PUKl'OSK OF SONG 143 



through wliicli tlie KX6fl are brought into 



contact. 



Well now, we come hack to the question, 

 why, if all species have a serviceable recognition 

 call, that call should not he sufficient for the 

 purpose, just as, without a doubt, it is adequate 

 for all purposes at other seasons ? The answer 

 is, 1 think, clear. The recognition call is not 

 confined to one sex, nor only to breeding birds ; 

 it is the common property of all the individuals 

 of the species, and if the female were to rely 

 upon it as a guide she might at one moment 

 pursue another female, at another a non- 

 breeding male ; she might even be guided to a 

 paired female or to a paired male, and time 

 would be wasted and much confusion arise. So 

 that no matter how much a male might advertise 

 himself by cries and calls which were common 

 alike to all the individuals of the species, it 

 would not assist the biological end which we 

 have in view. Something else is therefore 

 required to meet the peculiar circumstances, 

 some special sound bearing a definite meaning 

 by which the female can recognise, amongst the 

 host of individuals of no consequence to her, 

 just those particular males in a position to breed 

 and ready to receive mates. Hence the vocal 

 powers, the power of producing sounds instru- 

 mentally, and the power of flight, have been 

 organised to subserve the biological end of 

 "recognition/' 



And this view is strengthened, it seems to 

 me, by the erratic behaviour of certain species, 



