72 'Journal of Comparative Neurology and Psychology. 



gave a similar series of four coos. After that she often fluttered her 

 wings when the male happened near the nest, but she never cooed. 

 The male's 487 coos were pretty evenly distributed over the whole 

 time. But they began at the hour of dawn with a somewhat slower 

 rate than the average, rose to a maximum just after the bird had 

 left his roost and breakfasted, and then declined somewhat until the 

 time of taking the nest. 



The male takes the nest at 8.30 A. M. and keeps it until 4.45 P. M., 

 when he yields it again to the female, who sits steadily until 8.30 

 the next morning. Of course the birds are not punctual to a single 

 minute, but their regularity during early incubation, if nothing 

 occurs to disturb them, is remarkable. Towards the close of incu- 

 bation, and after hatching, they are much less regular. And at any 

 time, the presence of other birds or of alarming objects is likely to 

 throw them out of the regular order. Thus on the 2d of July which 

 I have been describing, the female left the nest at 8.15 A. M., being 

 alarmed by the barking of a dog, and the male entered the empty 

 nest at 8.19, which was probably a few minutes earlier than he would 

 otherwise have done. The most potent disturbing factor, however, 

 is the presence of other birds, which arouses the jealousy of the male. 



Changing places on the nest. — ^^Vhen the male comes, at his due 

 time, to relieve the sitting female, or when the female comes similarly 

 to relieve the sitting male, there is always a little communication or 

 ceremony. There is little difference in behavior between the male 

 and the female on this occasion. There is much variation in the 

 ceremony, but the usual procedure is about as follows. The bird 

 that is out, comes to the nest, giving the kah as it arrives ; it jumps 

 on the edge of the nest-box, kahs again, flips its wings and tickles the 

 head of its sitting mate. The sitting bird responds by fluttering 

 its wings and showing evident satisfaction with its mate's attention. 

 This exchange of greeting is usually sufficient; after a few caresses, 

 and sometimes cooings, on the part of each bird, the sitting bird 

 gently rises and steps forward, and the other steps in behind and 

 settles upon the eggs. It sometimes happens that the sitting bird 

 leaves before the other comes, as in the case mentioned above when 

 the sound of a dog's bark caused the female to leave a little before 



