ハイタカ
The Eurasian sparrowhawk population in Europe crashed in the second half of the 20th century. The decline coincided with the introduction of cyclodiene insecticides – aldrin, dieldrin and heptachlor – used as seed dressings in agriculture in 1956. The chemicals accumulated in the bodies of grain-eating birds and had two effects on top predators like the Eurasian sparrowhawk and peregrine falcon: the shells of eggs they laid were too thin, causing them to break during incubation; and birds were poisoned by lethal concentrations of the insecticides. Sub-lethal effects of these substances include irritability, convulsions and disorientation. In west Germany, around 80% of nests before the 1950s produced young, but only 54% were successful in the 1960s and '70s.