240 U. S. NATIONAL MUSEUM BULLETIN 217 



6-day interval between first observed arrival of fox sparrows at Old 

 Crow and their first egg was even shorter than for Gambel's sparrows. 



It was earlier remarked that the community of fox sparrows was 

 in good order by May 20, for territorial transgressions were not then 

 frequent, although some nests were not a hundred feet apart. Within 

 about 8 days the entire society of fox sparrows had become changed 

 from an organization of individuals in which the influence of sex 

 was scarcely visible to a new social order in which sex impulses were 

 dominant in separating the society into pairs. The social reorgani- 

 zation was mainly effected by the demonstrative activities of male 

 birds. 



The swift settlement of large numbers of fox sparrow in their re- 

 spective territories proceeded so rapidly and, in spite of the brief 

 period of combat, with so little disorder that provision for the social 

 processes which could organize them into a community of families 

 must have been already inherent in the individuals when they reached 

 Old Crow. The expression of social organization appeared only in 

 the nesting environment, but the physiological preparations had been 

 completed and the inclination of every bird toward the correct se- 

 quence of social behavior must have been already perfected. Some 

 common bond, as well as temporal and spatial association, must have 

 joined the birds during their migration toward Old Crow, producing 

 a synchrony in their physiological and social states. Somewhere in 

 each bird's "memory" there is brought about the synchronous prepa- 

 ration of breeding activity which eventually segregates and orders a 

 predetermined segment of the whole migrating population to proceed 

 to settlement on its nesting ground at Old Crow. The social "memory" 

 cannot be described by analytical reference to physiological processes 

 and mechanisms alone, for the organization of societies also involves 

 the environmental terms of time and space that are so evident in the 

 annual migrations of birds. 



In specimens taken of arriving male fox sparrows the testes were 

 not found at their largest size until about May 27, but some must have 

 been ready for breeding before May 20. The early males were mostly 

 medium fat, and examples during early nesting had little fat, but 

 picked up fat again while nestling birds were being cared for. Their 

 generally good condition attests the adequacy of the food supply and 

 suggests that the revolutionary physiological and social transitions 

 while nesting were effected without nutritional strain. 



As was remarked about female white-crowned sparrows, several 

 female fox sparrows preparing to lay were about 8 grams, or 20 per- 

 cent, heavier than the average of nongravid females. This increase is 

 near four times the probability of normal variation in weight of 

 males, and is about twice the weight of an egg. As those individuals 

 were fat, its accumulation and the ovarian enlargement are plausible 



