waters of the study area for their food supply. 

 I have set up for analysis the following seven 

 categories of birds, based on origin and mode 

 of utilization of study area: birds breeding in 

 the main Hawaiian islands; birds breeding in 

 the leeward Hawaiian islands; birds breeding 

 in the South Pacific and wintering in the study 

 area; birds breeding in the South Pacific and 

 migrating through the study area; birds breed- 

 ing in the North Pacific and wintering in the 

 study area; birds breeding in the North Pacific 

 and migrating through the study area; and birds 

 recorded in the study area only rarely. 



1. Birds breeding in the main Hawaiian 

 islands. 



Dark-rumped Petrel 



Bulwer's Petrel 



Wedge-tailed Shearwater (light-phase) 



Newell's Shearwater 



White-tailed Tropicbird 



Brown Booby 



Red-footed Booby 



Sooty Tern 



Brown Noddy 



Black Noddy 



Most of these species breed in the spring and 

 summer. Two possible exceptions are the 

 White-tailed Tropicbirds and Black Noddies; 

 their breeding cycles in the main Hawaiian 

 islands have not been accurately described, 

 although there is some evidence that their 

 breeding seasons are long. The petrels, shear- 

 waters, and Sooty Terns migrate annually and 

 are absent, or scarce, during the fall and early 

 winter in the study area within 100 miles of 

 their breeding grounds. The boobies and nod- 

 dies are land-oriented and remain near the 

 breeding islands all year, foraging out to sea 

 usually no farther than 100 miles. 



Probably most birds of these species ob- 

 served in spring and summer in the study area 

 within 100 miles of the main Hawaiian islands 

 originate on those islands; their densities with- 

 in this distance are consonant with estimates of 

 populations breeding on these islands. 



Several other species with very small popu- 

 lations in the main Hawaiian islands (Christmas 

 Shearwater, Red-tailed Tropicbird, Blue-faced 

 Booby, White Tern, Gray-backed Tern, Blue- 

 gray Noddy) were observed in the study area. 

 The first four were observed with far greater 

 regularity and in greater numbers than could 

 be expected from the main Hawaiian popula- 

 tions. The Gray-backed Tern and Blue-gray 



Noddy were seen on only one occasion each; 

 they are considered rare in the study area and 

 probably originate on islets off the main Hawai- 

 ian islands that support small populations of 

 the species. 



2. Birds breeding in the leeward Hawaiian 

 islands. 



Black-footed Albatross 



Laysan Albatross 



Bonin Petrel 



Bulwer's Petrel 



Wedge-tailed Shearwater (light-phase) 



Christmas Shearwater 



Red-tailed Tropicbird 



Blue-faced Booby 



Brown Booby 



Red-footed Booby 



Great Frigatebird 



Sooty Tern 



White Tern 



Only the albatrosses, Red-tailed Tropicbird, 

 Great Frigatebird, and White Tern contribute 

 appreciably to the avifauna of the study area. 

 To this group might be added Bulwer's Petrel 

 and Christmas Shearwater, which may enter 

 the study area from the leeward Hawaiian chain, 

 but probably not frequently or regularly. The 

 remaining species more likely originate on the 

 main Hawaiian islands, especially those ob- 

 served within 100 miles of land, although indi- 

 viduals from the Leewards undoubtedly enter 

 the area on occasion. The occurrence of light- 

 phase Wedge-tailed Shearwaters and Sooty Terns 

 in the southern half of the study area could as 

 well be attributed to migration from the Lee- 

 wards, from the main Hawaiian islands, or from 

 other Pacific islands. 



Bonin Petrel is an uncommon visitor from 

 the Leewards to the northern half of the study 

 area. 



3. Birds breeding in the South Pacific and 

 wintering in the study area. 



Juan Fernandez Petrel 



White-necked Petrel 



Tahiti or Phoenix Petrel 



Black-winged Petrel 



Kermadec Petrel 



Herald Petrel 



Bulwer's Petrel 



Wedge-tailed Shearwater (dark-phase) 



Christmas Shearwater 



Red-tailed Tropicbird 



Blue-faced Booby 



63 



