yo 'Journal of Comparative Neurology and Psychology. 



and those that occur immediately before each act of copulation. 

 Throughout the greater part of the day, the male frequently gives the 

 bowing-coo, the nest-call, or the perch-coo, the female gives the nest- 

 call, and both birds kah frequently and loudly. Preening of the 

 feathers in a spasmodic manner, especially the preening of the wing 

 on the inner side, and the preening of the head of the mate as the 

 two birds sit side by side, are equally characteristic activities of the 

 day. Immediately before copulation there is usually a special cooing 

 and a special show of eros by preening inside the wing, and there 

 is invariably the act of billing, the female putting her bill into the 

 mouth of the male, and he disgorging a little of the contents of his 

 crop for her to take. This is the signal, as it were, Avhich is imme- 

 diately followed by copulation. 



The search for a nesting-site and the building of a nest, which have 

 been going on at the same time with the operations already described, 

 are accompanied by a great deal of vocal performance, especially 

 nest-calling. Both birds engage in the search for a nesting-site. 

 When either bird has found a likely place, it sits there and nest-calls 

 by the hour. The mate, hearing this call, is drawn to the spot, and 

 then both sit together and nest-call, gently flip their wings, and 

 preen each other's heads for a long period. The construction of 

 the nest is carried on by one bird, usually the female, sitting in the 

 nest and building in the materials which are brought by its mate. 

 Each time the male brings a straw the female receives it with the 

 gentle flip of the wings and the nest-call. 



When the eggs have been laid, the male and the female take turns 

 most regularly in sitting on them. This fact gives to the daily 

 program during incubation a complexity and definiteness which are 

 not equalled at any other time in the dove's life. The present point 

 in the life-history is therefore a good place at whj<^h to insert a de- 

 scription of the daily cycle. 



D. The Daily Cycle. 



The daily cycle of activities reaches its maximum complexity 

 and its greatest definiteness at the time of incubation. At any other 

 time it is indeed noticeable that the birds follow a daily program : 



