Breeding success and organo-chlorine residues in golden eagles in west Scotland.
Dieldrin was banned from use in sheep dips in January 1966. The proportion of golden eagle eyries in western Scotland that produced young increased from 31% in the period 1963-65 to 69% in the period 1966-68. Concurrently, the dieldrin level in eagles' eggs fell from 0.86 ppm to 0.34 ppm, respectively. Eagles in eastern Scotland, where dieldrin levels in eggs are very low, consistently maintained a high breeding success rate between 1963 and 1968. No environmental changes are correlated with the improved breeding success rate in western Scotland.