Blue-faced Booby Estimated population* —-: 2000 + 15% 
(Sula dactylatra) Estimated breeding population ——: S00 +_ 10% 
Estimated non-breeding population: 1200 jh 15% 
Nest count: -total nests counted : 206 
Nests/ one egg 13 
Nests/ two eggs 10 
Nests/ egg 8c naked chick 0 
Nests/ small downy young 37 
Nests/ large downy young 62 
Nests/ immature ?8 
Estimated % nest count complete—: 60% 
Berlese samples taken-*-: 2 
Sera samples collected-125 
Number of returns-—: 143 
Number banded---: 38 
Even with due allowance for disparate count techniques and other 
possible sources of bias,the number of nesting Blue-faced Boobies can 
be said to definitely have decreased from the previous month. In the 
table below is given the percent of nests in different stages of nest 
ing from July to August, 1966 
Comparison of Nesting Stages of Blue-faced Boobies on Howland Island 
__ in the Months of July and August, 1966 
Contents of nest % of nests in each % of nests in each % of nest in each 
nest stage in July, nest stage for July nest stage in 
1966 nesting population August,1966 
in August ,1966 
One egg 
10 % 
4 % 
6 
% 
Two eggs 
20 % 
5 
% 
Egg 8c Naked 
young 
0 % 
0 
cf 
70 
Nalied young 
12 % 
23 % 
3 
0 / 
' 21 % 
Small downy 
young 
18 
% 
Large downy 
young 
ca. 47 % ' 
33 % 
30 
C / 
/O 
Immatures 
ca* 11 % 
41 % 
38 
0 ' 
/O 
Although not readily apparent from the table the nesting stage at 
which most of the decrease occurred was apparently the egg stage or shortly 
thereafter# Other observations made during the August visit suggest that 
about 70% of the nests with eggs present in August contained fresh eggs# 
If the percent of nests present in August is adjusted for those nests 
