Effects of I>1>T in, bald < agU -. Studies on the 

 effects of pesticides on eagles were continued in 

 1963, both by experimental studies and by deter- 

 mination of DDT residues in eagles found dead 

 in various places in North America. 



The 1961-62 feeding experiments in Alaska 

 demonstrated that eagles can be killed by DDT, 

 and indicated that a median lethal dose within 

 100 days is about Kit) p. p.m. in the diet. Residue 

 analyses of those birds show that they are variable 

 in their accumulation of pesticides. 



In 1962 -63, 16 eagles were captured along the 

 Chilkat River, Alaska, where large numbers con- 

 gregate to feed on spawning salmon. The birds 

 were kept at the Experimental Fur Station, 

 Petersburg, Alaska, and had continuous access to 

 water and to the ground. 



The feeding experiments were designed to show 

 residue gain and loss rates in wild birds. Results 

 indicated that eagles accumulated residues when 



fed pesticide-contaminated food and eliminated 

 them when fed clean food. 



The Patuxent Center has received 58 bald eagles 

 found dead or incapacitated in 20 States and 2 

 Provinces. Autopsies showed that at least 16 

 (and possibly 24) had been shot : 3 were sick; the 

 others died of unknown causes. Residue analyses 

 have been made of at least some organs of 56 of 

 the eagles. All but one, a bird from Alaska, con- 

 tained detectable DDT residues. In addition, five 

 bald eagle eggs from three unsuccessful nests in 

 Xew Jersey and Missouri contained 24.3, 11.4, 36.9, 

 1.1, and 5.6 p.p.m. of DDT. 



These findings show that eagles in the wild have 

 access to, and ingest, substantial quantities of 

 DDT. This strongly suggests that a high pro- 

 portion of bald eagles carry DDT and its metab- 

 olites in their tissues. The existence of residues, 

 however, does not foretell what effects, if any, 

 they may have, either on adults or on eggs. 



An immature bald eagle being examined for evidence of disease and parasites. Tissue specimens will be subjected to 

 pesticide analysis. The bird, found weak and sick on the Chippewa National Forest, Minnesota, was sent to the 

 Patuxent Center for examination. (Photo by F. C. Schmid) 



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