14 



MASS. EXPERIMENT STATION BULLETIN 348 



LIMITED TRAPNESTING FOR ESTIMATING INTENSITY 

 Winter Clutch Size 



The relation of intensity to egg weight and egg production has been reported 

 by Hays (1944) and need not be reconsidered here. Suffice it to say that winter 

 clutch size is a very satisfactory measure of intensity and that intensity is one 

 of the most important inherited characters affecting egg production. In order 

 to breed successfully for increased egg production, it is necessary to select for 

 high intensity, and intensity can only be recorded by trapnesting. It therefore 

 becomes very important to learn what information on intensity may be secured 

 by limited trapnesting. 



The five short-time measures already used were studied to determine their 

 value for estimating winter clutch size, with results shown in Tables 10 and 11. 



Three methods of limited trapnesting were found to give a good estimate of 

 winter clutch size: trapnesting the first two days of each month from October 

 through February; trapnesting the first week of each month from October through 

 February; and trapnesting dail}' from first egg to January 1. Trapnest records 

 for October at the beginning of the year and for August at the end of the year did 

 not furnish dependable criteria of winter clutch size. 



Table 10. — The Value of Limited Trapnesting for Estimating Winter 



Clutch Size. 



* Regression was so definitely non-linear that figures calculated from a straight-line formual 

 were obviously inaccurate. 



Spring Clutch Size 



Large clutch size in March, April, and May is important in a laying flock. It 

 is desirable, therefore, to determine the usefulness of limited trapnest records for 

 estimating spring intensity. Results obtained by the five methods employed 

 are shown in Tables 12 and 13. 



In general, for estimating the probable spring clutch for the months of March, 

 April and May, the types of limited trapnesting may be rated as follows: A 

 trapnest record for the first week of each month is most accurate, followed closely 

 by trapnest records on the first two days of each month. The August trapnest 

 record at the close of the laying year also gives a good measure of previous spring 



