236 U. S. NATIONAL MUSEUM BULLETIN 217 



Gambel's white-crowned sparrows were recorded as first seen at 

 Old Crow on May 14. By May 17 many were singing. On May 19 

 the numbers had further increased until they were the most commonly 

 seen bird in the vicinity of the village. At this date they appeared 

 to have settled most territorial limits, in which the males were sing- 

 ing, but there were still some territorial adjustments in progress 

 through invasion and judgment by combat. 



In average weight of males and females white-crowned sparrows 

 at Old Crow did not differ significantly from males and females at 

 Anaktuvuk, or from males at Mountain Village, Alaska (Oakeson, 

 1953). The average weight of six males in the first 5 days after 

 arrival was greater than the average of nine males weighed during 

 the next 30 days, and the degree of fatness recorded indicated that 

 some fat which was present at the end of migration had been con- 

 sumed at the time when the young were fledged (see fig. 19, in the 

 Appendix) . 



During the time of laying eggs three females weighed 31, 33, and 

 31 grams, about 8 grams, or over 30 percent above the average weight 

 of nongravid females. The heaviest, which had laid five eggs, as 

 shown by collapsed ovarian follicles, and contained a formed egg, was 

 then nearly 10 grams heavier than the usual nonbreeding female. An 

 individual egg might weigh three or four grams, but this is not enough 

 to account for the excess in weight of the gravid females. One of these 

 females was marked as having little fat and two as medium fat. The 

 degree of fatness was not greater than in nongravid females, so that 

 not all of the tissues responsible for the increment in weight can be 

 indicated. 



The efficiency of a hen in converting food to egg may be 77 percent 

 (Brody, 1945), so that in forming its own weight of eggs, as is con- 

 tained in a clutch of six, a sparrow must consume more than its own 

 equivalent of food for egg production during the six days of laying. 

 The rate of energy consumption in forming eggs probably requires 

 something like twice the usual consumption of food by the female 

 bird during laying. Evidently the resources in the sparrow's meta- 

 bolic capability and its food supply in arctic spring are sufficient 

 to permit this sudden extra metabolic effort required during egg 

 laying. I have earlier remarked that while male birds of several 

 species appear to decline in weight and fatness after arrival in arctic 

 Alaska and during breeding, females do not so often show a decline 

 until after the young birds are being fed. The good condition of the 

 laying birds is evidence that these events impose no stress. 



The reproductive schedule of Gambel's sparrows at Old Crow can 

 be indicated from the ruptured ovarian follicles found in two female 

 specimens, each of which also contained a formed egg, from three 



