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NORTHERN GRID SURVEY NO. 31 
PRELIMINARY REPORT-NORTHERN GRID, SEPTEMBER 1966 
By Paul W. Woodward 
From the night of 10 September 1966 until the morning of the 12th, the 
U.S.N.S. SHEARWATER passed through the Northern Grid on the way to the Howland- 
Baker area. During this time continuous bird observations were made by the 
Smithsonian Party consisting of Paul Woodward (Biologist-in-Charge), Walter Bulmer, 
Richard Chandler, John Fitch, Richard Heiden, Dave Hoff, Larry Huber, Frank Smith, 
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Chris Thompson, and Robert Tuxson. The course followed (see map) was designed to 
cover as many of the different areas of the grid as time would allow. 
Diurnal observations (sunrise to sunset) covered 147 miles in 966 minutes 
while nocturnal observations were made for 2l4 miles and 1310 minutes. A total of 
722 birds of 15 species was seen during the day and 78 birds of four species were 
recorded during the night. Weather conditions were favorable during the trip. 
Sooty Terns and Wedge-tailed Shearwaters were the dominant species in the area, 
accounting for about 8 l # of the birds seen. Pterodroma externa was the next most 
common form. All other groups were seen in low numbers. No boobies were seen 
during the day. Only one abundance center was found in the grid in the southwest 
corner where in one hour and fifteen minutes 467 birds were seen in four flocks. 
The last complete survey of the Northern Grid in September occurred in 19°4. 
During this timae large numbers of migrant Sooty or Slender-billed Shearwaters were 
moving through the area. Only three of these birds were seen during the present 
cruise. Density of birds was much greater this year than two years ago-3.4-l.53• 
However, this may be due to a sampling error, i.e., we happened to hit the area 
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where the birds were concentrated in a short period of time, but if we had traveled 
more in the grid we would not have seen an equivalent number of birds. There are 
indications that some birds were more abundant this year regardless of the area we 
traversed. For example, 206 Wedge-tailed Shearwaters were seen in 1964 and 339 
