778 REPRODUCTION AND MIGRATION IN BIRDS 



Bastian and Zarrow (1952) is "asynchronous" from day to day by 

 the extent of lag. 



Times of successive ovulations in the sequence may be estimated 

 from times of oviposition (Rothchild and Fraps, 1949), or lag values 

 in the ovulation sequence may be estimated directly from lag values 

 in the oviposition sequence (Fraps, 1955b). Lag of the second ovula- 

 tion of the sequence shown in Fig. 1 is indicated by /7O2, lag of the 

 third ovulation by /7O3. Lag values for ovulation sequences, calculated 

 from the extensive data of Heywang (1938) on length of interval be- 

 tween successive eggs, are shown in Fig. 2 for sequences of 2 to 13 

 ovulations. The solid part of each column in each histogram repre- 

 sents lag with respect to the preceding ovulation (daily lag). The 

 height of solid plus lined columns represents cumulative lag at suc- 

 cessive places beyond the second of each sequence, total lag in each 

 sequence being so measured at the last position. 



There are obviously some well-defined regularities in the lag pat- 

 terns of Fig. 2. Lag in the first place (there is only one place where n 



o 



i 



■ 



8 



,1 



< 



SEQUENCE LENGTH 



Fig. 2. Lag in ovulation sequences numbering 2 to 13 members. 



