774 REPRODUCTION AND MIGRATION IN BIRDS 



hr day laid many of their eggs in the dark, usually within the two 

 hours before onset of light. Such ovipositions were regularly fol- 

 lowed by ovulation. Apparently the timing of oviposition bore the 

 same relation to onset of darkness whether the dark period was 12 

 or 10 hr. 



{b) Continuous uniform lighting. Under continuous and uniform 

 illumination (daylight excluded), Warren and Scott (1936) found 

 that hens laid at any hour of the twenty-four. Records of individual 

 hens indicated that the usual intervals between successive eggs were 

 somewhat greater than for the same hens under normal photoperiods. 

 Intervals of greater length, presumably corresponding to the interval 

 between sequences under natural photoperiods, occurred with some 

 regularity, but with lesser frequency than under usual lighting con- 

 ditions. According to Warren and Scott, neither exercise nor restricted 

 feeding (6:00 a.m. to 6:00 p.m.) prevented lay of eggs over the 

 24-hr period. 



McNally (1946) confirmed the findings of Warren and Scott 

 (1936) in battery-caged hens when feed was available at all times. 

 When feed was available for only 12 hr of the twenty-four, however, 

 the continuously lighted hens observed by McNally laid a considerably 

 larger proportion of their eggs during the 12 hr of feeding with light 

 than during the equal period of light without available feed. 



Fraps et al. (1947) subjected battery-caged hens previously main- 

 tained for several months under a 14-hr photoperiod (daylight ex- 

 cluded) to continuous illumination, with water and ample feed always 

 available. Over a period of 4 weeks, the hens continued to lay out 

 their sequences almost exactly as they had under the 14-hr photo- 

 period. When the continuously lighted hens were allowed feed only 

 from 8:00 a.m. through 4:00 p.m., practically all eggs came to be 

 laid between 6:00 a.m. and 6:00 p.m. When allowed feed between 

 8:00 P.M. and 4:00 a.m. the periodicity of lay was reversed. 



Wilson and Abplanalp ( 1956) reported that hens under continuous 

 illumination (daylight excluded) laid a larger proportion of eggs dur- 

 ing afternoon and evening hours; however, a good number of eggs 

 were laid during every hour of the twenty-four. The pattern of lay was 

 attributed to feeding and management practices. 



(c) Continuous nonuniform lighting. Warren and Scott (1936) 



