W. H. THORPE 87 



ing, even for a short period in November, can effect the same kind of 

 result as the normal song experience of a wild bird in the field during the 

 autumn. Similar positive results were obtained in similar experiments 

 with re-articulated songs carried out in 1956-57 and 1957-58. Figs. 7 and 

 8 show such a re-articulated model and its effect on the song of a hand- 

 reared isolate. Hand-reared birds show similar differences from the wild- 

 caught ones, in that if given a reversed song a considerable amount of 

 copying is achieved. Similar experiments with other birds provide 

 further evidence for a previous conclusion that although a hand-reared 

 isolate is incapable by itself of producing anythhig approximating to a 

 normal ending, yet if once it hears a normal end-flourish on the 'song 

 tutor' (even though in the rearticulated song on the tape it occurs at the 

 beginning or in the middle of the song) it will recognize it as appropriate 

 for an ending and will attempt to place it properly in its own song. 



In experiments in 1954-55 ^-i^ attempt was made to indoctrinate hand- 

 reared isolate chaffinches with the song of the tree pipit {Ainliiis trivialis) 

 (Fig. 9), this being chosen because the spectrograph reveals that the tonal 

 quality of the notes is similar to that of the chaffinch. The i:irst experiment 

 gave a doubtful result, but a repeat in 1956 resulted (Fig. 10) in the 

 achievement of a remarkably good copy by such a chaffincli of the song 

 of the tree pipit, producing a chaffinch song entirely unlike any other 

 uttered in my experience by a wild or hand-reared bird. It is of interest to 

 note that the rather long song of the model has been condensed to conform 

 to the standard length of chaffinch song by condensing the middle phrase 

 of the tree pipit song to two notes instead of tour. This song became still 

 further 'tightened up' and shortened by the beginning of May (Fig. i i). 



The reason why chaffinches do not imitate and acquire songs from other 

 species in the wild now seems fairly evident. There is little doubt that they 

 restrict their imitativeness to the right models as a result of being respon- 

 sive only to notes of approximately the right tonal quality. It is interesting 

 that the imitation of the tree pipit song just referred to is the best copy of an 

 alien song so far obtained. Here the tonal quality of the model was right, 

 although the song itself was much too long and the phrasing of the notes 

 of the model abnormal from a chaffinch point of view. 



To summarize this work with the 'song tutor', it can be said that in 

 eleven experiments carried out over the years 1955-57 a-i^d involving 

 thirty-four wild autumn-caught first-year males, the only positive effect 

 obtained (in the sense of a significant similarity between model and 

 mimic) occurred in two experiments (seven birds) only, and in these two 

 the model was a normal chaffinch song. Of the remaining ones (nine 



