present in or on most samples before treatment. 

 On vegetation tlie highest residues were found on 

 the day of application, and amounts decreased 

 with time. Residues in soil increased only slightly 

 after treatment, but amounts of DDT in litter 

 covering the forest floor increased greatly after 

 treatment and remained high after .3 months' 

 elapsed time. 



Residues in insects collected in drop cloths were 

 strikingly high. Results .'showed that they had 

 accumulated large quantities of DDT before dy- 

 ing, thereby becoming a highly concentrated 

 source of DDT contamination to insectivorous ani- 

 mals. After 1 month, live insects still contained 

 residues of DDT, but in much smaller quantities. 

 Amounts found in insects on the day of applica- 

 tion were 206.2 japm ; on the first and second days 

 after treatment, 83.7 ppm; and 1 month after 

 treatment, 1.9 ppm. 



Songbirds and white-footed mice were collected 

 to depict the residues accumulated in wildlife. All 

 birds contained residues before treatment, but no 

 DDT was found in mice from pretreatment sam- 

 ples. Amounts of DDT increased in birds after 

 DDT applications. 



In robins, residue averages after 3 months were 

 less than before treatment (0.4 ppm vs. 0.2 ppm). 

 Wright's flycatchers and western tanagers had 

 migrated from the area before the 3-month sample 

 was taken, but increased levels of DDT residues 

 at the 6-week check were equal to those on the 

 treatment day. Juncos and chickadees, many of 

 which reside during winter in the treated area, 

 appeared to accumulate residues, and residue 

 levels were greatest 3 months after treatment (6.0 

 and 11.7 ppm, respectively). DDT appeared in 

 white- footed mice after applications were made 

 to the forest, but levels remained low through the 

 first 3 months following treatment (0.1 i)pm) . 



Contamination removed from Rocky Mountain 

 Arsenal lake.i. — The Army has removed aldrin- 

 and dieldrin-contaminated muds from tiie bottoms 

 of the three industrial lakes at the Rocky Moun- 

 tain Arsenal. The problem resulted from occa- 

 sional e/^uipment failures in a portion of the 

 arsenal plant leased for the manufacture of agri- 

 cultural insecticides. The lakes, from which 

 water was circulated for cooling purposes, had 

 been responsible for the death of several thousand 

 waterfowl annually over a period of 10 to I.t years. 

 The Denver Center prepared a bottom-sampling 

 plan, together with analj'tical specifications for 



the determination of aldrin and dieldrin, and 

 supervised the collecton of approximately 800 

 samples, most of which were analyzed under con- 

 tract by a private laboratory'. 



Following completion of the analytical work, the 

 lakes were drained and 4 to 6 inches of soil re- 

 moved from the bottoms. Areas of high concen- 

 tration were resampled and 6 to 18 additional 

 inches of soil were removed. To prevent recon- 

 tamination, a closed-system cfx)ling installation 

 was completed and is now functioning. 



Effects of pesticides on birds of prey. — Wide- 

 spread declines in populations of birds at the top 

 of the ecological food chain have been reported 

 from a number of locations. These birds live in 

 environments subject to many changes, including 

 increasing pollution of all kinds. Pesticides are 

 now universally foimd in living animals. Certain 

 characteristics of such compounds as DDT and 

 dieldrin are of much concern because of their ten- 

 dency to accumulate in animal tissues, aflFecting the 

 animals themselves and their progeny. 



Relations between DDT residues in osprey eggs 

 and osprey reproductive success in the wild were 

 studied on the Connecticut and Potomac Rivers 

 in cooperations with Dr. Peter L. Ames of Yale 

 University during the summers of 1963 and 1964. 

 Tlie Connecticut colony was chosen because it was 

 known to be declining and to have very poor 

 reproductive success. The Marj'land colony was 

 chosen for contrast, for it was known to be 

 flourishing. 



Tlie plan involved taking one egg from each of 

 a number of nests in each colony for pesticide 

 analysis, and then determining nest success for 

 both areas and correlating with residues in eggs. 

 Reproductive success in the two areas differed 

 sharply, as shown in the following tabulation : 



< Based on number of nests successfully fledging young. 

 > Numbers in parentheses show eggs remaining after sample eggs were 

 removed. 



Although there was considerable overlap in 

 range, DDT residues averaged higher in eggs from 

 the Connecticut colony than in eggs from the 

 Potomac (6.5 vs. 3.4 ppm). 



45 



