408 BULLETIN" 179, UNITED STATES NATIONAL MUSEUM 



taining 5 eggs, was taken on June 10, 1932. Nests examined later 

 in the season were of a similar structure but in general were lined 

 with many more fluffy feathers. A nest found by Knight (1908) 

 on June 16, 1900, at Veazie, Maine, was composed of dried grass and 

 lined with white feathers. It contained five eggs and was located 

 in a burrow 3 feet deep. The entrance opening was 3 inches in 

 diameter, and the nest chamber was 5 inches across. Stoner (1936b) 

 says: 



The type of material used depends more or less upon what is available in 

 the near vicinity. If a freshly movpn hayfield is at hand, grass stalks will 

 be gathered from this source, both green and dried blades being acceptable. 

 Long thin blades or stems to be preferred. If a farmyard is near, a consid- 

 erable amount of straw is likely to be found in the nest. Weed stalks are 

 also used and some of these are of surprising length and size for so small 

 a bird to manage within the limited confines of the burrovp. For example, a 

 dried grass stem 25^2 inches long was found in a burrow. * * * Rootlets, 

 horse hair and pledgets of sheep's wool often form a part of the nest. Some 

 nests, however, are composed almost entirely of blades of grass. In July, 

 particularly, the dried, black rootlets of the field horsetail, which dangle 

 from the sandy banks in so many places along Fish Creek, frequently comprise 

 a large part of the nest material. 



The first eggs, and sometimes all in the clutch, are usually layed 

 in the unlined nest. However, as egg-laying and incubation pro- 

 ceed, feathers are added as a lining, so that by hatching time a warm 

 cozy bed awaits the young. 



Eggs. — The eggs are pure white, but Stoner noted a departure 

 of this coloration in which two of a set of five eggs that he found 

 May 27, 1931, had numerous, minute, rounded elongate or irregular 

 brownish marks. In about 50 nests examined in the vicinity of 

 Brunswick, Maine, four and five eggs constituted the complete set 

 in the large majority of cases. Only one set of six eggs was found, 

 but sets of six have been frequently reported from other localities. 

 Sets as large as seven (Knight, 1908) and even eight eggs (Forbush, 

 1929) have been reported, but these larger sets are very rare. 



The measurements of 50 eggs average 17.9 by 12.7 millimeters; the 

 eggs showing the four extremes measure 19.8 by 12.7, 19.3 by 13.7, 

 15.2 by 11.4, and 15.7 by 10.7 millimeters. 



Young. — Both male and female take part in the incubation of 

 the eggs and the brooding of the young. Stoner definitely ascer- 

 tained this fact by determining the sex by dissection. The period 

 of incubation varies somewhat, depending on a number of controlling 

 factors. In studies made by Stoner it was determined to be about 

 14 to 16 days, counting from the date on which the last egg was laid 

 to that of the first hatching. The following account of the young 

 is taken from Stoner's (1936b) exhaustive studies of the bank swallow. 



