lyS THE BIOLOGY OF BIRDS 



thus the sex-impulses, which are usually satisfied for the 

 time being in about a week, after which comes the period of 

 egg-laying and incubation, may be prolonged. It is also 

 noteworthy that a female domestic pigeon may pass to nest- 

 building, egg-laying, and incubation without the stimulus of 

 a mate, but the unfertilised eggs come, of course, to nothing. 



While it is normal for the male to take the initiative, the 

 rule is often broken. In connection with this and with the 

 futile mating of two females, it must be noted that " sex- 

 intergrades " often occur among pigeons. Professor O. 

 Riddle (19 14) has made a study of extremely masculine 

 females. These relatively abnormal forms point the way 

 to cases like the Phalaropes, where the female birds normally 

 take the initiative in courtship and the males do most of the 

 incubation. 



The preliminary acts which Professor Whitman studied 

 in male pigeons are thus summarised by the editor, Dr. 

 Harvey A. Carr (1919, p. 93) : " 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 ; approach- 

 ing the mate ; giving amorous glances ; wagging the wings ; 

 lowering the head ; swelling the neck ; raising 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 [in 

 bronze-wing pigeons] of three notes, with raised wings, 

 raised and spread tail, while the beak is on the floor." 



This summary is too much like a composite photograph : 

 it blurs the fact that the behaviour is often in a marked degree 

 specific for particular kinds. Thus male mourning-doves 

 (Zenaidura) and some others stamp with their feet before 

 their desired mates ; the male bronze- wing stands on tip-toe, 



