1496 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 3 



brown," "russet," "cinnamon brown," or "Brussels brown." Some 

 eggs have undermarkings of "pale neutral grey." The spottings 

 generally are more or less evenly distributed over the entire surface, 

 sometimes obscuring the ground color and making it appear to be a 

 light buffy brown. They vary considerably both in shape, size, and 

 intensity. The measurements of 400 eggs average 20.4 by 15.6 

 millimeters; the eggs showing the four extremes measure 25.9 by 

 17.8, 24.5 by 18.3, 16.9 by 15.4, and 19.6 by 12.8 millimeters. 



Turning to the race melodia, the measurements of 50 eggs average 

 19.5 by 15.1 millimeters; the eggs showing the four extremes measure 

 21.9 by 14.5, 20.1 by 16.8, 17.8 by 14.2, and 18.0 by l/ h millimeters. 



Incubation. — Forbush (1929) states that incubation is "by both 

 sexes, female chiefly" and that "some males assist the females a 

 little * * *." However, there is no evidence that males have an 

 incubation patch, without which they would be ill-equipped to supply 

 heat to the eggs. Mrs. Nice (1937) found males of the race euphonia 

 lack this patch, and her unequivocal statement that only the female 

 euphonia incubates casts doubt on Forbush's contention. The role 

 of the male during incubation is probably confined to the defense of 

 territory and nest. 



Incubation seems to start sometime not many hours from the 

 laying of the last egg of the set, if this inference may be drawn from 

 the failure of observers to report differences in development in the 

 young of a brood. In euphonia Mrs. Nice observed that most often 

 a clutch hatched over a 2-day span, indicating that incubation had 

 begun before all eggs were laid. 



The incubation period is said by Knight and Forbush to be from 

 10 to 14 days, but it is doubtful if accurate measurements of the 

 period, as it is presently defined, would be less than 12 days, as in 

 euphonia (Nice, 1937). W. E. Schantz (1937) watched a female 

 euphonia incubate three eggs (laid July 10-12) for 24 days; the eggs 

 failed to hatch. 



Young. — Most of our knowledge of the development of the behavior 

 of nestling song sparrows comes from Mrs. Nice's work, devoted 

 chiefly to euphonia. The following paragraph is based on her report 

 (1943). The development of the plumage is described below under 

 the heading Plumage. 



Newly hatched song sparrows can grasp, gape, swallow, defecate, 

 and change location "by means of uncoordinated wrigglings." A 

 feeding note has been heard in 2-day-old birds. The eyes begin to 

 open at age 3 or 4 days. Incipient preening motions appear at age 

 5 days, as do, rarely, cowering and the ability to utter a location 

 call. At age 7 days many motor coordinations are acquired, and 

 henceforth the bird "is capable of leaving the nest." Among the 



