California condors face rising lead poisoning despite conservation progress

California condors were meant to become one of conservation’s most remarkable recovery stories. For a time, that is exactly what they were.

These enormous birds had been driven to the brink of extinction, with their population dropping into the 20s by the mid-1980s.

By the end of December 2025, roughly 600 California condors remained alive. About 65% lived in the wild, while the rest were held in captivity. Against that backdrop, the newest figures are difficult to dismiss.

Lead exposure is increasing, as are fatalities. That appears to contradict decades of work designed to safeguard the birds, including restrictions on lead ammunition and public-awareness campaigns explaining the harm lead causes to scavengers such as hunters’ and ranchers’ carrion feeders.

The increase in California condor poisoning

The situation becomes more understandable when considering how condors live across the landscape. New research indicates that rising poisoning rates do not show that the policies have failed.

Instead, the birds and their surroundings have altered in ways that make the issue more difficult to manage.

The study’s senior author, Myra Finkelstein, is an adjunct professor of microbiology and environmental toxicology at UC Santa Cruz.

“We feel this is critically important research that reveals the lead bans and outreach in California have been effective at reducing condor lead poisoning risk,” said Finkelstein.

“Together, our results show that multiple factors have influenced condor blood-lead levels, including changes in wild behavior by condors and shooting behavior by humans.”

How condors come into contact with lead

The California condor is North America’s largest land bird. Adults have a wingspan of approximately 2.9 metres. They are largely black, with bald red-orange heads, and can live for at least 60 years.

They also breed at an exceptionally slow rate, typically producing only one egg every two years. This means each adult bird is important.

Condors do not hunt live prey; they consume carcasses. That feeding behaviour is precisely what exposes them to danger.

When hunters use ammunition containing lead, minute pieces of bullets may remain in animal carcasses or in gut piles left in the field.

Condors, eagles and other scavenging animals eat this material and ingest the lead. Even low doses can harm the nervous system, debilitate birds and prove fatal.

What the long-term record reveals

The research used an unusually valuable wildlife dataset. Every free-flying condor has a wing tag, many are fitted with GPS telemetry tags, and field staff monitored their behaviour almost daily between 1996 and 2023.

This provided scientists with an exceptionally detailed record of where the birds travelled, what they consumed and how their blood-lead concentrations shifted over time.

The findings are bleak. In the central and southern flocks, lead poisoning was the leading cause of condor deaths, accounting for 62% and 44%, respectively.

Over the last five years, the number of birds with potentially fatal lead levels in their blood nearly doubled.

Condors are behaving more like wild birds

Initially, these patterns can make conservation measures appear less effective than anticipated. However, the data point to another change.

Condors are making less use of the safe food supplied by conservation teams at feeding stations. During the 27-year study, use of these lead-free feeding sites fell by 52% among birds in the central flock and by 85% in the southern flock.

They also spent less time close to release sites, where education programmes and enforcement of lead-ammunition bans are likely to be most robust. Their time in these areas declined by 42% and 70%.

“Thanks to the heroic efforts to bring condors back from near-extinction and track their recovery, we have a uniquely complete data set for this species,” noted study lead author Victoria Bakker, a quantitative conservation biologist at Montana State University.

“It was this decades-long record of behavior and health for every individual condor that allowed us to account for the multiple drivers of lead exposure and measure the true effectiveness of outreach and lead-ammunition bans.”

This is significant because condors travelling further afield have a greater chance of encountering contaminated carcasses. Only a small number of harmful meals may be sufficient.

Based on blood-lead-level analyses, the study found that fewer than 10 meals from lead-contaminated carcasses in a year can shift condors from being self-sustaining to dependent on conservation support.

The link with wild pigs

The researchers identify wild pigs as a probable part of the explanation. They lacked the evidence needed to demonstrate a direct connection between lead risk for condors and the shooting of pigs for population management. Nevertheless, the overall pattern is consistent.

Wild pigs have become widespread across California, increasing numbers are being shot, and the study identified greater lead risk associated with pig hunting, alongside a strong relationship between pig hunting and pig control.

This creates an issue even if lead bans are performing better than the headline trends imply. Earlier work by Finkelstein helped establish the connection between lead bullets and condor poisoning, contributing to California’s statewide 2019 ban on lead ammunition for hunting.

A partial ban within condor territory had been introduced 12 years before. The new research maintains that these regulations continue to lower risk, but that fresh pressures are concealing their impact.

“The good news is non-lead ammunition for pig hunting is reasonably available and through effective outreach and free giveaways, we can solve this problem while supporting the heritage of hunting and ranching,” said Kelly Sorenson, a recovery partner at the Ventana Wildlife Society.

Why conserving condors is not becoming easier

The authors describe the circumstances through the “Red Queen dynamic”, a concept for systems requiring continuous effort merely to retain the same position.

“Our findings are a reminder to watch for Red Queen dynamics when evaluating conservation measures in today’s complex settings that can mask effectiveness. Otherwise, successful policies and actions could be abandoned,” said Bakker.

California is still the only US state to prohibit lead bullets for shooting wildlife. This means the California condor story extends beyond a single species.

It demonstrates that conservation successes may be genuine but remain vulnerable, particularly as animal behaviour, hunting practices and land use continue to change.

The complete study appeared in the journal Nature Communications.