66 Bergtold, A Study of the House Finch. [fan. 



This table of weights is of considerable interest, and, it is hoped, 

 also of value as establishing, with these eight nestlings, a pro- 

 visional curve of weights for growing House Finches. It will be 

 seen that the least weight, at hatching, was 30 grains, and the 

 greatest 63 grains. This wide variation may be explained on the 

 assumption that the high weight was partly due to this nestling's 

 having been fed by the old birds prior to the weighing. If we 

 assume that the egg is hatched at night, which seems always to have 

 been the case in the writer's experience, it is probable that the 

 incubating female fed the young bird during the night, or shortly 

 after dawn, both periods being before the writer took the daily 

 weights (viz., S a. m. each day) and one or two feedings will materi- 

 ally increase a very young nestling's weight. 



The average initial weight of eight nestlings was 42 grains, and 

 the average last weight (before flight) was 262 grains. If taken by 

 broods this last average was 249 grains, and 275 grains (disregard- 

 ing fractions), extremes Avhich show considerable divergence, a 

 difference which might almost be predicted a priori, when one recalls 

 the marked difference existing between pairs of parent birds in 

 their attention to the young. A number of other young birds have 

 been weighed, these young House Finches having been caught 

 about the writer's premises, and in neighboring yards, and identi- 

 fied as not being from nests Nos. 4 and 5. Of these young birds, 

 two were from a nest which was attended by two old birds noticeably 

 careless in their attentions to the young. It was apparent for days 

 that they paid unusually infrequent visits to the nest; the two 

 nestlings in it, on the last weighing, were found to be far below the 

 average, one standing at 181 grains, and the other at 209 grains. 

 Including these two obviously under weights, the average weight, 

 determined from eleven birds able to leave the nest (not in- 

 cluding birds from nests Nos. 4 and 5) was 250 grains. Excluding 

 the manifestly underweight nestlings, the average of the remaining 

 nine was 262, an interesting correspondence to the similar weight 

 averaged from the nestlings of nests Nos. 4 and 5. The weights 

 from nests 4 and 5 show that a House Finch will grow to within 

 02' , i or more) of the adult weight before it is three weeks old, 

 which, is a surprisingly rapid growth. The extremely low weight 

 (1S1 grains) exhibited by one nestling able to leave the nest proves 



