Comparisons of this July population with those observed in previous 
years indicate that the population is at about its optimum level (see Table 
k below). The breakdown of the nest counts indicate that the population 
continues to have a rather diffuse nesting cycle with almost all stages of 
nesting usually being present during July 0 
Table k. Comparisons of July nest counts of Red-footed Boobies on Howland 
Island in 1963 ? 196^ 1966 , and 1968 . 
1963 
1964 
1966 
1968 
Dates of visit 
July 6-8 
July 22-25 
July 12-22 
July l 6 -l 8 
Estimated population 
Breeding population 
50 
150 
270 
# of nests counted 
11 
40 
27 
40 
$ of nests/eggs. 
64$ 
28 $ 
30 $ 
39$ 
$ of nests/naked or small 
yg• 36 $ 
20 $. 
33 $ 
22$ 
$ of nests/large young 
— — 
53$ 
37 $ 
39$ 
• 
The only subadult returned was 
a bird that had 
been banded on 
Enderbury 
in January 1967- All other returns were of birds that had been banded in 
Howland. 
If only complete clutches (those testing slightly to fully incubated, 
excluding clutches known to contain rotten eggs) are tabulated, the mean 
clutch size of 10 clutches is 2.0. 
Detailed nesting data were taken with the k5 returns obtained and are 
presented in Appendix 3 * Forty-two of the k5 returns had been banded on 
Howland; the other three, two birds roosting and one breeding bird with 
two eggs, had been banded on Enderbury. 
Great Frigatebird Estimated population-k8C 
Estimated- Ho. of nonbreeders present- 50 
Estimated breeding population - V 30 
Results of sample nest count (Believed 
to be more than 95 percent complete) - n 21k 
Hests/eggs---*- 2o (12.1$) 
Nests/naked young- 9 (k.2$) 
He sts/small downy young--- 17 (7•9%) 
Hests/medium downy young--- 27 (12.6$) 
Hests/large downy young —--- 8k (39*3$) 
Hests/large, nearly fully feathered yg 51 (23*8$) 
Ho. returned — 3 (2 A-M, 1 A-F) - 3 
breeding birds) 
Great Frigatebirds nested in and around the dead Cordia grove in the 
center of the island where they have nested in the past. They appeared to 
be somewhat more numerous towards the south’ end of the area and the Red¬ 
footed Boobies were more abundant in the taller trees to the north but the 
