- 39 decay of individual samples of algae and by the radiochemical determinations which showed that in January 1955 a large fraction of the total radioactivity in the algae Caulerpa and Halimeda was due to Ce144 and that none of it was due to Cs 137 » which contributed most of the activity in land plants. Birds Birds were collected at four islands of Rongelap and Ailinginae Atolls during the latter part of October 1955. Terns were taken at Kabelle and Labaredj Islands in Rongelap Atoll and at Enibuk Island in Ailinginae Atoll and included three species: the fairy tern (Gygis alba), the noddy tern (Anous stolidus), and the black-naped tern (Sterna sumatrana). Terns were not available at Rongelap Island but two species of shore birds were collected at this site, including two ruddy turnstones (Arenaria interpres) and a reef heron (Demigretta sacra sacra). Specimens taken at Kabelle and Labaredj were treated as northern atoll birds and as one group. Those birds from the southern island of Rongelap as well as those from Enibuk Island ( Ailinginae Atoll) were considered to constitute a southern group 5 The birds of the southern group were further subdivided according to their feeding habits into (1) the terns, which forage in the area of a few islands within the atoll and feed principally on fish and (2) the shore birds, which are migratory, any one bird remaining in the area of an atoll for