The pesticide DDT has been implicated in the decline of Bald Eagle populations throughout North America. As a result of the link between thin eggshells and DDT concentrations found in eggs, DDT was banned in the U.S.A. on 31 December 1972. Below are data collected for the number of young counted before and after the ban of DDT.
| Table 5. The effect of DDT on Bald Eagles. (Adapted from Mooney, D. D. and R. J. Swift. 1999. A course in mathematical modeling. The Mathematical Association of America. ISBN 0-88385-712-X.) | |
| Year | Young per area |
| 1966 | 1.26 |
| 1967 | 0.73 |
| 1968 | 0.89 |
| 1969 | 0.84 |
| 1970 | 0.54 |
| 1971 | 0.60 |
| 1972 | 0.54 |
| 1973 | 0.78 |
| 1974 | 0.46 |
| 1975 | 0.77 |
| 1976 | 0.86 |
| 1977 | 0.96 |
| 1978 | 0.82 |
| 1979 | 0.98 |
| 1980 | 1.12 |
| 1981 | 0.82 |
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