MAY 1964 



JUNE 1964 





•> 



4 

 ^ 



»a^ 



• 1 bird 



• 5 birds 



• 25 birds 



• 100 birds 



• 400 birds 

 O 1000 birds 



%r 



••• 



^ 



«r & 



•l« 



^ 



V. 



Petrels, which 

 phenologically. 



were somewhat restricted 



Flocking tendency . --Among regularly obser- 

 ved species Sooty Terns exhibited the greatest 

 tendency to flock (table 11). Brown Noddies 

 tended to flock nearly as frequently, although 

 only around the main Hawaiian islands. Juan 

 Fernandez Petrels showed an almost equally 

 strong tendency in a more pelagic situation. Of 

 interest was the relatively high flocking tend- 

 ency of White Terns and Great Frigatebirds. 



These figures express, first of all, the feed- 

 ing patterns of the various species. Those 

 species or species groups which tend to feed in 

 a solitary manner--e.g.. Leach's Storm Petrel, 

 Bulwer's Petrel, and tropicbirds--demonstrate 

 a relatively low percentage of participation in 

 flocks, whereas those that feed collectively 

 show relatively high percentages. The selec- 



Table 10. — Participation by species or 

 species groups in 893 bird flocks in 

 the study area 



99 



