4 
1963 
1964 
1965 
The Blue-faced Booby population on Enderbury is composed of a number 
^ 0 °^ X 
of s ubunits , Th^-pispuftaf divided^into^-^ub^populationsadult 
birds which are nesting, have nested in the past or are about to nest; 
subadult and non-breeding birds; and adult birds which breed on other islands. 
The subadult and non-breeding component of the population roost in one or 
more large clubs while tfeeident birds roost, for the most part, singly or 
in pairs, usually near their nest sites. 
The location of the clubs is fairly constant although all club sites 
may not be utilized each night and individual birds may roost in different 
clubs on different nights. c& e - WoV< 
The clubs- are primarily cor^o'sed of young birds from Enderbury or other 
islands «andlc^ily about 25 percent of the birds are breeding adults. The 
size of the clubs varies from month to month and only a fraction of the birds 
found in clubs are on the island any given night. We estimate that about 
2000 to 2,500 birds roost in the clubs in a period of a year. 
Annual Cycle ; The infrequent t'fips to the island and the long period between 
trips make it impossible to define the annual cycle accurately. In most 
years there is probably some egg laying throughout the year. In February 
V 
1964 there j>f €re no nests or young present. 
iU. e,<oX\ 
Table _presents the Blue-faced Booby nest counts for ali secern 
POBSP visits. Large numbers of eggs are first laid in late March wft t r egg 
laying reaches its peak in June. Smaller numbers of eggs are still being 
laid in October but there ms relatively little breeding in mid-Winter. 
Table , Nests Counts of Blue-faced Booby on Enderbury Island 
mid-Feb. late Feb. late May mid-July early Oct. early Nov. mid-Nov. 
0 (0056) 
396 ( 69 $) 
424 ( 52 $) 
/ 
101 ( 29 $) 
tsast t.at» r«Ti fee-* 
311 ( 20 $) 
18 ( 33 $) 
74 ( 66 $) 
28 ( 36 $) 
The first figure is the rumber of nests and the second the percentage containing 
Reproduction : Blue-faced Boobies nest on all parts of the island but the 
heaviest concentration of nests is on the west side from the "guano hill" 
to the south end of the island. In July 1964 the area from the lighthouse 
