1916 J HvxhEY, Bird-ivatching a7id Biological Science. 157 



relations of display and coition are concerned, is found in such 

 birds as most Finches. These are monogamous, and the male 

 only goes through a display. But here there is almost always 

 sexual dimorphism, the cocks often being very brilliant, and the 

 brilliant colors are so arranged that they are especially well shown 

 during display. Here then some agency must have been at work, 

 adding to the primitive display of the Warblers, and making it 

 more effective as a stimulus to the hen. 



These three different courtships give us, as I believe, the key to 

 the general problem of courtship in birds. To me, that key con- 

 sists in this: — that under the one term "Courtship" are included 

 two entirely different sets of activities. In the first place, there 

 are such activities as are shared equally by the two sexes — cere- 

 monies and actions, often elaborate, performed for the pleasure 

 and the joy of the performance; and secondly, there are ceremonies 

 of the nature of a display by one sex only. I would prefer not to 

 have to give special names to these two distinct sets of activities 

 until I have more facts and more fully-digested facts; but to 

 distinguish between them, I propose here to give the name of 

 Display Courtship or Darwinian Courtship to the second set of 

 activities; and to the first, which has scarcely received any of the 

 attention it deserves, either from Darwin or subsequent authors, 

 I shall give the name of Mutual Courtship. 



As far as I can see, the underlying physiological bases for these 

 two forms of courtship are to be found in the inherited sexual 

 temperaments, if one may so call them, of the two sexes. In some 

 birds, the male is much more eager than the female, and it is in 

 these that Display Courtship has developed. The basis for 

 Mutual Courtship lies in a similarity of sexual temperament in 

 both sexes — neither markedly more eager nor more reserved 

 than the other. 



Furthermore, the immediate function of courtship is twofold. 

 Either form of courtship may have both functions; it may serve, 

 first, as a stimulus to coition (in Mutual Courtship the pair is 

 worked up, in Display Courtship the male works the female up to 

 the necessary point of exaltation); and secondly it may serve as a 

 bond to keep the pair together. 



In mutual courtships, the tendency is to drop the first function 



