5 
THE BROWN BOOBY 
[The adult Brown Booby is about 
thirty inches long, with dark brown 
upperparts and a white belly which 
is in sharp contrast to a brown 
breast. In the Central Pacific, 
Brown Boobies of both sexes have 
completely brown heads, while in 
the Eastern Pacific males have 
either white or gray heads. The 
plumage of the young birds is 
brown, but the belly is slightly 
lighter than the upperparts . With- 
in two years these young birds will 
attain the brown and white adult 
pattern. 
Male adult Brown Boobies can 
be distinguished from females by 
their calls and bill coloration. 
The male’s call is a high-pitched 
whistle, while the female’s call is 
a loud honk. Males have a dark 
area around the base of the bill 
which turns blue during the nest- 
ing season; the female’s bill is 
bright yellow at the base with a 
dark spot in front of the eye. 
Brown Boobies are found on 
many uninhabited Islands across the 
entire Pacific. Although this 
species numbers in the thousands, 
only a few islands support popula- 
tions greater than a hundred birds . 
The reasons for their rela- 
tively small numbers, compared with 
the closely related Red-footed and 
Blue- faced Boobies, are unknown. 
One difference between Brown Booties 
and the other two species that 
could relate to this problem is the 
wary nature of the Brown Boobies. 
While Red- foots and Blue- faces 
allow people to approach their 
nests before they take flight, 
Brown Boobies generally fly off 
long before observers reach the 
nest. It is interesting to note, 
however, that when birds of this 
species have continuous contact with 
man, they become quite fearless. 
In fact, on several occasions POBSP 
field personnel have been attacked 
by adult Brown Boobies when they 
wandered too close to nests. 
Like many Central Pacific sea- 
birds, the bulk of the Brown 
Booby’s diet is flying fish. It 
also eats squid and various reef 
fish, such as blennies . 
To catch their food Brown 
Boobies dive into the water, some- 
times from heights of fifty feet or 
more. Occasionally they catch fly- 
ing fish from behind in mid-air. 
The presence of reef fish in 
the diet of this species suggests 
Adult male Brown Booby with chick. 
Photo by Philip C. Shelton 
