stations are plotted against distance collected from Ground Zero (Fig. 4.8), the effect of the site of collection upon the amount cf activity within the organs or tissues is apparent. Meter readings were taken at each collecting site with a Juno ionization type instrument at the time the collections were made. These values for Runit, Aaraanbiru, and Rigili are given in Appendix G. On the basis of the meter readings, the activity levels in the terns from Runit and Rigili should be similar, but those of the terns from Aaraanbiru should be higher. This was not 0 found to be true, however (Fig. 4.8). At Rigili, downwind from Groind Zero, there were higher average levels of activity in the terns than at either Runit or Aaraanbiru, in which the levels were almost equal (Table 4.17b). The terns taken at Runit may have flown from -- neighboring northerly islands since, although singed, they were able to fly. The birds taken at Rigili, however, probably did not fly from islands closer to the target area because all the birds observed during the postshot collections at Rigili were singed or ill and not inclined to fly. They would walk away or flutter with effort from the beach to the water when anyone camenear. 4.7.6 Analysis by Feeding Habit The shore birds and rats have similar feeding habits; both subsist mainly on insects, seeds, and grasses; therefore a comparison of average levels of activity in diverse forms with similar feeding habits can be made. The results are given in Table 4.18. Table 4.18-—-RADIOACTIVITYIN RATS AND SHORE BIRDS COMPARED BY FEEDING HABITS Rats (Biijirt) — Shore birds (Rojoa) - Ratio of activity Organ or tissue n Activity, d/m/g (x 1000) n Activity, d/m/g (x 1000) of shore birds to rats 7 - Skin Muscle Bone Liver Digestive 6 6 6 6 12 9.2 0.94 17 1.9 8.1 2 2 2 2 6 19 0.63 7.6 2.5 57 2.06 0.67 0.45 1.32 7.04 : 6 1.0 2 0.86 0.87 tract Lung Only in the activity of the digestive tract do the two forms differ ty more than a factor of 3; also the differences are not consistently in favor of either of the forms. Differences in activity levels between birds of different feeding habits were found. Average values for the shore birds of the Rojoa-Aaraanbiru area and those for the terns in the Aaraanbiru area are given in Table 4.19. Shore birds and rats appear to be morealike in relation to uptake of radioactive materials than do the shore birds and terns. It appears likely, however, that the shore birds and rats are different regarding the retention of radioactive materials within the different organs and that the differences between the terns and shore birds were caused by differences in feeding habits. Although variations within the tissue or organ samples of birds were great enough to preclude analyses of the radioactive disintegration rates by organ, a few conclusions can 56 UNCLASSIFIED > ~--