Crossin's nest count suggests that at least two laying peaks occurred 
in this colony, a distinctly unusual phenomenon, since these birds usually 
have a single pronounced annual peak in the nesting cycle. Since most of 
the eggs were rather well incubated, one laying peak probably occurred 
about two months earlier, or in mid-May* The large numbers of medium-si zed 
young suggest that another laying peak occurred about four to six weeks 
earlier, or from late March through mid-April. 
Table 6 below compares population data for the four POBSP July surveys 
of Howland Island. 
Table o. Comparisons of July populations of Lesser Frigatebirds on Howland 
Island in 1963, 1964-, 1966, and 1968. 
Estimated population 
°Io of nests/eggs 
°jo of nests/young 
Probable egg peak 
1963 
July 6-H 
10,000 
10 0 # 
1964- 
1966 
10,000 
c. yQ°jo eggs 
or small yg. 
10,000 
c *60^ 
c .4-0 °jo 
968 
July 22-25 July 12-22 July 16-18 
35,000 
4 - 8 ^ 
5*7° 
mid-late June mid-late May late May late Mar-mid Apri 
mid-May 
The data presented above suggest a much larger proportion of the popu¬ 
lation nesting earlier than usual (as was apparently true for the Great 
Frigatebirds); it may also indicate a substantial increase in the size of 
the nesting population. The estimates for the earlier visits were more 
often "visual estimates" and, as such, may have been substantially less 
accurate than the July 1968 estimate. Ho previous estimate was higher 
than 10,000 birds; I think it likely that the 1968 population figure 
properly Indicates larger population, particularly since both Crossin and 
I were present in July 1966, as well as In 1968, and both of us believe 
that the number of these frigatebirds present was decidedly greater this 
July. In addition it may be noted that a very careful estimate made on 
McKean also resulted in a population figure for this year that was about 
twice the highest previous figure. 
as a 
The single return, a white-headed subadult, 74-7-64-398 had been banded 
nestling on Phoenix Island In Hovember 1964-. 
Sooty Tern Estimated population --—-— 375,000 * 
Estimated breeding population---- 306,000 
Est. c p of breeders/nests/eggs-- 70 
Est. c jo of breeders/recently hatched young -- 25 
Est* °jo of breeders/somewhat larger .young --- 5 
Ho. of returns ~~ 14-1 (A-U - all breeding birds) 
« 
Sooty Terns nested mostly in two large colonies at the south end of 
the island. The southernmost colony, about 1500 feet long by 60 feet 
wide, was estimated to occupy about 225,000 square feet and to contain 
* Almost all data on this species were taken by Crossin. 
