424 PEARL— SEX RATIO IN DOAIESTIC FOWL. 



quainted. If, as may well be the case, he has overlooked some ex- 

 tensive tabulations of sex ratios in birds, he will be very grateful for 

 the pertinent references. 



It is evident enough from these figures that the sex ratio varies 

 in domestic birds quite as extensively as it does among domestic 

 mammals. In general there would appear to be a tendency toward 

 the production of a slight excess of males among two of the sorts of 

 birds here dealt with. This seems certainly true for pigeons. The 

 canary results are not very clear either way. Heape gives data on 

 the sexes from two canary breeders. The results are widely dif- 

 ferent. This difiference in sex ratios Heape attributes to differences 

 in the mode of managing the breeding birds. Here it suffices 

 merely to pToint out that in any case, the numbers on which the 

 canary ratios are based are statistically very small. It may well be 

 doubted whether the deviations exhibited in Heape's material are in 

 reality significant. 



In the fowl the case appears to be different, all available statistics 

 agreeing in showing a normal excess of females. It is, however, the 

 opinion of many poultrymen of long experience, that the usual condi- 

 tion is practical equality of the sexes, with a small but steady pre- 

 ponderance of males — a sort of sex ratio similar to that which man 

 exhibits. The practical equality of the production of the sexes in 

 poultry has been noted by various writers.^ 



But all of the actual statistics which I have been able to find 

 show the slight preponderance to be of females and not of males. 

 The agreement between Darwin's figures and those of the present 

 investigation is nearly perfect. General experience of poultrymen 

 would indicate that the very low sex ratio got by Field could not be 

 considered as normally representative of fowls in general. The 

 close agreement of my figures with Darwin's, collected rather more 

 than a decade later than Field's, would seem definitely to negative 

 the suggestion of the latter that the normal proportion of the sexes 

 in poultry has actually changed since Darwin's time " as a result of 

 the breeders' desire to produce a larger proportion of females." 



9 E. g., Beeck, A., " Die Federviehzucht," Bd. L, Berlin, 1908, p. 563. 

 Lewis, H. R., " Productive Poultry Husbandry," Philadelphia, 1913, p. 250. 



