. _— (’ ! I ● —.—. . . —.— —-—life cycle of the Sooty T=- has been the subject of intensive study in the central Pacific. me first evidence that breeding a~ti~ty is about to take place is ‘& presence at night of increas~:~v large numbers of Sooty Terns, szirlhg over the island in a loose s~”iral. . A highly social species like the Sooty Tern requires the ~rc:er s3cial stimulus in order to c=mce breeding, and in this case tie social stimulus is provided by the dense swirls of birds ~ELF ~d over their intended breedislaid. At last, when all conditions appear to be right, the first birds touch down for a short.time d’aring We can only speculate the night. on what the “proper” conditions are. They probably include the assurance of a continued food supply at sea f~yi~ time from the ~it~ a d~yrs 3$3 island, eno’ugh bzac ground available for nesting, and sufficient numbers of Sooty Terns swirling together to satisfy the social stimulus requirements of the colony. Gradually the numbers of birds touching down increases from night to night and the length of time they spend on the ground increaaes too. Finally, scme stay through the day as well, snd im.mediateUy eggs are leicl. Tne thereafter parents take turns incubating their egg which they cmer with their dlstibreast on a simple, shal~5W They shaped scrape in the sand. are surrounded by other Sooty Terns, all incubating their eggs. Their nearest neighbors are usually only In many colonies the a ioot away. available nesting space is utilized Frigatebirds and on three levels. boobies roost in the bushes, sooty Terna on the ground, and shearwaters and petrels occupy burrows under the ground. —