76 
T V" V 
Breeding birds are strongly land-dependent and a radially decreas- 
density pattern around the breeding island is typical, although in 
many cases the pattern of density is somewhat lop-sided due to local food 
concentrations. Nonbreeding birds are essentially completely land- 
independent and are supposedly distributed according to some set of 
oceanographic parameters. Two of these oceanographic features appear 
~o be the 5° N. and 12° N. areas discussed'previously. Birds in the 
5° N. belt around the surveyed longitude are probably the nonbreeding 
segments of the Howland, Phoenix group, Palmyra and Christmas Island pop¬ 
ulations . Christmas and Palmyra birds may in fact far outnumber the 
Howland-Phoenix birds, but this has not yet been demonstrated. I main- 
main, as mentioned^in previous species such as Phoenix Petrel, Wedge- 
nailed Shearwater, etc., that birds disperse after breeding, going east 
and west along the food-rich belt for long distances. 
The importance of the 5° N. zone on the biology of the southern 
island populations may be great. Preliminary investigation of 3T data 
indicates that the area may show significant cyclical annual change, and 
it may very conceivably be that the stimulus for initiation of breeding 
cycles comes from changes in this belt. This would help explain, for 
instance, the regularity of the Christmas Island cycles; in that the cur¬ 
rent changes which are regulated by temperate zone water masses may be 
the most pronounced and regular "clocks" in an otherwise uniform en- 
vironment. 
A Sooty Tern flock chased closely by a small vessel on 2k April in 
the 5° N. section was noted as being 25 to 50 percent immatures. Both 
Howland and Christmas colonies had recently fledged young. 
I do not believe that actively breeding Howland Island birds forage 
up into the 5° zone. 
Birds in the 12° N. belt are likely from Sand/johnston and the 
Hawaiians, but I doubt that the Palmyra birds contribute much. 
Concentrated collecting in the two zones would undoubtedly yield 
some informative band recoveries. 
Crested Tern # Obs. - 9 + 
Thalasseus bergii 
3iras were frequent in proximity to Viti Leva and irregularly seen 
in the Koro Sea. Outside of the Fiji area no birds were recorded at 
sea nor were any observed in the offshore waters of Christmas Island, a 
breeding station. 
Blue-gray Noddy # Obs. - 52 
Procelsterna cerulea 
Several birds were seen near Washington Island which I take as all 
bun conclusive evidence of breeding. A few birds were seen near Chrisunas 
Island and several were noted in the Phoenix group;' both being breeding 
locations. • j 
I 
/ 
/ 
