SOOTY TERN (Sterna fuscata): At-Sea Distribution and Abundance 
The following maps represent all At-Sea observations made by 
personnel of the Pacific Ocean Biological Survey Program from February, 
1963, through August, 1965* 
Each square represents one days observation from the first through 
the fifteenth of the month, while each circle represents one days 
observation from the sixteenth through the thirty-first of each month. 
Numbers refer to number of birds per observation hour ( * = less 
than 0.5 birds per hour). On the average each hours observation represents 
ten linear ship miles of observation. 
Colors represent a subjective evaluation of distribution in terms 
of abundance. 
Color code: 
= () birds per 
— *_X0 ** ** 
= 11-50 
— ■•= 51-100 
mm = 100 + " 
