444 BULLETIN 191, UNITED STATES NATIONAL MUSEUM 



bushtit is 12 days, the young hatching on the 13th. Based on her study 

 of two nests, Mrs. Addicott (1938) makes the following statements: 



Incubation apparently is started on the day the last egg is laid, or on the day 

 before. The burden of incubation seems to be shared equally by the male and 

 female. * * * On cold days the eggs are incubated almost constantly, the parents 

 alternating about every ten minutes on the nest. On warm days much shorter 

 periods are spent on the eggs, and the parents forage together to some extent. 

 Both birds spend the nights in the nest. 



The young are naked at hatching and down does not develop. The eyes are 

 closed and remain closed at least through the seventh day. 



The young are fed solid undigested food from the first day on, and lepidopterous 

 larvae are carried into the nest a few hours after hatching. 



During early stages the young are brooded and fed as much by one bird as the 

 other. Toward the end of the period, one parent does about two-thirds of the 

 foraging and feeding. The mate spends most of the time moving about in the 

 nest tree. The young apparently leave the nest on the fourteenth or fifteenth 

 day. They become independent of the parents within eight days after leaving the 

 nest, but have been seen to feed themselves on the day of nest-leaving. 



She says that while the young are being fed in the nest "feeding 

 occurs from eight to twelve times an hour" and that the "fecal sacs 

 were carried as far as fifteen feet from the nest." Of the behavior at 

 the time of nest-leaving, she writes: 



When the nestlings are ready to fly, the slightest disturbance sends them out 

 of the nest. As one juvenile starts to leave, the impulse apparently spreads rapidly 

 to the others. So quickly do they pop out of the nest, that one has the feeling that 

 the nest has suddenly exploded. There is an incessant medley of Juvenal trills. 



The jirveniles fly a little awkwardly and to a lower level when they leave the 

 nest. They scatter in all directions, often alighting in the grass, uttering the trill 

 all the while. The parents immediately become excited, uttering a rapid suc- 

 cession of alarm notes as they dash from one young bird to another in an evident 

 effort to protect them and to get them together. This is quite a task, for the 

 juveniles fly as far as twenty-five yards from the nest tree. 



The parents spend from fifteen minutes to half an hour gathering the scattered 

 family in low bushes or in a small tree. * * * Half an hour after nest-leaving the 

 young start following the parents in their search for food, begging with trills as 

 they go. * * * 



As soon as the juveniles are able to fly well enough to follow the parents, the 

 family moves about in typical flock formation, the parents doing all of the foraging 

 for the young. This takes place at least the day after nest-leaving, and fre- 

 quently only a few hours afterward on the same day. 



* * * Feeding by the parents is continued from eight to fourteen days. One 

 family was fed till the eighth day after leaving, when two of the juveniles were 

 seen foraging for themselves, clumsily hanging upside down in search of food. 

 It seems likely that the shortness of the juvenal tail makes this process difficult, 

 since it has been observed that it is impossible for an adult without a tail to do 

 this. * * * 



Begging and feeding were observed in another family up to the fourteenth day 



