THE EVOLUTION OF BIRD-SONG. 



245 



From Sept. 18S7, to 1st April, 1888. 

 Number of Redbreasts 

 Total of phrases . . . b90 



From 1st April, 1888, to August, 1888. 

 Number of Redbreasts . . 16 



Total of phrases . . .426 





Birds imitated. 



Percentage of 



imitations in total 



of phrases. 



Percentage of 



imitations in total 



of phrases. 



Amount of change 

 per cent. 



Chaffinch* 



•A 



11 



2-9 decrease. 



Lark 



7-9 



5-3 



2-6 



Accentor 



6 



4-9 



1-1 



Wood Warbler ... 



2-9 



4-9 



2 increase. 



Blackcap 

 Willow Warbler... 



3-3 

 •6 



6-3 



5-8 



3 



5'2 



In comparing the phrases of the Thrush heard in the first 

 months of the year with those heard in May and June, a change 

 of song, similar to that shown in the first table is noticed ; and 

 we find that in the latter period the Blackbird's alarm is, pro- 

 portionately with the other imitations, much less often uttered ; 

 while the reproduced notes of the Cuckoo, Wood Warbler, and 

 Butcher-bird (or Wryneck t) then become much more frequent. 

 In order to avoid a possible wish to discover certain notes in the 

 songs of birds, that might have biassed my judgment, I did not 

 until a few months since make any numerical calculation about 

 my records. 



In recording imitations I used phonography, in which the 

 names of birds imitated were at once written, and often the 

 names also of some of their cries, such as the House Sparrow's 

 "tell-tell" or " philip," or the Warblers' "tewy," which, like 

 many other notes, are invariable and easily recognised. Some 

 imitations are more easily recognised than others, either on 

 account of the character of the voice of the singer or that of the 

 note reproduced. Full voices cannot easily produce harsh notes ; 

 and the cries of certain widely distinct species are so much alike 

 as to defy accurate recognition when mimicked. On the other 

 hand, a small percentage of the imitations recorded by me were 

 exact reproductions. 



Birds that sing long imitative phrases (e.g. Starling, Sky 

 Lark, Sedge Warbler) often utter in one phrase a succession 



* "Chaffinch" here denotes all the cries of the Chaffinch, most of 

 which are uttered during winter. 



f The call-notes of the Butcher -bird and Wryneck are similar. 



