DDE-induced eggshell-thinning in the American kestrel: a comparison of the field situation and laboratory results.
Residues of DDE in kestrel eggs collected near Ithaca, New York, averaged 35, 42, 33 and 37 p.p.m. in 1969, 1970, 1971 and 1972, respectively. Based on Ratcliffe's Index [cf. RAE/A 58, 3735], eggshells of the local population were on average 10% thinner than pre-DDT eggshells. A dose-response relationship is established for dietary DDE and eggshell-thinning in a captive kestrel population. Statistical analysis revealed that the correlative relationship between DDE in the egg and eggshell-thinning is the same for both captive experimental birds and the wild population. Evidence on the use of organochlorines, on eggshell-thinning and on the decline of several populations of North America raptors indicates a causal relationship between the ingestion of prey highly contaminated with DDE and eggshell-thinning and eggshell breakage. The breeding failure that follows and the subsequent population decline of several raptor species proceeds in a straightforward, logical and well-documented sequence.