INTRODUCTION.

This bulletin is a continuation of the work outlined in Bulletin 117, and partially carried out in Bulletin 118. It contains the original data and summaries and a statistical analysis of the first year egg laying records, as secured through the use of the trap nest, of all Plymouth Rock pullets completing a full year's laying record in the first nine International Egg Laying Contests at Storrs from 1911 through 1919. It differs slightly in its treatment of the records from the two previous bulletins in the series. In each of them, the various color varieties of the breed under consideration were grouped together for analysis. Each of the breeds studied consisted chiefly of a single variety, with a smaller number of fowls in a few closely related varieties distinguished by color. Thus of the Wyandottes the great majority were white, and of the Rhode Island Reds only about three per cent belonged to the single subvariety of this breed, the Rhode Island white. Completeness of reporting and larger numbers were secured by disregarding the distinctions between varieties and including all fowls as members of a single breed type based on conformation and (presumably) common descent. With the Plymouth Rocks the case is somewhat different. The original Barred variety of this breed has given rise to several important color varieties which have come to rival the parent variety in popularity. Consequently the Plymouth Rocks submitted to the contests have been more equally distributed among the various color varieties than any of the other breeds. In the years considered the numbers of the several varieties submitted have been as follows:

There is some doubt as to the relationships between these varieties. It is probable that they are not as closely related as the color varieties of, for example, the Leghorn breed, since some of them have probably not arisen directly from the parent variety, but have been produced by crossing and thereafter bred to the standards laid down for Plymouth Rocks. These considerations added to the fact that it was necessary for other purposes to analyse the records of the Barred Plymouth Rocks separately have led us to choose that variety as the most numerous, and truest example of the breed, for this study of fecundity in Plymouth Rocks. In order that the summary may be complete, however, we have added the most important data for the other varieties without subjecting it to the detailed analysis which the Barred Rock data have received.

SOURCE OF THE MATERIAL.

In the nine years, 1911 to 1919, 790 Barred Rocks were submitted to the contests. The number and location of the breeders or poultry yards which entered these fowls were as follows:

OF THE DOMESTIC FOWL

The geographical sources of this group of Barred Rocks were very diverse and the number of breeders involved was comparatively large. These facts make it seem probable that a representative sample of the breed was secured.

The following table shows the number of pens (1) submitted by each breeder:

More than half of the breeders competed in only one contest, while only ten competed in three or more contests. It is probably only among the fowls entered by the last named group that fowls of the same blood line may be encountered in later contests. The indications are that a variety of strains and methods of breeding entered into the production of the sample of fowls used in this study.

Of the 790 fowls submitted, the first year laying records of 655 are available for study. The records of 135 birds were omitted for various reasons. The chief causes of omission were death which prevented the completion of the full year's record and disqualification for disease or anatomical defect which interfered with egg production. In the early contests several pens of two year old hens were allowed to compete. The records of these have been omitted from this study which deals only with pullet or first year egg production.

VARIATION IN ANNUAL EGG PRODUCTION.

The annual egg records of all Barred Rock pullets included in this study are given in Appendix Table I. The vari

(1) A pen in the first (1911) and second (1912) contests consisted of five pullets; and of ten pullets in all later contests.

ation in annual egg production was very great, as it was found to be in the other breeds studied. The extremes of variation are represented by one individual which laid only one egg during the full year, and by two birds which laid 282 eggs each in the same period. Variation between these extremes was almost continuous, although as might be expected, the distribution is scattered and irregular as each of the extremes is approached. The records as given in this table have formed the basis for the analysis and discussion of variation in annual egg production which follow.

TABLE 1A

FREQUENCY DISTRIBUTION OF ALL BARRED ROCKS ON BASIS OF ANNUAL EGG PRODUCTION.

'20 Totals

2274

16

10

19

37

65

78

13 80

16 76

76

25

13

4

54 15 35 571 93 82 100 120 99 655

In Table 1a, the data of Appendix Table I have been grouped into classes of fifteen eggs each and separated by years to facilitate statistical treatment. The annual means and variation constants have been calculated from the data in this table. In Table 1b, the annual distributions of Table la

OF THE DOMESTIC FOWL

are stated in percentages so that each year may be compared directly with every other one. The frequency curve showing variation in annual egg production for all nine years taken together is shown in Fig. 1, which is a graphic representation of the data in Table 1b.

TABLE 1B

PERCENTAGE FREQUENCY DISTRIBUTION OF ALL BARRED ROCK PULLETS ON BASIS OF ANNUAL EGG PRODUCTION.

Totals

100.2 100.2 100.1|100.3 100.1| 99.9 100.0 100.0 99.8 99.8

In examining these tables it must be noted that the numbers of records included in the separate years are not equal and that some totals are very small. Thus in 1912, only fifteen records are available for study, while in 1918, the total number is 120. Bearing this fact in mind it is evident that the distribution of egg production in the separate years is in general similar. The great bulk of the birds in each year laid between 100 and 200 eggs. The range of egg production while it is very large in all of the years appears to be somewhat less