Lead poisoning continues to be a significant threat to scavenging raptor species, such as vultures, bald eagles, and golden eagles. Although understood to be prevalent, the magnitude and degree of lead poisoning lack sufficient quantifying data across the field.
Measuring the concentration of lead in birds’ blood is how The Raptor Center’s (TRC) veterinarians determine if a bird may be suffering from lead poisoning. However, blood collection only represents a single point in time in birds’ exposure histories because lead moves relatively quickly in and out of the blood. Measuring blood lead levels, which TRC does for every eagle and vulture on admission, only offers an indication of the lead the bird has been exposed to very recently.
Alternatively, lead levels can also be measured in feathers, and TRC is collaborating on research with leading experts on the impact of lead on wild raptor populations. Together with Drs. Myra Finkelstein, University of California Santa Cruz, and Todd Katzner, U.S. Geological Survey, lead levels in bald eagle feathers are being measured to give a better understanding of the amount of lead that an eagle has been exposed to over a longer period of time.
As raptors lose feathers during their natural molting cycles, blood supplies the nutrients needed to grow new feathers. Whatever level of lead is circulating in the blood during the time of feather growth gets deposited into the keratin (protein) of the feather. By measuring the level of lead in the feather from base to tip, we can get an idea of what exposure to lead the bird experienced over the length of the feather’s development. Because birds molt their feathers in phases, acquiring multiple feather samples provides a broader idea of what levels of lead this bird has seen over time.
Birds that come into rehabilitation for treatment of their injuries/illnesses can help TRC and its partners learn this information while they are here for treatment. Overall, studying lead levels in feathers will advance the ability to evaluate cumulative lead exposure rates which can be related to the negative health effects lead has on bald eagles and other avian species worldwide.
