Annual Variation in Numbers of Brown Boobies Breeding on Howland Island. 
FIGURE 
70 
4o 
30 
20 
10 
0 
J 
.I „ „, t 
_ 
——-—— 
-- 
n \ \ 
T 
\ 
1 / 
1 
j 
i 
. 
, 
i 
£ f 
N 
-3—- 
• 
... 
_ 
: 
: 
. i 
.. ■ 
A 
P 
r 
J 
u 
1 
0 
c 
t 
J 
a 
n 
A 
P 
r_ 
J 
u 
1 
0 
c 
t 
J 
a 
n 
A 
P 
r 
J 
u 
1 
0 
c 
t 
J 
a 
n 
A 
o 
•r 
^° r 
i <A1*- «. 
J 0 
tl c 
1 t 
-rr~v ■ - -- -JT/yv ' 
1963 
1964 
1965 
1966 
: Actual breeding population counted by the POBSP 
\u? "y 6l vvVC^ 
q : Estimated breeding populations. These points represent the very probably minimum number praesnt. 
They are derived from extrapolation from known counts making the assumption that the incubation 
period is about 1 l/2 months and the fledging period about k months. 
