762 



REPRODUCTION AND MIGRATION IN BIRDS 



Table II. Summary of Experiments with Male Bobolinks Captured during North- 

 ward Migration in Early May, 1956 (35° 47' N. Lat.) and Exposed to 16-hr Photo- 

 periods until October 1 (Two males in each group) 



" Pigmentation experimentally produced through daily injections of 20 ng testosterone 

 propionate May 16 to 28 and May 30 to June 4; still quite black June 13, but returned to 

 neutral sometime before July 31. 



EXPERIMENTS AND RESULTS 



The experiments and results are summarized in Tables I and II. 

 All the bobolinks used were captured in fowling nets at the same 

 locality, near Raleigh, North CaroHna, during early May from north- 

 wardly migrating flocks. They were held through the summer on 16-hr 

 photoperiods. During August all the birds molted, more or less com- 

 pletely, developing essentially "henny" plumage, and the black pig- 

 ment disappeared from the beak. They then were exposed to various 

 photoperiods beginning September 15 (Table I) or October 1 (Table 

 II) in ventilated, light-tight compartments. In each compartment two 

 100-watt white fluorescent tubes delivered about 150 ft-c of light to 

 the floor of the cage. 



