\ dI. XXX 

 1913 



Bbrotold, .1 Study of tin House Finch. 67 



thai a young l>inl attaining but 62% of its normal weight can shift 

 for itself, or can, at least, try to do so. On the other hand, one 

 nestling in "nest 5-C-07" reached within thirteen days after 

 hatching 99 % of the adult weight (viz., 289 grains: 2S6 grains). 

 Brood "4-B-07" shows ns that a bird may be hatched two days 

 before another and yet weigh when leaving the nest but 3% more 

 than docs the latter, an observation which seems to point to the 

 fact that various members of a brood follow very closely a certain 

 level of growth and this level of growth is also shown by the 

 weights of each bird in relation to the weights of the others, when 

 all left the nest. 



There is, however, a noticable difference in the "flight weights" 

 of the members of brood "5-C-07," though it appears small when 

 expressed in percentages, i. c, 6 % between the heaviest and lightest 

 (280:268). It is to be noted that this difference occurred in the 

 birds of brood "5-C-07" notwithstanding that all four birds were 

 hatched within twenty-four hours; and the weights of the various 

 eggs in this nest were too close to each other to presuppose a 

 better start for any given ovum because of greater egg weight. 



Toward the close of nest life some birds lose in weight, which 

 may be, and probably is, due to the parents' slacking up on feeding, 

 in their efforts to coax the nestlings to fly. A loss in weight may 

 be due, in some instances, to an alvine discharge having occurred 

 just before the bird was weighed, an incident noted several times 

 during this study. Such a discharge may amount to 5 grains, 

 actual weight. 



The following percent gain curve shows, as one would expect, a 

 very large percentage gain in weight during the first days of nest 

 life, the gain then going on a diminuendo scale to zero, or even to a 

 loss. It is surprising to learn that a nestling may gain 60 % in 

 weight in twenty-four hours. 



A singular feature shown by the percent gain curve is the spurt 

 upward shown on the fourth day, the mean of the eight birds in 

 broods "4-B-07" and "o-C-07" showing this spurt unmistakably. 

 It is highly possible that this peculiarity in the weight gain would 

 not obtain in a large series of weighing. The writer was unable to 

 determine whether a larger egg gives its embryo a better start than 

 does a small egg its embryo. The weights of these eight nestlings 



