BIRDS IN FLOCKS 



MVARCH 1964 



APRIL 1964 



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Figure 35a. — Distribution of birds in flocks, March-June 1964. 



the main Hawaiian islands where they were 

 fairly abundant. Juan Fernandez Petrels and 

 Black-winged Petrels were found most fre- 

 quently in flocks in the southern end of the 

 study area. 



The following species were also observed in 

 mixed or pure flocks but their numbers never 

 accounted for more than 1 percent of total 

 numbers of birds in flocks for any one month: 



Kermadec Petrel 



Phoenix Petrel 



Bulwer's Petrel 



Pink-footed Shearwater 



Newell's Shearwater 



Sooty Shearwater 



Christmas Shearwater 



Leach's Storm Petrel 



Red-tailed Tropicbird 



White-tailed Tropicbird 



Great Frigatebird 



Pomarine Jaeger 



Long-tailed Jaeger 



Skua 



Blue-gray Noddy 



Black Noddy 



White Tern 



Flock participation . — Sooty Terns partici- 

 pated in 76.0 percent of all flocks--consider- 

 ablymore than the next closest species, Wedge- 

 tailed Shearwater (39.0 percent, table 10). No 

 other species participated in more than one- 

 quarter of all flocks. Wedge-tailed Shearwaters 

 were the second-most-abundant birds in flocks, 

 although they had a lower tendency to flock than 

 did the Sooty Tern. Their presence most of the 

 year in the area increased their relative flock 

 participation over Brown Noddies, which were 

 restricted geographically, and Juan Fernandez 



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