EASTERN VESPER SPARROW 873 



mean clutch size was 3.7 eggs. He adds that there is "a distinct 

 seasonal decline in clutch size: most of the clutches produced in 

 May contain 4 eggs, most of those produced in late June and July 

 contain 3." There are exceptions, however, and I have found July 

 nests with four eggs, both in southern Michigan and in Oscoda County ; 

 Douglas S. Middleton found a nest with four eggs on July 12, 1947 

 (Oakland County, Mich.) ; G. M. Sutton found a nest at the Edwdn 

 S. George Reserve in which three of the four eggs hatched on July 24, 

 1942; and Lawrence H. Walkinshaw found a nest with five eggs on 

 July 15, 1945. Mr. Bent (MS.) mentioned two nests, each with four 

 eggs, found in Massachusetts on July 1, 1886 and July 9, 1887. 



Young. — The incubation period is reported by John L. George 

 (MS.), Francis C. Evans (MS.), and L. H. Walkinshaw (MS.) to vary 

 between 12 and 13 days; some authors have given the period as 11 to 

 13 days. Incubation is performed chiefly by the female, but E. H. 

 Forbush (1929) comments that both sexes "have been seen on the 

 nest," and Evans has recorded fom* instances in which the male w^as 

 flushed from a nest containing eggs. Both adults have been observed 

 to eat the egg shells. E. M. and W. A. Perry (1918) watched one 

 parent "take a shell some few feet aw^ay from the nest before eating it." 



The female usually and the male occasionally brood the young. 

 The amount of time the young are brooded depends in part on the 

 time of the year, that is, they are brooded more in early May than in 

 June and July. Dming hot summer days the young also are shielded 

 from the sun, usually by the female. Both adults feed the nestlings 

 and both eat or carry away the fecal sacs. 



As with many ground nesting passerines, the nestling period varies 

 considerably from nest to nest. John L. George (MS.) found that in 

 two vesper sparrow nests "the young fledged 9 days after hatching; in 

 a tliird, 10 days; in a fourth, 13 days; and in a fifth, 14 days." If they 

 are disturbed — by banding, weighing, or by a predator — the young 

 will leave the nest at 7 or 8 days of age. Francis C. Evans found the 

 nesthng period to vary from 7 to 12 days, and found the mean period 

 to be 9.1 days. The young are unable to maintain flight when they 

 leave the nest, but they are very quick and agile in moving through 

 the vegetation. Once the young have left the nest, they remain 

 quietly hidden, except when being fed, and they are extremely difficult 

 to find. 



The male apparently takes over most of the feeding of the first 

 brood while the female begins a second nest. The fledglings appear 

 to be semi-dependent on the adults until about 30 to 35 days of age. 

 Evans found adults feeding banded young "which had left the nest 

 18 to 22 days previously." 



