Science  29 Jun 2012:
Vol. 336, Issue 6089, pp. 1626

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  1. Condors Suffer Lead Poisoning

    A captive breeding program for the endangered California condor (Gymnogyps californianus) has increased the condors' numbers to almost 400. But a study published online 25 June in the Proceedings of the National Academy of Sciences finds that condors are still threatened by lead poisoning from scavenging the carcasses of animals shot with lead-based ammunition.

    Condors feed on the remains of large animals—the most likely to have been shot. High levels of lead can shut down the condors' digestive system, causing the birds to starve. Research toxicologist Myra Finkelstein of the University of California, Santa Cruz, and colleagues checked more than 1000 blood samples from 150 condors between 1997 and 2010. About 70% of birds had signs of lead exposure; an analysis of lead isotopic ratios verified that bullets were the source.

    The success of captive breeding programs may mask the danger of lead, Finkelstein says: Condors are caught twice a year, tested for lead, treated, and released. This will keep bird populations stable—but the researchers' models suggest that unless the lead ammunition is eliminated, the birds won't survive on their own.