. The primary concentrations of nesting birds were in much the same 
areas this July as they were in July 1966 . Perhaps the densest nesting area 
was along the southwest corner of the island, from the tower on the west 
side to the point where the island curves sharply to the east. This area, 
which comprises less than an eighth of the island surface, contained about 
21 percent of the nests. Birds were also numerous on the north and west 
perimeters of the island but were decidedly less numerous along the east 
perimeter and were least abundant along and across the south end of the 
island. 
If these figures are then applied to the nest count we can arrive at 
an estimate of the proportion of the breeding population that had eggs in 
various stages of incubation. The results of my calculations thus indi¬ 
cate that 18.9 percent of the population was on fresh eggs, 18.6 percent 
was on very .slightly incubated eggs, 10.4- percent was on slightly incu- 
Dated eggs, 11.9 percent was on moderately incubated eggs, and 2.6 percent 
was on heavily incubated eggs. If the categories of young are assigned 
ages based on the subdivisions of the nest count, then naked young would 
have been from 1-2 weeks old, small downy young would have been 3 - 4 - weeks 
old, large downy young would have been 5-7 weeks old, large feathered young 
would have been 8-10 weeks old, near immatures would have been about 11-17 
weeks old, and dependent immatures would have been about 18-19 weeks old 
(aging vide R. Schreiber); we can hereby derive an estimate of what pro¬ 
portion of the population laid in the preceding half-month periods. My 
calculations along these lines would indicate that: from 19 to 28 percent 
of the birds presently nesting had laid during the first half of July, 19 
to 29 percent had laid during the latter half of June, 15 percent had laid 
during the first part of June, about 4- percent had laid during the latter 
half of May, about 6 percent had laid during the first part of May, about 
9 percent had laid during the latter half of April, about 8 percent had 
laid during the first half of April, about 6 percent had laid during the 
latter half of March, and about 3 percent had laid during the first half 
of March. The remaining 4- percent had probably laid before this period, 
as early as December or January. 
If these figures are at all appropriate estimates of what occurred 
on the island prior to our visit they seem to indicate a higher mortality, 
or lower nesting rate during the month of May than would be expected during 
a normal laying season. It seems likely that' such a bad period may have 
occurred in view of the bi-modal peak in laying in the Lesser Frigatebirds 
which suggests the possibility of subnormally little laying in early May, 
and in view of the high incidence of rotten eggs among nesting Brown Boobies. 
Three clubs were seen on 17 July. One near the southeast corner of 
the island, contained 55 birds at 1230 , most of them subadults but in¬ 
cluding two immatures. About an hour later, another club was seen on the 
east beach crest about due west from the lighthouse". This club contained 
about 95 birds, many of them were in apparently full adult-plumage-, but 
many were subadults (perhaps 50 percent); a few immatures were present. 
Hackman noted a third club, consisting of 23 birds, 10 subadults and two 
immatures, north of the lighthouse at 1715 * In view of past observations 
of clubs of this species it seems likely that the nocturnal club observa¬ 
tion must have been at least twice as large (about 350 birds). The east 
