BELL'S VIREO 257 



of such a lining in all the many references to this species in the 

 literature. 



Eggs. — Bell's vireo lays three to five eggs to a set, but four seems to 

 be the commonest number. Those that I have seen are ovate, or 

 somewhat pointed ovate, and lusterless white, with a few fine dots 

 of dark brown or blackish, scattered mainly about the larger ends. 

 Others have reported spots of lighter brow^n or reddish brown. Some 

 eggs, and apparently some entire sets, are nearly or quite spotless. 

 Rarely, an egg is more heavily spotted. The measurements of 50 

 eggs average 17.4 by 12.6 millimeters; the eggs showing the four ex- 

 tremes measure 18.8 by 12.7, 17.0 by 13.2, 16.5 by 11.9, and 16.8 by 

 11.4 millimeters. 



Young. — All observers seem to agree that incubation normally 

 lasts for about 14 days, and that this duty is shared by both sexes. 

 Pitelka and Koestner (1942) found that "incubation began after 

 laying of the first Qgg and lasted 14 days. Nestling life lasted 11 

 days. * * * Both sexes participated in incubation and care of 

 young." Mrs. Nice (1929) states that in one of her nests there were 

 four eggs on May 15, there having been only one egg on May 12; 

 "three of these hatched May 28, the last. May 29 ; hence, incubation 

 must have started with the third egg and lasted 14 days." Of the 

 feeding of the young, she says : 



The meals were brought at a rnpkl rate, once every 4.9 minutes during five 

 and a half hours of watching. To be sure, some of these T.'j meals, at least five 

 and perhaps a dozen, went into the female's crop, so that the young received 

 food once every five minutes on an average, or three times an hour for each little 

 bird. The male fed 54 times, the female 21. * * * 



In this fragmentary study of the home life of a pair of Bell Vireos, the 

 enthusiasm of the male throughout the cycle was delightful to witness — his 

 intense interest in nest building, his exuberance while incubating, and his 

 devotion to the young both in occasionally brooding them and in assuming the 

 major part of the task of feeding them. * * * The average duration of 

 brooding was 13 minutes on the part of the female and three for the male. Both 

 parents ate the feces the third and fourth days and carried them away after 

 that, the female disposing of seven in the five hours, the male of eight. 



Mr. Du Bois (1940) says that during an "hour and forty-four 

 minutes of watching, the young were fed seven (or possibly eight) 

 times, mainly wath smooth caterpillars ; they were examined on four 

 occasions without being fed, and were twice brooded. * * * Both 

 birds stood at the fork side of the nest, on one branchlet or the other 

 (never on the unsupported edge), to inspect or to feed." He 

 continues : 



The newly hatched young were of a pinkish or reddish color. When one 

 day old they remained entirely naked. Examination through a reading glass 

 disclosed no trace of down or filament on any part of the reddish flesh-colored 

 skin. The lining of the oral cavity was slightly yellowish, without markings. 

 The wings were slender but relatively rather long. 



