This article describes the use of feather testing to monitor lead exposure in California Condors. Since blood lead levels change quickly, while feathers retain increment-specific indications of lead exposure across their entire 2-4 month growth period, feather analysis greatly enhances the ability of managers to monitor lead exposure in predatory avian species. Seven case studies are described. The birds were tested due to illness, during routine monitoring, or after they scavenged carcasses that contained lead ammunition. One of the case studies provides the first documentation of acute lead exposure due to lead ammunition.

[Abstract excerpted from original source.]

“Lead poisoning is a primary factor impeding the survival and recovery of the critically endangered California Condor (Gymnogyps californianus). However, the frequency and magnitude of lead exposure in condors is not well-known in part because most blood lead monitoring occurs biannually, and biannual blood samples capture only 10% of a bird’s annual exposure history. We investigated the use of growing feathers from free-flying condors in California to establish a bird’s lead exposure history. We show that lead concentration and stable lead isotopic composition analyses of sequential feather sections and concurrently collected blood samples provided a comprehensive history of lead exposure over the 2−4 month period of feather growth. Feather analyses identified exposure events not evident from blood monitoring efforts, and by fitting an empirically derived timeline to actively growing feathers, we were able to estimate the time frame for specific lead exposure events. Our results demonstrate the utility of using sequentially sampled feathers to reconstruct lead exposure history. Since exposure risk in individuals is one determinant of population health, our findings should increase the understanding of population-level effects from lead poisoning in condors; this information may also be helpful for other avian species potentially impacted by lead poisoning.”

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