CHAPTER IX. 



REPRODUCTIVE CYCLE SUMMARY AND ANALYSIS. 



The present chapter attempts, for the convenience of the reader, an editorial 

 summary of the various facts, principles, and interpretations of the previous 

 material, with occasional additional comment and suggestion. The reproductive 

 cycle may be conveniently divided into four groups of activities whose temporal 

 relations are represented in figure 1. The sexual activities are represented by M; 

 N and F refer to the nesting and feeding activities respectively; while / stands 

 for the incubation of the eggs and young. The variation in thickness expresses 

 the gradual rise of the impulse to its maximal strength and its gradual decline and 

 final disappearance. The length of the lines expresses the relative duration of the 

 activities, each unit of length representing a day. Since these periods are highly 

 variable in length, we have arbitrarily chosen values which approximate an average. 



DESCRIPTIVE SUMMARY. 



(1) The sexual activities extend over a period of 7 days. They are difficult to 

 describe in any fixed temporal order, since the composition and order of events seem 

 to vary with the state of excitement, the reciprocal response of the mate, and the 

 general progression of events in the cycle. The same bit of behavior may occur 

 in several connections and have a variable meaning and purpose. Only a logical 

 analysis and summary of the simpler elements of behavior is possible. The prelim- 

 inary acts mentioned are billing or pecking at their own feathers on the wings and 

 certain parts of the tail; preening and shaking the feathers; elaborate bowing and 

 cooing; going to the nest and giving the nest-call; approaching the mate; giving 

 amorous glances; wagging the wings; lowering the head; swelling the neck; raising 



^ I 



FIG. 1. M, mating period; N, nesting activities; I, incubation of eggs and young; F, feeding of young; 



M 2 , mating period of second cycle. 



the wings; raising and spreading the tail and feathers on the back and rump; 

 alternately stamping and striking the feet and wagging the body from side to side, 

 and strutting with drooping wings. Charging and driving may be resorted to 

 in the courtship. The male walks or rushes at the female, holds the head high, 

 lowers the wings, exhibits excitement, elevates the back, erects the feathers, pecks 

 perfunctorily or petulantly, clucks, and gives the driving coo consisting of three 

 notes, 1 with raised wings, raised and spread tail, while the beak is on the floor. 



1 This and some other features of behavior apply particularly to bronze-wing pigeons. EDITOR. 



93 



