
PART II. SOOTY TERN STUDIES 
Populations 
During the first week of March a few sooty terns began to 
circle in the evenings over the southeastern portion of Sand Island 
and over Runway 6-24, By March 15, the flock had increased to several 
thousand birds, and they began to rest on the ground during the night. 
After that there was a gradual increase in numbers, and they soon began 
to settle on the ground during the daytime. 
The first egg was laid on May 11. Following that, laying 
progressed rapidly. On May 30, we conducted a census of the sooty tern 
population on Sand Island. There were three distinct colonies occupy- 
ing a total area of 420,000 square feet. Counts on ten randomly 
selected sample plots, each 10x10 feet, indicated an average of 11.6 
eggs per plot. From this a total of 48,720 eggs was calculated. The 
nesting population, allowing two adults for each egg, was therefore 
97,440. Adding an estimated 50 percent for birds in the air which had 
not yet established nests, a calculated total of approximately 150,000 
sooty terns was present on the island at that date. After that an 
undetermined number of additional birds arrived at the island. 
Control Exmeriments 
Since the sooty terns are expected to be a problem in the 
event that jet aircraft use Midway, control experiments were conducted. 
. 
Harassment Progr 
As a result of discussions with Dr. Martin Moynihan of Harvard 
University, who has made intensive studies of the behavior of gulls and 
terns and who was visiting Midway at the time, it was decided to in- 
stigate a harassment program directed toward driving the sooty terns 
away from their nesting grounds. This program was begun with the co- 
operation of the Navy on March 19. Considerable material and manpower 
were invested by the Navy in this experiment which was terminated on 
May 11. A total of 65 man-days (exclusive of time put in by the Marine 
Guard, the biologists, and Lt. Picht) were used on this project. A 
total of 2238 gallons of diesel oil was burned, and 890 aircraft 
distress signals, 107 aircraft float lights, 750 l2-gauge shotgun 
tracer sheels, and 2025 12.~gauge shotgun 00 buckshot were used. 
Procedure was as follows: 
March 19 to April 12. Once during each patrol, at approxi- 
mately hourly intervals, the Marine guards stopped at the area where 
the sooty terns were settling on the ground and fired red and green 
flares into the flocks. After about two weeks the flare supply was 
depleted and smoke flarelights were burned on the ground. The terns 
were not kept off the ground entirely during this period, but they 
were considerably upset. 
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