“s + owen - 38 - only a limited time, and which feed for the most part on crustacea along ‘the beaches. The northern groupof birds consisted entirely of terns. Because of their limited migrational tendencies, the terns provide a noose - more representative sample for the determination of continued uptake and In the collections prior to October 1955 the following organs were pro- _ cessed: skin, muscle, bone, lung, liver, kidney, ileum, and thyroid. In the‘October collections only muscle, bone and liver were takenin an effort to reduce the total number of samples. The average specific activities of muscle, bone and liver of Rongelap ee and Ailinginae birds are given in Table 11. At the time of the October col- oo 5 leetions the radioactivity levels in the three tissues of the north Rongelap Be terns were approaching a common value, with the most radioactive tissue “(iver) having an activity only 2, 45 times that of the least active tissue *(bone). 3.67. In the Enibuk terns the ratio of highest radioactivity to lowest was The differences between the highest and lowest levels of activity ww Ge : haveconsistently declined sincethe first collections in March 1954. Me - The March 26, 1954 - 1; 8.5 July 16, 1954 ol: 5. 6 December 8, 1954-1: 5.4 January 28-30, 1955 - i:3.1 Octoher 21, 1955 - 1: 2.5 ue UNIVER TY UNTV. OF > SS a FM BUY RIP Rey dfi ‘pirds® although in some respects the two groups are similar. Peers “metabolism of radioactive materials at Rongelap Atoll than do the shore