California condors are one of those valuable species that clean up after the rest of us, eating flesh and even bone from carrion. Since their near-extinction 30 years ago, owing largely to lead poisoning from bullet fragments in the meat they consume, the population has been slowly rehabilitated. During the 1980s, the 22 condors remaining in the wild were relocated to zoos in a last attempt to increase their numbers. Efforts to reintroduce the condors to their natural habitat began in California in 1992 and in Arizona in 1996. To date, the population has risen to a total of 285 birds, including 69 birds in the wild in California, and condor pairs have started to produce nestlings. But a new problem, discovered by a team of scientists led by ornithologist Allan Mee, may threaten the condors' fragile reestablishment.
During a postdoctoral fellowship with the San Diego Zoo's Millennium Field Program in Conservation Science, Mee studied breeding attempts in the reintroduced condor population in the Los Padres National Forest in Southern California. The research, published in June in Bird Conservation International, finds that condors are bringing unprecedented amounts of human trash to their nestlings. "We had no idea that junk ingestion would be a problem," Mee says. But condor chicks are dying as a result.
Adult condors seem to be able to regurgitate most trash that they ingest. Not so for nestlings. The junk they eat lodges in their crops and gizzards, severely impairing the absorption of nutrients and, in some cases, causing life-threatening metal toxicity. Two of the nine Los Padres chicks that hatched between 2001 and 2005 died as...
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