244 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



Young. — Young bluebirds are fed and cared for by both parents 

 more or less equally, but with considera ble variation between different 

 males. For instance, Mr. Smith (1937) says: 



The male of No. 1 pair was not seen to feed the young. * * * The male of 

 No. 2 pair, on the other hand, was particularly active and during some of the 

 observation periods fed the young more often than the female did. The brooding 

 of this pair was carried on exclusively by the female so far as we could learn. 

 [During one hour, from 2.09 to 3.09 P. m.] the male brought food at 2.34:30, 2.37, 

 2.45, and 2.58:30. Total feedings for the interval were nine, five by female and 

 four by male, and brooding lasted twenty-seven and a half minutes divided into 

 five separate periods. This may be compared with an hour's observation five 

 days later, the period extending from 2.54 to 3.54 p. m. Nine feedings occurred 

 within this interval also, but six were by male and three by female and the brood- 

 ing occupied twenty-nine and a half minutes divided into two separate inter- 

 vals. * * * 



In general the period passed by the young in the nest was eighteen days, one 

 exception occurred in the case of No. 2 pair in 1933, when the first brood of four 

 left the nest after seventeen days. 



A brood watched by Mr. Du Bois (MS.) were in the nest just 15 

 days. And Ora W. Knight (1908) says: "The parents take turns in 

 incubating and the eggs hatch in twelve days, the young leaving in 

 fifteen days after they are hatched. Both parents feed them and 

 carefully take away in their bills all the excrement voided by the 

 young." Mrs. Laskey (1939) states that "the only Nashville record 

 of a brooding male Bluebird is that of Simpson in April and May of 

 1937 when one individual was captured twice in a mail box on a nest 

 containing eggs." 



Mr. Smith's (1937) studies of the development of young bluebirds 

 show that on the first day they varied in length from 31 to 41 milli- 

 meters; and that at the time of leaving, the 17th or 18th day, they 

 measured 125 to 130 millimeters in length. "The eyes usually began 

 to open on the 4th day, but in one instance this was delayed until 

 the seventh day. Completion of the process required from three to 

 five days. Tail-feathers appeared on the 8th day. Primaries became 

 noticeable on the 4th day." 



Mrs. Laskey (MS.) gives the following information on the success of 

 hatching and rearing of the young, based on her study for seven 

 years: "A careful analysis of the Desting data, accumulated through 

 regular visits to the boxes, indicates that only 1,569 eggs of the 3,512 

 laid have been successful to the point of survival of the young to the 

 age of 16-17 days when they normally fly from the nest. This is 

 44.67 percent of the total number laid and corresponds to percentages 

 for birds building open nests. It is markedly lower than for hole- 

 nesting species." Mr. Low's (1934) record for efficiency was decidedly 

 better, varying from 62.7 to 87.5 percent. 



Mr. Du Bois (MS.) gives the following account of young bluebirds 



