Brown Booby ( Sula leucogaster ) 
Current Status : Common resident, nesting in small numbers. Maximum POBSP 
population estimate; 3000 in November 1963- Minimum POBSP population esti¬ 
mate; 100 in July and November, 1964. 
Prior Records : Cassin ( 1858 ) reported that the species wax present on 
Enderbury in 1840 or l84l. James E. A. Kinney banded 50 adults on May 3? 
1939. 
Population ; Over 150 adults have been banded and in February ,^ 1965 ,approx¬ 
imately 50 percent of the 60 birds observed were banded. This would indi¬ 
cate that the population is only slightly larger than the 300 estimated in 
November, 1963 ^and that only about 50 percent of the population is present 
on any one day. 
Annual Cycle : We have not been able to determine whether or not Enderbury 
Brown Boobies have an annual cycle. IVeve Vs'oe 
Reproduction ; In July 1964 about half of the Brown Booby nests were con¬ 
centrated in a fairly limited area along the west side of the island either 
near the colonists 1 house or at the south end of the island, and another 
small concentration, composing about 1/5 of the nests, was located on the 
southeast corner of the island. The rest of the nest sites were scattered 
over the island but individual nest sites were usually located in the same 
area on subsequent tfips. The nexts on the east side of the island were 
behind the beach slope in small depressions, sheltered in some way from the 
prevailing winds. Those on the west side were usually on slightly elevated 
ridges or in large open areas. 
Table 
1963 
1964 
Number of Brown Booby nests on Enderbury Island 
mid-Feb. late Feb. late May mid-July 
“—"T* —— 30 (33%) 
early Oct. early Nov. mid-Nov. 
43 (7950 
9&MMOS 
1965 
13(31$) 
37 (3050 
25(4450 
41 ( 80 *) 
39 (2150 
6 ( 8350 
A xir*.--’ u is uhe nmn.be c ox nesis } th@ second is the percenta.s?e 
of nests containing eggs. ____ 
