362 BULLETIN 170, UNITED STATES NATIONAL MUSEUM 



had got a snowy owl's nest with four eggs. It was merely a scrape in 

 the top of just such a little rocky eminence as we had been expecting 

 to find it on, and there were a few feathers half-buried in the lichens 

 and fresh snow close round about the nest" (pi. 79). 



Eggs. — The snowy owl ordinarily lays five to seven or eight eggs, 

 but sometimes as few as three or four, and as many as 13 have been 

 found in a nest. The eggs are like other owls' eggs, but they are often 

 more elongated, to oblong-ovate. The shell is somewhat roughly 

 granulated and without gloss. The color is pure white or creamy 

 white. Bendire (1892) says: "A few corrugated lines starting a trifle 

 beyond the center of the egg and running to the longer axis are notice- 

 able in the majority of specimens examined by me." The measure- 

 ments of 56 eggs average 56.4 by 44.8 millimeters; the eggs showing 

 the four extremes measure 60.5 by 47, 58 by 47.5, and 50.6 by 41.7 

 millimeters. 



Young. — Dr. Pleske (1928) says that "the duration of incubation 

 of the eggs of the Snowy Owl has been determined in the aviary of 

 Fontaine as between 30 and 34, with an average of 33 days." He 

 refers to a set that "was found at Kotelny Island, 24 June 1902, and 

 contained two nestlings and eight eggs. It was collected 6 July 1902, 

 and then consisted of nine nestlings of very different sizes and a single 

 egg, from which the young was on the point of hatching. During this 

 period of twelve days seven young had thus hatched out, which gives 

 us an average of 41 hours between the hatching of each young bird." 



From the foregoing facts he has figured out a table showing the 

 approximate hatching time of each young bird, which shows "that 

 precisely at the moment of hatching of the last young of the set, the 

 first one had reached the age of 356 hours, that is, 15 days and 9 

 hours." He quotes Professor Collett as follows: "As in all birds of 

 prey the Snowy Owl does not lay its eggs one after another at brief in- 

 tervals but over an extended period and at irregular intervals, so that 

 by the time that one egg is laid, incubation will already have begun 

 with those laid earlier. * * * The young one hatched from the 

 first egg should thus be almost completely fledged by the time the last 

 one is hatched. So the young covered with thick down may evidently 

 share in covering the remaining eggs, for the parents are quite busy 

 enough with the care of raising the young which in part are already 

 half grown and require a considerable amount of food." 



Dr. Sutton (1932) says: 



The female alone incubates, while the male defends the nest, and feeds his mate. 

 The period of incubation was found to be about thirty-seven or thirty-eight 

 days. * * * 



The small young are fed on mice and small birds, especially the young of shore- 

 birds, longspurs, and buntings; and at this time of the year the owls probably 

 destroy more small birds than at any other season. 



