1602 U.S. NATIONAL MUSEUM BULLETIN 237 paet 3 



size in an eastern population on Southampton Island, where 78 nests 

 held an average of 5.8 eggs and 71 of these clutches, found between 

 June 21 and July 21, contained six eggs. It is of interest that while 

 no seven-egg clutches were observed in Alaska, Watson (1957) and 

 Wynne-Edwards (1952) observed one and two of this size, respectively. 



Wynne-Edwards (1952) presents evidence of a decline in clutch size 

 as the season progresses: "five clutches begun between June 6 and 

 15 numbered 5, 6, 6, 7, 7, and five begun between June 19 and July 2 

 numbered 4, 4, 5, 5, 5. (The probability is about 30 to 1 against the 

 apparent difference being due merely to chance.)" Drury (1961) 

 states: "Early nests (hatching 3-9 July) contained consistently larger 

 clutches (6, 6, 6, 6, 5, 4) than later nests hatching 10-15 July (5, 5, 

 4 } ± } 4 ? 4, 4 ? 3, 3)." Sutton and Parmelee's (1955) data show 11 

 clutches hatching before July 3 averaged 4.7 eggs and ones hatching 

 later averaged 4.3 eggs. 



Egg color and pattern seems to be so generally variable over the 

 range of the species as to merit no special discussion for this race. 

 The measurements of 50 eggs average 20.9 by 15.3 millimeters; the 

 eggs showing the four extremes measure 23.9 by 16.8, 18.8 by 15.8, 

 and 19.4 by 14-2 millimeters. 



Incubation. — Considerable variation exists in the onset of incubation 

 with respect to number of eggs laid, which may be a matter of adjust- 

 ment by individual females to local climatic conditions. If so, it 

 could be construed as an interesting adaptation to arctic conditions. 

 Wynne-Edwards (1952) states that "Incubation begins with the first 

 egg" because, as he elaborated in his discussion of the redpoll, "the 

 temperature in June is below freezing for much of the 24 hours." He 

 found, however, that the actual hatching period in six cases ranged 

 between 2 and 4 days. Watson (1957) found that the females at two 

 nests definitely started to incubate from the laying of the first egg, and 

 early incubation was suspected in most other nests, although in a few 

 it definitely did not occur. At one nest the eggs were cold on many 

 visits during the first two days of laying, but warm after the third 

 day. At another nest the female did not sit for at least all of the two 

 afternoons of the days she laid the first two eggs; here three young 

 hatched the same day followed by the fourth early the next day. A 

 much greater spread in hatching resulted from the early incubation 

 at most nests. At the nest where all 5 eggs hatched, the hatching 

 occupied at least 3 full days, and about 3 days at another nest where 

 5 eggs out of 7 hatched. 



Drury (1961) notes similar variation in the onset of incubation 

 and he discusses it for other populations throughout the range of the 

 species. 



