So scientists have come up with a shocking idea.Tall poles,placed in large training areas,teach the birds to stay clear of electrical lines by giving them a painful but undeadly electric shock.Before the training was introduced,66% of set-free birds died of electrocution.This has now dropped to 18%.
Lead poisoning has proved more difficult to deal with.When condors eat dead bodies of other animals containing lead,they absorb large quantities of lead.This affects their nervous systems and ability to produce baby birds,and can lead to kidney(肾) failure and death.So condors with high levels of lead are sent to Los Angeles Zoo,where they are treated with calcium EDTA,a chemical that removes lead from the blood over several days.This work is starting to pay off.The annual death rate for adult condors has dropped from 38% in 2000 to 5.4% in 2011.
Rideout?s team thinks that the California condors? average survival time in the wild is now just under eight years.“Although these measures are not effective forever,they are vital for now,” he says.“They are truly good birds that are worth every effort we put into recovering them.”
【语篇导读】 本文是一篇说明文。在二十世纪八十年代,加利福尼亚的秃鹫的数量在减少,原因是由于高压电线和铅中毒威胁着它们。为此科学家们采取了一系列的措施保护它们,并且取得了一定的成效。
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