3 
Several stages were noted in the nesting colony; (l) Adult birds 
sitting on eggs, (2) Adult birds sitting on new nests without eggs, (3) 
Adult males sitting on nests being constructed, some with inflated gular 
pouches, and (4) adult males sitting in the colony with inflated gular 
pouches and no nesting material present. 
On 18 April 8? eggs were counted; 24 hours later 119 eggs were counted. 
Two nesting areas counted had 20 eggs and 83 new nests without eggs. An 
egg flotation test was run on 40 eggs; 39 were lightly incubated and one 
was medium incubated. Of these 40 eggs, 20 eggs checked lay flat on the 
can bottom, while in another nesting area one egg checked showed medium 
incubation and 19 were lightly incubated (with one end of the egg pointed 
toward the top, indicating 5 + days’ incubation). 
I counted birds from the Lighthouse on the l8th and 19th. Three 
thousand birds were counted on both occasions: 1500 flying immatures still q 
roosting on the nesting sites where they were raised, and 1500 adults in 
the new nesting colony. 
Gray-backed Tern 
Several were heard calling over the island on 19 April. 
Sooty Tern 
■ . *• 
A Sooty Tern breeding cycle is almost finished on Howland. Seventy- 
five percent of the immature birds were capable of sustained flight al¬ 
though less than 50 percent are actually leaving the island to feed. 
Young birds can be seen all over the island and along the reef. Probably 
less than 25 percent are capable of feeding themselves without parental 
help. Flocks found feeding near Howland were composed of approximately 
25 to 50 percent immature birds. These immature birds would follow Wedge¬ 
tailed Shearwaters around close to the water, instead of flying 25 to 50 
feet above the water and diving to the surface like adult Sooty Terns. 
Apparently watching adults feed as well as trial and error is part of the 
process of learning to feed. 
The nesting colony was stepped off and diagrammed for comparison with 
January dimensions obtained by Ken Balcomb. The numbers each of us ob¬ 
tained are relatively close. Balcomb recorded 391*500 square feet and for 
that same portion of the nesting colony I recorded 362,700 square feet. 
These differences, using Balcomb*s nest density figures,' amount to a dif¬ 
ference in calculated population of only 7 5 200 nests. A diagram of the 
nesting colony is included in this report. 
There are two more subpopulations nesting which were not present dur¬ 
ing the January visit. In both of these subpopulations less than 50 per¬ 
cent of the immature birds were flying, indicating a later nesting group 
of birds. Balcomb in his January report stated there were birds sitting 
down in these areas, but not nesting. These two subpopulations account 
for 8l,225 square feet of nesting area. At present approximately 443,9^5 
square feet are occupied by nesting Sooty Terns. 
