relation to their breeding cycles. A monthly 

 summary gives the temporal sequence of 

 changes in abundance and distribution ot the 

 most important components of the avifauna. 



Family Summary 



Species from 12 families, the first 3 from the 

 order Procellariiformes, the next 3 from Pele- 

 caniformes, the next 5 from Charadriiformes, 

 and the last 1 from Columbiformes, were re- 

 corded in the study area. All but the last are 

 normally considered sea birds or shore birds; 

 the last is a land-based group and the occur- 

 rence of a bird of this order at sea was acci- 

 dental. 



1. Diomedeidae 



The albatrosses were represented by 

 three species, Black-footed and Laysan Alba- 

 tross, both of which breed during the winter 

 on the leeward Hawaiian chain, and the Black- 

 browed Albatross, a South Pacific breeder 

 from south of New Zealand, which was tenta- 

 tively identified for the first time in the area. 

 The albatrosses were conspicuous members 

 of the avifauna in the study area during the 

 winter breeding season when they followed 

 the ship readily. Although almost always 

 restricted to the northern half of the cruise 

 area, birds occasionally followed the ship 

 south of lat. 18° N., and on one occasion south 

 of lat. 11° N. 



2. Procellariidae 



The shearwaters and gadfly petrels were 

 represented by 21 species or field-recogniz- 

 able subspecies. One is a rare straggler 

 from the North Pacific, six breed on the 

 Hawaiian Islands and are absent in the non- 

 breeding season, seven breed in the South 

 Pacific and winter in the study area, and 

 seven migrate through the study area between 

 their South Pacific breeding areas and win- 

 tering grounds north of the study area. All 

 members of this family recorded are char- 

 acterized by long migrations and by periods 

 of abundance followed by periods of scarcity 

 or absence. Although the shearwaters and 

 gadfly petrels are less conspicuous than the 

 albatrosses because they are smaller and 

 usually do not follow ships, the family ranked 

 second in total numbers seen and in some 

 months ranked first. 



3. Hydrobatidae 



Only two species of storm petrels were iden- 

 tified with certainty. Leach's Storm Petrel, the 

 most abundant, migrates south in the winter in 

 large numbers from North Pacific breeding 

 stations. Fork-tailed Petrel is a rare winter 

 straggler from the North Pacific. Two others 

 probably occur in the area, but, because of the 

 possibility of confusion with other species, they 

 must be considered hypothetical. 



4. Phaethontidae 



Tropicbirds were represented by two 

 species, both of which were observed com- 

 monly in all months. They are attracted 

 frequently to ships. Because of the even 

 distribution of Red-tailed Tropicbirds, their 

 islands of origin are in doubt. The White- 

 tailed Tropicbirds probably all came from 

 the main Hawaiian islands. 



5. Sulidae 



The distribution of two of the three species 

 of boobies in the study area was limited es- 

 sentially to the area within 50 miles (92.7 

 km.) of the main Hawaiian islands. The third 

 species occurred primarily in the southern 

 half of the study area--a circumstance which 

 indicates it was probably from the Line or 

 Phoenix Islands. 



6. Fregatidae 



Great Frigatebirds, the only frigatebirds 

 observed, were seen in all months, mainly 

 within 300 miles (556 km.) of the Hawaiian 

 Islands. 



7. Charadriidae 



One member of this family, the Golden 

 Plover, was common in the fall during mi- 

 gration to Pacific islands from Siberia or 

 Alaska. 



8. Scolopacidae 



Although all four sandpiper species ob- 

 served were common on nearby Pacific is- 

 lands, each was seen at sea only once. 



9. Phalaropodidae 



One phalarope species, probably the Red 

 Phalarope, was seen commonly in the spring 

 migrating north to the Arctic. 



