? 
riid-ir Feb. late Feb. late fey raid -July early Oct. early Nov. mid-Nov, 
6 ( 10 <#) 
325 (47*) 
436 (63#) 
75 (0 #) 
9 ( 86 #) 
240 (56#) 
83 
26 (6 #) 
second the 
The first figure represents the estimated number^ of nests, the 
,ewVo.c^«g 
of nests found containing eggs. 
The first eggs are laid in January or February as indicated by the two 
February counts given above but the peak of laying is probably from March 
through June. In November of 19 63 and 1964 there were still a number of 
large young present which must have hatched from eggs laid about 75 days 
before, perhaps in early August. 
The annual cycle in this species is apparently less variable than in 
most other species breeding in the central 
There also seems to 
be a more gradual increase and decrease in nesting activity than in most other 
nesting species. However, the laying peak in 1964 must have occurred some¬ 
what later than in 1963 since a significantly larger( p "> .99/^proportion 
of the nests contained eggs in July, 1964. 
Reproduction 
; The tropicbirds nest in a variety of habitats on Enderbuiy and are 
concentrated in areas favorable for nest sites* 
They nest under slabs of coral along the west side 
of the island and to a lesser extent on the south and east sides* The k8xx±sss.t largest 
concentration of nests in sucjr sites is several 
hundred yards north of the lighthouse* In this area tropicbirds also nest around the 
remains of the colonial installations under old drums and other debria. f 
In the interior of the island alternating layers of hard and soft guano 
rock have been exposed at the edges of the old guano diggings. Weathering 
has produced uneven wear on the different layers and an overhanging ledge 
has been formed around the edge of the excavated area. Approximately 150 
pairs of tropicbirds nest under these ledges and in some places several 
nests are situated within a few feet of one another. 
A third nesting area is found in the Cordia groves at the south end 
of the island. Here the birds nest under the fallen tree trunks and in 
the heavy undergrowth along the periphery of the gloves. Tn the same area 
they also nest in "houses” built 
