Organo-chlorineA member of a group of chemicals used as pesticides in agriculture (for example DDT, BHC, aldrin, dieldrin and heptachlor) and also used in industry (polychlorinated-biphenyls or PCBs). The latter enter the environment via effluents from factories. Birds can ingest toxic chemical residues by eating plants which have been treated with pesticides or by eating animals which have been contaminated by eating treated plants. Large doses can be lethal, while 'sub-lethal' quantities can cause various ill effects, notably reduction in breeding success through such problems as eggshell thinning. These chemicals are particularly dangerous to birds which are at the top end of a food chain and some species of raptor, for example the Peregrine Falco peregrinus, have suffered very serious population declines as a result.
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From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver