BULWER'S PETREL (Bulweria bulwerii): 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 the actual number of birds observed during the day. Color code: yellow = 0 birds green = 1-10 birds blue = 11-50 birds red = 51-100 birds brown = 100+ birds