Potential of Using Movement Data to Predict Lead Exposure in California Condors

Lead poisoning still remains the number one cause of death for the Critically Endangered California Condor. Testing individual condors for blood lead levels and treating those with lead exposure are crucial pieces of the California Condor Recovery Program. However, regularly trapping and testing each condor is time- and resource-intensive for field teams and can be stressful for the birds. Alternative, less invasive methods for tracking lead exposure would benefit biologists and condors alike. 

One method that has been proposed is using GPS tracking data to identify patterns of movement consistent with lead exposure. A team of Peregrine Fund scientists collaborated with the Konrad Lorenz Research Center for Behavior and Cognition in Austria to examine whether this potential method of tracking lead exposure is a viable option. They used pre-testing GPS tracking data and lead testing results from individuals in the Arizona–Utah condor population to determine if lead-exposed condors had moved differently across the landscape when compared to those with background levels (i.e., no traces of recent lead exposure).

The results, published in Ecotoxicology, reveal that condors exposed to lead tended to have larger ranges than the background-level birds, and range was larger for older individuals. This is consistent with what our teams have noted, with juvenile birds remaining close to release sites and taking advantage of supplemental (lead-free) food provided by our teams. As the birds mature, they are more likely to venture farther away from the safe, supplemental food source to access other food sources, often contaminated with lead. The researchers also found that lead-exposed condors had more overlap in their ranges when compared with background-level birds, indicating the lead-exposed birds may be consuming the same contaminated carcasses. 

The findings of this research indicate that there may be a potential to use movement data to detect California Condors with lead exposure. Further research is needed to explore this minimally invasive detection method in greater detail and investigate how it may provide early warnings of lead exposure.