DEFECTIVE CYCLES. 81 



Feb. 8. -To-night GF 1, for the first time since Jan. 20, takes her place on the perch 

 beside her mate. She went on the nest at first, but came off of her own accord. Thus ends 

 her incubation of an empty nest for a period of 20 days. The time is so nearly the same as is 

 usually given to eggs and young that there can be no doubt that she has taken a regular 

 course, just as if she had laid. On the following night GF 1 took the perch for the second 

 time. The male tried during the day to induce her also to build a nest, but she does little 

 as yet. 



SECOND CYCLE. 



After a normal mating period this pair repeated a part of their previous performance. 

 The female incubated for a week under the same defective conditions. This activity was 

 finally terminated by persistently driving her from the nest. 



Feb. 25. On Feb. 8, GF 1 ended her 20 days' incubation of an empty nest. On 

 Feb. 10 she paid more attention to the male and spent a short time on the nest receiving 

 straws. After taking the perch for 3 or 4 nights she began sitting again and, although 

 driven off every night, she followed it up for about a week; but on Feb. 19 she took the 

 perch again of her own accord. After taking the perch regularly every night from Feb. 19 

 to Feb. 24, she laid an egg this afternoon at the normal hour, between 4 h 30 m and 6 o'clock. 

 This is her first egg in life, and it comes after two premature rounds of sitting. She 

 laid a second egg after the usual interval. (R 19.) 



BLOND RING MALE AND WHITE RING FEMALE. 



This record presents some rather unusual and ambiguous features. The two 

 females W 1 and W 2 (St. alba) had been together previous to the record, and both 

 were nearly ready to lay. Since the two laid at practically the same time, there 

 being a difference of only one day, it is probable that we here have another case 

 of the pairing of two females resulting in the production of eggs on the part of both. 

 A male called X was introduced into the cage with W 1 two days before her first 

 egg, or five days after she had started on the reproductive cycle of activities. The 

 male attempted sexual advances and persisted in the sexual activity in spite of 

 the lack of an adequate response on the part of the female. The male's incubation 

 activity did not start with the advent of the eggs, but only upon the "cessation of 

 his sexual activity," i.e., after a normal period of 6 days. The female's incubating 

 activity persisted, although there was a lack of interchange with the male, and in 

 spite of the sexual advances of the latter. 



This male was later transferred to another female, W 2, who, like the male 

 at this time, was in the incubating stage of activities. But the two birds that had 

 separately attained and begun the incubating activity refused to continue it 

 together; the new mating broke the cycle for both, and a new cycle was initiated 

 almost immediately. It is thus probable that the continuance of incubation on 

 the part of the male depends to some extent upon a definite set of external con- 

 ditions, a particular female, nest, or nest-location, etc.; for a change from one 

 set of conditions to a very similar set of conditions was sufficient to break up the 

 activity. The female W 2 responded very quickly. Probably her discontinuance 

 of incubation was not due entirely to the solicitations of the male, since in the 

 pairs previously discussed it was frequently noted that the female effectively 

 resisted the solicitations of the male for long periods. A predisposing cause may 



