California’s endangered condors have a surprising new foe
Researchers couldn’t figure out why the birds were dying — then they turned up an unusual suspect.
When it comes to conserving the California condor, progress is precarious. One wild pair recently laid the first egg in northern California for the first time in a century, and there are now more than 400 condors in the wild, up from 26 in 1987. It sounds like the start of a comeback story.
But as a new study in Nature Communications highlights, condors are still threatened by a stubborn, surprising enemy: lead poisoning. The birds are not ingesting lead directly, but they feed on animals that were shot by hunters and left on the landscape.“One little fleck of lead gets in, and this great, tough, resilient animal just crumples,” says study co-author Joe Burnett, a biologist for the nonprofit Ventana Wildlife Society and a National Geographic Explorer who’s been working with condors for more than 30 years.
When ingested, lead absorbs into the birds’ blood. It can disrupt their eating, make them anemic, and cause their kidneys and heart to fail. If enough lead accumulates, these symptoms can be severe and eventually fatal. Condor #168, a 29-year-old Californian condor known as Beak Boy, is a poster child for the effects of this toxic metal. Condors are supposed to mate for life, but he’s had two mates. Both died of lead poisoning.
“They’re very social animals. They’re supposed to have these lifelong bonds,” says Burnett. He notes that lead poisoning affects the flock in multiple ways. “The clearest one is mortality. But it also impacts the social fabric that can keep a flock so strong.”
To end this cycle of lead poisoning in condors and other wildlife, California began a phase-out of lead ammunition in 2013, and a statewide ban went into effect in 2019. It’s the only such ban in the country. (Legislation to limit the federal government’s ability to ban lead ammunition on some federal land is currently being considered in the U.S. Senate.)
But even after the lead ban, biologists kept finding condors dead in the field, and necropsies revealed lead poisoning, says Victoria Bakker, an ecologist at Montana State University who led the new study. “It was so discouraging,” Bakker says. “How could that be when we have lead bans?” The answer, as Bakker and Burnett’s new paper suggests, is simple. Bans are only effective when they’re followed.
A treasure trove of condor data
The study focused on two flocks, one each in central and southern California. Nearly every wild condor is equipped with a radio telemetry tracker, so Bakker could reconstruct individuals’ travel histories, including where they stopped to feed. Over the study period of 1996 to 2023, the condors were acting “wilder”: flying farther from release sites and visiting human-supplied feeding sites less frequently. “Ultimately, it’s the behavior you want,” Bakker says. “It’s a success of recovery. But we have to get lead off the landscape.”
When condors in the study died, researchers recorded their lead levels and fed that data into a computer model, along with other variables such as hunting and amplified conservation efforts like campaigns against lead bullets. The results told them whichfactors most strongly correlated with a condor’s lead exposure and their likelihood of dying from lead poisoning before and after the lead ban in 2019.
At first glance, their findings seemed grim. Condors were increasingly exposed to and dying from lead, even after the ban, when the percent of sampled condors who had some degree of lead poisoning rose to 42 percent (it had been 28 percent before the ban).
And the population was still not growing quickly enough to be sustainable without captive-bred birds being released into the wild. For the southern flock, wilder behavior—flying farther from release sites and eating fewer human-offered meals—explained the disappointing results. They were more likely to encounter contaminated food, even with the lead ban. But for the central flock, the behavior model didn’t fully explain condor deaths. The researchers were missing a piece of the puzzle. “We were pulling our hair out,” Bakker says.
Then the subject of wild pigs came up.
Invasive wild pigs are on the rise in California, and so is wild pig hunting, especially in the central flock’s range. But because they’re a generally considered to be a nuisance species rather than big game, which typically has stricter regulations, people hunting them might not be aware that they can’t use lead shot to do so, says Chris West, a senior wildlife biologist with the Yurok Tribe who was not involved with the study.
“Some of these people may be in violation of the law, but not because they don’t want to follow the law. It’s because they don’t know,” West says. Big game hunters generally pay attention to year-to-year regulation changes, but land managers or ranchers who use firearms to control pest wildlife populations might not check as often, he says.
So Bakker added the numbers of pig hunting tags claimed each year to the model. Suddenly, the numbers made sense.
“Lo and behold, that was such a clear predictor of the increased lead exposure for the central flock,” Bakker says. When more pig hunting happened, more condors died from lead poisoning. For the researchers, that suggests lead is still being used to control wild pig populations, despite the ban. But future research should keep exploring this potential relationship, including better data collection on wild pig populations and hunting and using environmental DNA swabs to home in on condors’ diets, Bakker says.
A change for good
More outreach with these groups could increase awareness of the environmental effects of lead shot, ultimately helping condors, Burnett says. And just getting the word out about using lead-free ammunition even for pest species control can make a big difference for condors, the study found.
When groups had done more education and lead-free ammunition distribution, condors had lower rates of lead exposure and lead-related mortality. And a statistical analysis showed that lead bans make a difference: Fewer condors died of lead poisoning than would have without the lead ban. Essentially, the lead ban worked well enough to counteract the effects of the condors behaving more wildly and pig hunting, Bakker said. But there’s still room for improvement.
To the authors, that suggests a need for more outreach about the importance of lead-free ammunition as the condors expand their ranges and rely less on human-supplied food. “The birds are wilding at a faster rate than we can do the outreach,” Burnett says. “Clearly, we have to increase our outreach, because the birds aren’t stopping.”
In the meantime, Beak Boy is rearing his chick as a solo dad. The scientists hope the chick will grow up in a world with less lead in it. “I don’t like to say condor conservation is easy, but in one way, it is,” West says. “It’s a single risk factor. If we can move the needle on lead, we can move the needle on condor recovery.”
