422 ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 6 



a series of little song phrases at extremely regular intervals, often 

 of about 10 seconds. The chaffinch is one of these, and there are many 

 equally familiar examples — the hedge sparrow, the yellowhammer, the 

 willow warbler, the robin, and so on. Even in those birds whose songs 

 seem, at first hearing, to consist of long ramblings rather than compact 

 phrases, the utterances show a more-or-less regular and characteristic 

 punctuation. The spacing of bird song seems to have received less 

 attention than the structure of the individual phrases. There is how- 

 ever a mine of exact information in E. M. Nicholson's admirable book, 

 "Songs of Wild Birds," and the regularity of the rhythms which his 

 timings reveal, in species after species, is indeed impressive. 



One would expect such timing to be basically innate. Dr. Peter 

 Marler tells me that the chaffinches reared in isolation at Cambridge 

 sang at about the usual intervals. The rhythms are of course by no 

 means inflexible. A chaffinch will sing at shorter intervals at one 

 time than at another, and for many months in the year it hardly sings 

 at all. Each bird has its preferred time, of day, when it sings most 

 frequently. In the great tit, as Dr. K. A. Hinde has recently shown, 

 the frequency of singing may vary from minute to minute. But 

 many plainly spontaneous rhythms in animals can fluctuate and be 

 modified according to circumstances — the heartbeat, for example — 

 and these variations do not exclude the view (which I think is ines- 

 capable) that the timing of bird song is based on an inherent, auto- 

 matic rhythmicity. 



The essential spontaneity of bird song is beautifulfy brought out 

 in the following passage from Mr. Nicholson's book : 



A song, in fact, needs no immediate stimulus to set it in motion (such as 

 fear, anger, hunger or isolation) nor does it call for any special reply. A cock 

 bird may sing better if more cocks are singing within earshot, but on the other 

 hand, he will go on singing for weeks at the right season with no other songsters 

 within miles of him and without a mate. We might even say that any bird sound 

 usually uttered in response to a specific and immediate stimulus is probably not 

 true song. 



As everybody knows, true song is only one item in a bird's vocabu- 

 lary, and most species have a wide repertory of different calls. Some 

 are brief outcries in response to a sudden stimulus — alarm calls at 

 the approach of a hawk, for example — but many of them are repeated 

 for considerable lengths of time in more-or-less regular rhythms, and 

 indicate the mood of the bird. Dr. Sauer has illustrated this very 

 beautifully in the case of the whitethroat, and gives many descrip- 

 tions of the mood notes and of the manner of transition from one mood 

 to another. He tells, for example, how a whitethroat in winter, sitting 

 quietly and singing its subdued and nearly continuous subsong, may 

 suddenly begin to interpolate among the song phrases the notes of 

 mild alarm or mild hunger, often accompanied by appropriate move- 



