462 BULLETIN 2 3, UNITED STATES NATIONAL MUSEUM 



daily observation at Yorktown Heights, N. Y. I saw the male bird 

 deliver several green larvae to the female while she was on the nest 

 incubating the eggs, but this is not of common occurrence as far as 

 I have been able to determine. 



The incubation period of two nests studied in Maine was 12 days. 

 The exact incubation period of 76 eggs in 21 Michigan nests was deter- 

 mined by Hann (1937). He found the time raiiged from 11 days and 

 12 hours to 11 days, with an average of 12 days and 5.6 hours. He 

 states that all the eggs of a clutch including the last had about the 

 same incubation period, and any variation of more than a few hours 

 usually concerned all. He found no difference in incubation time 

 with respect to warm or cool weather. 



The eggs may hatch at any time during the day but rarely at night. 

 They are pipped on the day before hatching. The shell cracks at 

 right angles to the long axis of the egg before the shell opens to allow 

 the young to emerge. 



Young. — The young at the time of hatching have their eyes sealed 

 shut but they readily respond to sounds as soon as they emerge from 

 the Qgg. TNHien extending their heads and opening their large mouths 

 they seem to balance themselves by their wing tips and sprawled-out 

 legs. Between feeding the young are brooded by the female, and at 

 this time she is very reluctant to leave the nest, even allowing a person 

 to stroke her feathers. 



The male assists in the feeding of the young at the very start, in 

 fact he may be seen at the nest even before the young have emerged, 

 in apparent anticipation of his domestic role soon to follow. The 

 adults walk to the nest in bringing food, usually along well-estab- 

 lished routes and runways which in part are concealed from view. 

 They often stop with food in their beaks, when near the nest, and 

 carefully scrutinize the surroundings as if to make sure they are not 

 being spied upon by some intruder. The male, at least at first, seems 

 to be more wary and cautious in this respect than the female when 

 approaching the nest. 



By the second day the young reach toward the opening of the nest 

 in soliciting food. At 4 days the eyes of the young are slightly open 

 and the edges of the gapes have assumed a more pronounced yellow. 

 The feather papillae in the various feather tracts show prominently. 

 The young are much more active and move themselves about the nest 

 more readily with the aid of their rapidly growing legs. They are 

 also quicker in responding to the parents arriving with food. Ex- 

 crement is voided by turning the rear of the body toward the opening 

 of the nest. During the first day or two the excrement is eaten by the 

 adult birds but as the young become older more and more of it is 

 carried away to be dropped at a considerable distance from the nest. 



