306 U. S. NATIONAL MUSEUM BULLETIN 217 



leucophrys fugetensis) at Friday Harbor, Washington, on the average 

 went through the same phases of the reproductive cycle about as 

 rapidly as the Alaskan birds. The individuals of the Puget Sound 

 race, however, were not so well concerted in phase of the reproductive 

 cycle as were the Alaskan birds. 



At Barrow, Pitelka (1954) found that 80 to 90 percent of all 

 breeding Alaska longspurs and snow buntings began laying within 

 a single week in the first half of June. These birds pass Anaktuvuk 

 in a relatively prolonged migration extending, respectively, over 

 about 30 and 60 days. Both longspurs and snow buntings winter in 

 quite diverse areas, but at Barrow their reproductive activity is 

 synchronized to occur within a remarkably short time. 



The simultaneous breeding of arctic populations is based upon 

 synchronization of the internal reproductive condition of individual 

 birds. As Mrs. Oakeson (1954) observed, individual arctic birds may 

 take a nesting area, mate, and copulate a little more quickly than in 

 a warmer climate. The sequence is a little expedited, but I suspect 

 that the shortening is produced by reduction in the time required for 

 transition from the end of one physiological phase to the beginning 

 of another. 



At Old Crow, in Yukon, our observations were carried on through 

 only one season and the records in table 14 show the date between the 

 first individual seen of the species and the first egg observed. This 

 information is empirically determined, while the interval between 

 middle of arrival of the species and the middle of laying at Anaktuvuk 

 includes a factor of judgement estimated from a number of years' 

 observations. The species reported upon at Old Crow also differed, 

 including only 5 of those at Anaktuvuk. The average of the intervals 

 observed among 27 species at Old Crow was IT days between first 

 arrival and first Qgg, whereas among 25 species at Anaktuvuk it was 

 14 days, indicating that the progress from migratory to laying con- 

 dition was at similar rates in these two arctic localities. 



In each locality the progress toward laying varied among the 

 species. The longest interval at Old Crow was 31 days and at Anak- 

 tuvuk 34 days. The shortest observed interval at Old Crow was 7 

 days for the fox sparrow, and at Anaktuvuk 4 days for the pintail 

 and arctic tern, a period which seems likely to be too short. At both 

 places the progress of some species from migration to laying was 

 remarkably rapid and of others comparatively leisurely. The species 

 likewise differed in the rapidity of their transition from migration 

 to reproduction. 



It is apparent that the speed of the transition varies among species 

 of ducks at Anaktuvuk and within the family of sandpipers in both 

 localities. Only in the family Fringillidae are the species much 



