INCUBATION BEHAVIOR. 59 



roosts near the female on the nest at night, fondles her head when she is on the 

 nest, follows her to the floor, and attempts copulation, etc. The female is thus 

 forced to do double duty. In this connection an instance is noted in which "the 

 female is absolutely faithful and sticks to the nest, doing double duty, while the 

 male loafs about, occasionally visiting his mate and fondling her head without 

 showing a particle of interest in the little one." 



In a fourth case the incubation was normal from February 28 to March 15^ 

 shortly before the eggs were due to hatch. The male then began to sit irregularly 

 and attempted to entice the female to begin a new cycle. To prevent this the male 

 was removed from the cage early on the morning of March 16. After being on the 

 nest all night, the female remained on the nest all of the following day and during 

 the next night, a period of about 40 hours. On the morning of the 17th, the day 

 the first egg was due to hatch, she left the nest and refused to sit another moment. 



The female does not always do double duty when her mate fails to do his duty. 

 There would seem to be a limit to endurance. In the first cycle of a crested-ring- 

 dove pair whose record is given in Chapter VII, no eggs were laid. The female 

 persisted in incubating an empty nest for 20 days, while the male did not parti- 

 cipate. In this record it is noted that "she takes the nest at about the same time 

 that she would if she were alternating with the male." The same conditions 

 probably obtained in the second cycle of the same pair, and in two cycles of a 

 similar crested-blond-ring pair; while no definite statements are made, the fact 

 is emphasized that the female persisted in sitting at night. Sitting at night and 

 indifference to the male are regarded as the proofs of the contention that the 

 female was really going through the incubation stage of the cycle. 



In the hybrid-Zenaidura pair whose record is given in Chapters I and VII, 

 the male courted unsuccessfully for a month and then began incubation alone, 

 without eggs, and on the floor of the cage. The records state that "this male sat 

 steadily night and day" for a period of nearly 2 weeks. 1 



COPULATION. 



Copulation persists practically up until the first egg is dropped and it then, 

 or very soon after, ceases. Normally there is no courting or copulation during the 

 incubation period. When such activities are manifested by one bird, it is a sign 

 that it is attempting to renew the cycle. If both birds participate, a new cycle 

 begins at once and the eggs are deserted (see Chapter VII). However, one copu- 

 lation was recorded on the seventh day of the incubation period of one pair and 

 no disturbance of their incubation activities resulted. 



NEST-BUILDING. 



The nest-building which occurs during the mating period ceases during the 

 egg-laying period, but is resumed as soon as alternation of sitting begins. The 

 "free" bird spends much time in carrying straws to its sitting mate. At first the 



1 Some males are so hyperdeveloped in the tendency to sit that they hardly give the females a chance. 

 (Conv. W. C.) 



