Environ. Sci. Technol. doi:10.1021/es903176w (2010)

Credit: ALL CANADA PHOTOS/ALAMY

Endangered California condors (Gymnogyps californianus; pictured) are heavily affected by lead poisoning, but current biannual testing detects only a fraction of their exposure.

Myra Finkelstein at the University of California, Santa Cruz, and her colleagues report that analysis of sequential segments of condor feathers can provide a history of lead exposure over the 2–4 months of feather growth.

By measuring lead concentration and isotope composition in feather and blood samples, the researchers identified lead-exposure events that would have been missed by blood monitoring alone. Their technique, they say, may also be applicable to other bird species.