THE CYCLE OF LIFE 431 



instincts of the parents and those of the offspring. In- 

 dividual disturbances of the harmony or attunement are 

 continually occurring, and are often misinterpreted as 

 insoluble puzzles. In the cuckoos and cow-birds a remark- 

 able change in instincts has been evolved as a modus 

 vivendi to meet a disturbance of the time-keeping. 



We give a shortened statement of Herrick's analysis of 

 the reproductive cycle. 



1. The spring migration to the breeding area or birth- 

 place. 



2. Courtship and mating, often attended by song and 

 dance, especially in the male. 



3. Nest-building : (a) selecting a site or using an old 

 one ; (6) building the nest or adapting an old one. 



4. Egg-laying, usually at daily intervals in the completed 

 nest. As in (3), this is often attended by instincts of 

 guarding, fighting and concealment. 



5. Incubation or brooding instinct ; attended as before 

 by instincts of guarding, fighting and concealment ; often, 

 as it proceeds, allaying all fear ; including a variety of 

 instinctive acts, sometimes recurrent, as removal of eggs 

 in bill, inspection of eggs, stirring of eggs with bill or feet, 

 cleaning nest by removal of broken eggs or shells, shielding 

 eggs from heat or cold, and sometimes hiding them with 

 covering of wings. 



PARENT. YOUNG. 



6. Care of the young Initial responses at and 

 collecting food ; feeding the after hatching ; swallowing 

 young ; inspecting the nest reflexes ; call notes, and 

 and nestlings ; cleaning later alarm notes ; burrow- 

 both ; etc. ing under old bird ; etc. 



