Apnl 1965 



May 1965 



O' Winterers 

 i? Migrants 

 ^ Unidentified 

 Q> Breeders 



Figure 26c. — Relative composition of avifauna by 

 species group, April-June 1965. Numbers in 

 parentheses in each sector indicate the per- 

 centages of total birds in each category. 



Direct Migrants. 



Mottled Petrel 

 Pale-footed Shearwater 

 Sooty Shearwater 

 Slender-billed Shearwater 

 Golden Plover 

 Red Phalarope 

 Long-tailed Jaeger 

 Arctic Tern 



Breeding birds dominated in all months ex- 

 cept March and November 1964. In January and 

 February 1965, breeding birds exceeded 90 

 percent, even though total population during 

 these 2 months was low. The height of the 

 breeding season in the Hawaiian area is indi- 

 cated both by the large total population and by 

 the high percentage of breeding birds during 

 May 1964 (89 percent) and May 1965 (86 percent). 

 Migrants were relatively numerous in the area 

 only in March and April and from September 

 through November. Wintering birds were well 

 represented from June through December even 

 though two of the wintering species, Leach's 

 Storm Petrel and Pomarine Jaeger, were breed- 

 ing in Alaska during at least the first 3 months 

 of this period. The greatest representation of 

 birds wintering in the area (36 percent) came in 

 October 1964 when both Juan Fernandez Petrels 

 and Black-winged Petrels, the two most abun- 

 dant wintering forms, were at peak numbers 

 just before their return to the Southern Hemi- 

 sphere for the beginning of their breeding 

 season. 



Distance from Land 



Red-tailed Tropicbird 

 Blue-faced Booby 

 Brown Booby 

 Red-footed Booby 

 Great Frigatebird 

 Brown Noddy 

 Black Noddy 

 Sooty Tern 

 White Tern 



Resident in Nonbreeding Season. 



Juan Fernandez Petrel 

 White-necked Petrel 

 Black-winged Petrel 

 Kermadec Petrel 

 Leach's Storm Petrel 

 Pomarine Jaeger 



Birds of species that occurred in the study 

 area in significant numbers were tallied, ac- 

 cording to the distance from nearest land at 

 the time of observation, in increments of 50 

 and 100 miles from nearest land. Figure 27 

 shows these distance-from-nearest-land iso- 

 pleths superimposed on the nominal cruise 

 track. The miles traveled while observations 

 were underway were divided into the numbers 

 of birds observed to yield a birds-per-mile 

 figure. Table 5 illustrates the abundance of 

 the more common species in relation to miles 

 from- nearest land. 



Five patterns of distribution were noted: 



1. Species that were observed predominantly 

 within 50 miles of land: 



66 



