158 BULLETIN 17 9, UNITED STATES NATIONAL MUSEUM 



Contrary to Mr. Jewett's experience, George Oberlander (1939) 

 mentions the building of two nests entirely by the females, successive 

 mates of the same male. 



Several instances have been reported in which newly built black 

 phoebes' nests have been used by other birds. Wilson C. Hanna 

 (1933) found two nests that had apparently been seized by house 

 finches {Carpodacus mexicanus frontalis) in spite of the presence of 

 the rightful owners, while Harold M. Holland (1923) describes the 

 joint use and alternate occupancy of a nest by phoebes and house 

 finches. This latter nest was later found to have been deserted by 

 both, though containing six eggs of the phoebe and five of the finch. 

 Emerson A. Stoner (1938) reports finding a nest containing three 

 phoebe's eggs below, then a scanty lining of fine hairs, and above 

 that an egg of the dwarf cowbird {Molothrus ater obscunts) and 

 three of the western flycatcher {Empidonax diificilis). 



Eggs. — Mr. Tyler (1913) remarks that "it is interesting to note 

 that when four eggs constitute a set there are generally three that 

 are unmarked and one that is quite heavily spotted with red dots 

 on the larger end but when there are five in the set the additional 

 egg nearly always has just a few very fine spots like dust. My ob- 

 servations show that nearly always the spotted egg is the last one 

 to be deposited. If that is the rule, then should a set of seven or 

 eight eggs happen to be laid we might expect one or two specimens 

 as heavily spotted as a kingbird's egg." 



The measurements of 60 eggs average 18.7 by 14.4 millimeters; 

 the eggs showing the four extremes measure 20.3 by 15.2, 17.3 by 14.2, 

 and 17.8 by 13.2 millimeters. 



Young. — The incubation period for two sets of five eggs each has 

 been recorded by Mr. Oberlander (1939), counting in each case from 

 the laying of the last Qgg. In one nest three eggs were hatched, the 

 first after 17 days, the others on the following day; in the second 

 case, three eggs were hatched on the fifteenth day and another the 

 next day. In this second nest, the four nestlings remained about 21 

 days, which in the light of the following account indicates consider- 

 able variability in the length of this period. 



Mr. Jewett (1899) states that the young "remained in the nest 

 on an average about two weeks, or until it was too small for them," 

 and that "three broods were generally reared in each year, the first 

 and second usually consisting of five, and the last of four birds. The 

 youngsters never remained long after they had been turned adrift, 

 usually disappearing on the third day " Eegarding the condition 

 and care of the young, Mrs. Irene Grosvenor Wheelock (1904) says: 



For some unexplained reason the nest of this species, like that of Say phoebe 

 and the Eastern phoebe, is infested with innumerable insects, which frequently 

 cause the death of the young. This seems strange in the case of birds that 



