and the 

 thoroughness with which that species has been investigated. In "The 

 Wren," which is not only the name of a bird but also the name of a 

 recent important book about it by E. A. Armstrong, that author 

 enumerates 14 kinds of calls and 6 kinds of song, and he writes that his 

 account "is over-simplified and includes only the commonest and most 

 significant types of utterance." In the whitethroat, Dr. Sauer has 

 tabulated 25 different calls and 5 types of song ; and he finds that the 

 whole of this tremendous vocabulary appears in whitethroats reared 

 in isolation, in soundproof rooms, from the egg. In his own words, 

 "A bird lacking all acoustical experience, utters all these sounds in 

 exactly the same manner, in the same phases of its life cycle and in 

 the same specific moods as birds in the field." 



Dr. Marler tells me that his isolated chaffinches produced all the 

 calls perfectly normally, except for a slight peculiarity of one note. 

 According to Dr. Collias, the domestic chick can emit its usual distress 

 and pleasure notes even before it hatches. Cool the "pipped" egg and 

 you hear loud, protesting cheeps from inside ; warm it again, and they 

 are replaced by delighted twitterings. 



I have talked at some length about the vocal behavior of birds 

 because it is so easily observed. It is in fact meant to be observed, 

 being a method of communication. But birds do other things besides 

 emitting noises. They hunt for food, they fly about, they preen them- 

 selves and scratch, they continually interrupt whatever else they are 

 doing to raise their heads and look around for possible danger. May 

 it not be that the patterning of these activities is largely based, as the 

 vocal behavior so clearly is, on complicated inherent rhythms ? 



It is not easy to get clear evidence on this question. One would 

 expect an affirmative answer, for the following reason: the various 

 notes are often accompanied by characteristic movements of the bird ; 

 and in many cases, what is characteristic is not so much a particular 

 posture as a particular sequence of events which appear in other con- 

 texts — for example, an alternate raising and lowering of the head 

 feathers, or a moving of the body from side to side. Voice and move- 

 ment are intimately entangled, and it would be strange indeed if the 

 type of organization that is shown by vocal behavior were strictly 

 limited to that one activity. There are, in fact, several published 

 descriptions of what appear to be inherent rhythms in nonvocal 

 performances. Let us consider three examples. 



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