LIMITED TRAPNESTING 9 



LIMITED TRAPNESTING FOR ESTIMATING 

 HATCHING-SEASON EGG WEIGHT 



In this locality the normal hatching season includes March and April. During 

 this period pullets should be producing hatching eggs of maximum size for the 

 first laying year. In this study the mean weight of eggs laid in March is con- 

 sidered to be the hatching-season egg weight. Since it is desirable to use hatch- 

 ing eggs from pullets, only if these eggs are to average about 25 ounces to the 

 dozen, considerable care is necessary in selecting for egg size. Several short- 

 time measures of egg weight may be applied in estimating hatching-season egg 

 weight. 



Table 5 gives the correlation coefficients, the calculated and actual hatching- 

 season egg weights, and the percentage accuracy of the short-time measures used. 

 The hatching-season egg weights as calculated by the straight line regression 

 equations are compared with the actual weights in Table 6, although none of the 

 regressions was strictly linear. 



A satisfactory estimate of hatching-season egg weight may be obtained from 

 limited records, except in the case of birds which lay very small eggs up to Jan- 

 uary 1, and these would probably never be used for breeding. Three short-time 

 records seem to be satisfactory. Continuous weighing up to January 1 has some 

 advantages. Weighing all eggs laid during the first week of October, November, 

 and December is very satisfactory; and weighing on the first two days of these 

 three months gave very good results. Weights taken for the month of Ocober 

 were not a safe criterion of hatching-season egg weight. 



Table 5.— The Value of Limited Trapnesting for Estimating Probable 

 Hatching-Season Egg Weight. 



Kinds of Number Correlation Hatching-Season Accuracy 



Limited Trapnesting of Coefficient Egg Weight — March Per- 



Birds Grams cent 



Estimated Actual 



A. First 2 days of Oct., Nov., Dec. 695 .6939 +.0133 56.8 60.5 94 



B. First week of Oct., Nov., Dec. 705 .7196 ±.0122 59.8 60.4 99 



C. Daily, October only 639 .6795 +.0144 57.7 60.6 95 

 E. Daily from first egg to Jan. 1 539 .7427 +.0130 58.9 60.6 97 



