OLD CROW 237 



sets of eggs collected, and from three broods of birds near fledging 

 which were banded ( see fig. 19 ) . The degree of incubation or progress 

 toward fledging was estimated by considering 9 days the duration 

 of nestling growth, following Barbara Oakeson's (1954) studies on 

 Gambel's sparrows at Mountain Village, Alaska, and our observa- 

 tions at Anatuvuk (L. Irving and Krog, 1956), and 12 days the 

 duration of incubation. In six nests the first egg was calculated 

 to have been laid between May 25 and May 28. The first egg was 

 laid 11 days after the first male was seen and the interval between 

 the arrival of the first male and the average date for the first egg 

 in six clutches was 13 days. The schedule appears reliable because 

 there is no error in calculating the date of the first egg from the dis- 

 covery of ruptured ovarian follicles and a well formed egg. As addi- 

 tional evidence for early laying, an egg 7 mm. long was found in the 

 first female collected on May 21. This egg could be expected to 

 be laid within a few days. 



At Anaktuvuk, two eggs were recorded by Simon Paneak as found 

 on June 1, 1954, and two. females, taken on May 25 and May 27, 

 each contained an egg 3 mm. long. The first migrants are usually 

 seen there about May 15. This suggested an interval of about 15 

 days between the first arrival and the first egg, three days shorter 

 than was estimated from occasional earlier records at Anaktuvuk. 



The careful records of the schedules of individual Gambel's spar- 

 rows at Mountain Village presented by Barbara Oakeson (1954) 

 showed that in 1950 the first male arrival on May 10 was followed 

 by the first egg on May 25, an interval of 15 days. At Old Crow the 

 completion of all of the preparations for the first laying observed oc- 

 curred in the 11 days after the first male bird was seen. There the 

 country is evidently well suited for the large breeding population, 

 while at Mountain Village, Barbara Oakeson found Gambel's spar- 

 rows not numerous, and at Anaktuvuk they were far less common than 

 at Old Crow. Mrs. Oakeson found that the duration of the intervals 

 between arrival and laying at Mountain Village was only about half 

 as long as for Z. I. pugetensis at Friday Harbor. There is undoubtedly 

 acceleration of the breeding cycle at Old Crow and shortening of 

 its duration by synchronization of the schedule throughout the popu- 

 lation. The shortening of the schedule is of course a necessity in a 

 high latitude where the season suitable for breeding is so short. From 

 information which Mrs. Oakeson kindly provided on the breeding of 

 Gambel's sparrows at College, Alaska, in 1957, the interval between 

 the average first arrival of males and first egg was 13 days and only 

 4 days after the average date of arrival of the females. 



Her studies will indicate whether or not there is acceleration in the 

 physiological processes preparatory to breeding. We do not have that 



