November 13. Over 96 percent of the birds 

 seen in the area were recorded on these 5 days. 

 Thereafter only stragglers were observed. 



This species was difficult to distinguish from 

 the similar Sooty Shearwater when only small 

 numbers of one or both species were present. 

 Thus, although a few of each species may have 

 been identified as the other, the totals in the 

 monthly abundance table for this species would 

 not be altered significantly. 



Owing to the short duration of the migration, 

 a distribution analysis would have little mean- 

 ing. A second migration wave may well have 

 occurred when the ship was in port between 

 cruises. 



If a northward migration had taken place 

 through the area in the spring we would have 

 seen more than one bird, even if there had been 

 a peak of migration as sharp as the fall peak. 



POBSP personnel have collected specimens 

 at comparable latitudes west of the study area. 



breeding in the Line or Phoenix groups or else- 

 where to the south. 



No birds were seen in the northern half of 

 the area in January, February, or March, al- 

 though birds first appear on their breeding 

 grounds in the leeward Hawaiian chain in early 

 March (Richardson, 1957). 



Christmas Shearwater 

 Puffinus nativitatls Streets 



Christmas Shearwaters were evidently pres- 

 ent in the area in most, perhaps all, months of 

 the study. The low numbers observed prevent 

 any precise placement of population peaks. 



Distribution : The fact that no Christmas Shear- 

 waters were seen between long. 17° and 21° N. 

 (fig. 13) may be due to chance. It might also be 

 explained by the presence in the study area of 

 two populations of this species--one northern, 

 presumably breeding along the leeward Hawaiian 

 chain, and the other southern, presumably 



i 1 bird 



Figure 13. — Distribution of Christmas Shearwater. 



35 



