SPECIES ACCOUNT 
Wedge-tailed Shearwater a = 1401 b = 152 c = 624 
Large numbers of light phase northern birds were encountered between Oahu 
and Johnston Atoll. Dark phase individuals, presumably southern hemisphere 
birds, amounted to only about 6 percent of the total in this area. South of 
Johnston Atoll the percentage of dark phase birds increased rapidly and 
remained close to 100 percent throughout the southern operations. Light phase 
birds were encountered again in numbers north of 5°N on the return trip. A 
total of six orange-streamered birds was recorded south of Johnston Island on 
10 September; of these, the last individual was seen during nocturnal observa¬ 
tions approximately 54 miles south of Johnston Island. 
Sooty/Slender-billed Shearwater a = l4,36l b = 900 c = 30 
The peak of the southward migration of these two species occurred during 
the period 12-21 September. Greatest numbers in the non-grid area were en¬ 
countered on 14 and 15 September north of Howland Island. Occasional high 
daily totals were recorded until 22 October, after which only a few stragglers 
were noted each day. It is difficult to differentiate between the two species 
by underwing linings when the birds are at a distance or when light conditions 
are changing. Flight patterns of the two species are similar and both forms 
appear to alter the pattern to meet sea and wind conditions, i.e., during 
periods of high wind and rough seas the birds usually fly in higher and more 
frequent arcs. Thus neither underwing color nor flight patterns could be used 
as positive criteria for separation of these species. 
A total of six specimens was collected. The first specimen, taken from the 
small skiff, is unquestionably a Sooty Shearwater. The other specimens, at 
least by measurements, all fall within the range of Slender-billed Shearwaters. 
These last five were collected from the SHEARWATER. All specimens had enlarged 
