to great heights, and therefore we probably missed some that were above the altitude of 

 the plane. 



Phalaropes are very small, but their pale coloration and flocking habits make them 

 more conspicuous than the storm-petrels. From the air the three species in winter 

 plumage are probably not separable. 



Laughing gulls are moderately conspicuous when alone, but their numbers are 

 probably underestimated when they occur in flocks with the more conspicuous royal 

 terns. 



The terns are the most abundant birds offshore and the group presents some 

 identification problems. 



Royal terns are large, pale, and have relatively broad wings set in the middle of 

 the body. They are very conspicuous, and with practice can be distinguished from the 

 rest of the terns even from 228-m altitude. 



Sandwich terns are smaller and more slender than royal terns, but larger than 

 common terns. They can occasionally be distinguished from the related species, but only 

 after experience. 



We identified as "common tern group" the species Forster's, common, roseate, and 

 Arctic terns. These four species are very similar and we consider them indistinguishable 

 from the air. They are pale and rather conspicuous, and as a group can be separated 

 rather easily from the other terns. 



Least terns are very small and normally occur close to shore. They can be 

 confused with the common group, but have shorter tails, relatively broader wings, and 

 "floppier" flight. 



"Pale terns" are unidentified royal, Sandwich, common group, or least terns. As 

 our experience increases, this category should become limited to those seen at great 

 distances or under other poor viewing conditions. 



"Dark terns" are unidentified sooty, bridled, and black terns. These species are 

 distinguishable in the field, but many are seen too poorly for positive identification. As a 

 group they are much less conspicuous than the pale terns, and the proportion sighted is 

 likely to be lower. 



Turtles 



Turtles presented distinct identification and detection problems in relation to 

 birds and mammals. They were usually sighted floating at the surface or swimming 

 immediately below the water surface. Consequently, they presented a low or nonexistent 

 profile except when viewed from above. Head width, carapace shape, body proportions, 

 and color were all useful criteria but depended upon adequate light, sufficient 

 observation time, and proper sighting angle. Turtles, like some birds, were rarely seen at 

 a distance. 



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