since the light phase Red-feet had dark tails (subspecies websteri) and the Blue-faces had orange-colored bills (subspecies granti). Frigatebird (Fregata) Adult female Magnificent Frigatebirds are easily distinguished from female Greats by the color of the throat -- black in the Magnificent, and grey in the Great. It is just as easy to distinguish between the adult males of these species at close range, for the male Magnificent has a light (blue) colored bill while the male Great Frigate has a dark (black) bill. This character should work 99 percent of the time. However, a male Great that has just molted into the adult plumage may retain the light colored bill of the subadult for a while. Arctic Tern (Sterna paradisaea) In September Arctic Terns were commonly encountered far from land generally moving southeast, but at other times in feeding flocks. Even those traveling groups were seen feeding. Evidently the migration of this species is leisurely. Sooty Tern (Sterna fuscata) Sooty Terns were generally uncommon over the area (see FIGURE 16) being seen in numbers larger than a hundred on only four days. Two populations were evidently present in the area - a pre-nesting one and a post-nesting one. Near the Galapagos the flocks observed contained no young birds and the adults were in fresh plumage indicating the start of nesting cycle in this island group. On two other days when fairly large numbers of Sooties were seen immatures were present. These birds are very likely from Clipperton Island. On 2 September I saw a flock of eight adult Sooties sitting on the water. I have never before seen them on the water when immatures were not present also.