8 
numbered more than 30,000 and the 
entire population was more than 
95,000. 
On March 27, 1967 , when Pal- 
myra was visited again, over 95,000 
eggs were observed in the airstrip 
colony. Some of the nests contained 
two eggs, which is not the normal 
clutch-size of the Sooty Tern. 
About 5 percent of the eggs had 
hatched. The oldest chicks were 
about 4 days old. 
The importance in the role of 
the parent birds in the survival of 
the egg or chick was demonstrated 
during this visit. The parent birds 
shaded the egg or chick from the 
midday sun by standing over them 
until an approaching intruder ac- 
tually threatened them. Once the 
chicks were able to move about on 
their own other adults would chase 
them away from their nests as they 
did other intruders. I did not de- 
termine whether or not the parent 
birds recognized their own young. 
Two new nesting sites were 
found during the March visit. They 
were on an abandoned causeway and 
were small colonies of only about 
100 birds each. There was no major 
change in the population of the 
terns occupying the runway, even 
though it was frequently used by 
aircraft . 
I believe that the breeding 
population of Sooty Terns on Pal- 
myra has increased due to the con- 
struction and subsequent abandon- 
ment of the airbase. Construction 
of the airstrip cleared away heavy 
vegetation and the occasional reno- 
vation of the strip has maintained 
the clearing for the terns. 
Naturally clear areas on Pal- 
myra include only a few small coral 
islets and Barren Island. These 
areas are subject to frequent flood- 
ing and probably could not support 
the present breeding population of 
Sooty Terns. This new man-improved 
Sooty Tern Breeding ground will be 
utilized as long as the airstrip is 
occasionally renovated. Should the 
airstrip become heavily overgrown, 
this Equatorial Pacific breeding 
ground probably would be lost . 
The # Sooty Terns on Palmyra 
demonstrate one of the ways wild- 
life can adapt to man’s activities. 
Contributed by 
Christopher C. Mathewson 
Lieutenant Junior Grade 
-wi.. . ^ ■ 
Sooty Tern Nests 
Notice the one with two eggs. 
Photo by C. C. Mathewson 
The Pacific Bird Observer is a< 
newsletter distributed to col- 
laborators of the Pacific Ocean] 
g Biological Survey Program of] 
rg the Smithsonian Institution in; 
S order to promote a better; 
§ understanding of birds and' 
2 their relation to man in the] 
Pacific . 
