FERTILITY IN RHODE ISLAND REDS 3 



The collection of hatching eggs for these weekly hatches covered about 52 

 days. During this period there was the normal increase in length of day, with 

 something of an increase in the amount of sunlight. Since the birds were confined 

 in the house, they had practically no direct sunlight; but they did have a some- 

 what longer feeding day as the season advanced, since no artificial lights were 

 used. It is believed, however, that wide fluctuations in temperature during the 

 period and the prevailing low temperatures might have been the most important 

 external factors affecting fertility. 



Temperature is known to affect the activity of birds. Exposure to low tempera- 

 tures in breeding pens that are poorly insulated is believed to reduce the activity 

 and normal physiological functions of birds. Frostbitten combs and wattles 

 make males so uncomfortable that they mate infrequently. Females, too, are 

 likely to spend more time on the roosts. The data bearing on temperature and 

 fertility are summarized in Table 1 and illustrated graphically in Chart 1 by com- 

 bining the late- and early-hatched groups. 



100 



100 



2 3 4 5 6 7 



HATCHES 



Chart ]. Relation Between Temperature and Fertility. 



Table 1 shows the number of females bred from, the number of eggs, the mean 

 outside temperature during the time the eggs were laid, and the mean fertility 

 as calculated by averaging the fertility records of the individual females for each 

 of the eight hatches. 



For the ten-year period from 1922 to 1932 the average temperature increased 

 about 17 degrees from February 22 to March 5. The average outside temperature 

 during the time the first two settings of eggs were laid was below freezing. Fol- 

 lowing this period the temperature rose rather consistently to an average of 45.75° 

 at the time the eggs for the last two settings were laid. It seems probable that 

 these records over a ten-year period are fairly representative of what may be 

 expected in this locality. 



