106 BEHAVIOR OF PIGEONS. 



acts persist when no necessity is present, for the birds are forced to choose their 

 old and ready-made nests. The impulse to seek a new site is manifested even 

 when there is no opportunity for gratification. This tendency to seek the site in 

 a new locality can be correlated with the advantage accruing from the resultant 

 weaning of the previous set of young. Both parents may be feeding at this time 

 and the previous young may not yet be entirely weaned from the nest. If the old 

 nest be utilized, the second cycle may be disrupted in this manner. Such an inci- 

 dent is reported in Chapter VII. Results, however, can not explain the existence 

 and mechanism of the tendency. One would need to conceive this behavior some- 

 what in the light of a negative reaction to the old environment. 



In the matter of the selection of a site, we can do little but ask a number of 

 questions indicating the problems involved. What are the objective conditions 

 necessary to the satisfaction of the birds? Must the seeking impulse run a certain 

 temporal course before it can be satisfied, and is it then easily satisfied by almost 

 any condition present at the time ? Which bird takes the initiative in the selection ? 

 Must the impulse run a certain time in each bird independently of the other? 

 The records make it probable that one bird may become satisfied with a site while 

 the other remains undecided for some time. If they do not influence each other 

 as to the time of choice, do they influence each other as to what the site shall be? 

 And which of the pair exhibits the greater initiative in this regard? 



Evidently the two tendencies do as a matter of fact become harmonized and 

 adjusted to each other; little can be said, however, as to the means by which this 

 is accomplished. Is the choice purely instinctive, or is it highly adaptive to vari- 

 able conditions? To what extent may experience play a part? The impulse can 

 adapt itself to changed conditions, as is evident from the final selection of the old 

 site and the adoption of a ready-made nest which, in many of the species studied, 

 is far removed from the sort of nest used under natural conditions. The nest- 

 constructive acts are highly instinctive, being observed in a young bird when 

 resting on the floor. It is suggested that the stimulus to these movements is the 

 uncomfortable contact situation which the resultant acts relieve. 



SEXUAL ACTIVITIES. 



The nature of the objective stimuli in the sexual activities has been discussed 

 under the topic of mating preference. A disposition is also present here, since 

 the acts are not always manifest when the objective conditions are present. The 

 impulse arises in part spontaneously and automatically, but it is also stimulated 

 to some degree by the persistent advances of the mate. The stimulating influence 

 of the mate is made evident by several instances, cited in Chapter VII, in which 

 the male was able to disrupt the cycle and entice his mate into sexual relations 

 within a few days. The sexual passion further develops from its own expression 

 and from the reciprocal stimulus of the mate. Without expression the cycle may 

 not develop further, or the sexual period may be greatly prolonged before incubation 

 is aroused. 



