EFFECT OF SEASON OF HATCHING UPON DISTRIBUTION OF FERTILITY. 59 



laid 15 clutches of eggs, with 1 egg only in a clutch! She has never laid a clutch 

 of 2 eggs, and no other known member of her species has a comparable history. 

 The fourth female (489) was not veiy thoroughly tested. During her 20 months 

 of life she laid no eggs, or onl}^ one at most, and was thus certainly less fecund than 

 the 3 females which had preceded her. The fifth female (429) when well tested 

 showed, both with orientalis and with alba, a very low percentage of fertility, the 

 percentage, too, being higher with the former than with the latter. The sixth, 

 seventh, eighth, and ninth females, the last of the j^ear, all had sufficient oppor- 

 tunities to mate without doing so. The length of life of these birds was less than 

 that of birds from the first of the season, but females 500 and 433 (first and third 

 of the season) had each produced manj^ young before they had reached the shortest 

 of the shorter life-terms of these end-of-the-season females. 



For a closer and more critical view of this situation the series of tables and the 

 summarized complete individual histories which follow may be consulted. Many 

 questions will arise, the answer to which can be found in definite dates and details 

 presented there. 



FERTILITY OF FEMALES OF THE SERIES. 



The females of the series will be considered first. It has already been pointed 

 out that the most fertile member of this family was female No. 500, which is at the 

 same time the first or earliest of the females of the list. On April 13, 1912, this 

 bird laid her first eggs (only 10 months old) before her removal from her wdnter 

 quarters with other T. orientalis. On April 24, 1912, she was placed with a St. alba 

 that proved to be a female; they seem to have mated and each soon laid (4) eggs. 

 Neither of these first eggs had opportunity to be fertilized. These and several 

 others from the series of 1912 and 1913 were used for other studies. Late in May 

 of her first breeding season she was given a male St. alba ; from this pair 21 additional 

 eggs were obtained during the season. The fertilitj' of 15 of these was tested. 

 The fourth, fourteenth, and sixteenth of the series were infertile. 12 young hatched 

 and practically all are alive at the end of 3 years (table 43). 



During 1913 the same pair produced 28 eggs and 15 young, 3 eggs again testing 

 infertile. Her mate died of tuberculosis November 24, 1913. A new *S^ alba 

 (nearly pure) mate was given April 1914. From this pair (till March 20, 1915) 

 50 eggs have been obtained. All except 4 broken ones have been tested; 2 of these 

 broken ones are known to have contained live embryos, and 2 showed no develop- 

 ment whatever. These latter were the tw^enty-first and twenty-third eggs of the 

 season (August 7 and August 22). Two full-term embryos died from faulty incu- 

 bation, and 1 egg showed only a trace of development. Nearly all of the young 

 of 1913 and 1914 are also still alive (tables 43 and 44) at the time this is written. 

 It is clear, therefore, that this female — the first female of the season — ^^vas by far 

 the most fertile of the entire family to which she belonged. Her very long breeding 

 record is placed in the following chapter because of its bearing on subjects discussed 

 there. 



The short earlier statement, together with table 29, supply all that it is neces- 

 sary to present concerning No. 481, the second female of the season. Likewise 

 the very full treatment accorded in the preceding chapter to the offspring of the 

 third female (No. 433) sufficiently presents the degree of fertility of this bird. 

 It was there noted (table 20) that even with a weakened "mutant" inbred male 



