The California condor doesn’t need more bad news. Captive-breeding programs have brought the bird back from the edge of extinction, but habitat loss and lead poisoning have prevented a stable recovery in the wild.

A new study from UC San Diego raises more reason for concern: A wild population of condors along the central coast in Big Sur has been exposed to pesticides and other toxic substances linked to thinning of eggshells.

About 40 percent of breeding-age condors along the coast have been exposed to DDE, a form of the banned pesticide DDT, which is found in the carcasses of marine mammals — like sea lions — that the scavenger birds regularly feed on.

The findings, published Monday in the journal Environmental Science and Technology, also showed that the coastal birds had elevated levels of polychlorinated biphenyl, or PCBs, when compared to their inland counterparts.


“It is disheartening, because I feel like future release plans — I don’t know where they’re going to release” more condors again from the breeding programs, said Carolyn Kurle, co-author of the study and a researcher at UC San Diego. “The coast seemed like a good idea, but now that we showed these high levels of contaminants in birds that forage on the coast, it might not be the best idea.”

× California Condor

Having once fed on the carcasses of woolly mammoths, California condors today typically feed on dead land animals such as deer, goats and sheep.

Because biologists have hypothesized that condors fed on dead marine mammals at the end of the last ice age, many hoped a seafood diet could be a healthy source of sustenance for the scavengers. In fact, condors that spend more time along the coast have had a better chance of surviving than those living inland due to the supposedly greater presence of lead there.


However, the new report estimated that eggs from the shoreline condor population have a 20 percent to 40 percent lower hatching success rate than non-coastal breeders.

“They’re not reproducing in the numbers that would lead to a strong recovery,” Kurle said. “We can infer that the reproductive failure in (coastal) birds in Central California is from DDT.”

The California condor is one the largest birds in North America, with a roughly 10-foot wingspan and weighing up to 25 pounds. Condors once flew up and down the coast from Canada to Baja California and populated states such as Texas, Florida and New York.

By the early 1980s, less than two-dozen condors survived in the wild, according to the U.S. Fish and Wildlife Service. By the end of that decade, the last birds were placed in captive-breeding programs at the San Diego and Los Angeles zoos.


Today, there are more than 420 condors in the world, with breeding programs in California, Arizona, Utah and Mexico, the U.S. Fish and Wildlife Service said. Wild populations live in California, Baja California and Arizona.

More than half of the condor population currently exists in the wild, with about 155 birds living near release programs in Big Sur, Pinnacles National Park and Los Padres National Forest.

But the species is far from establishing self-sustaining populations. Deaths have largely outpaced successful births in the wild, requiring conservationists to regularly release more captive-bred juveniles.

“California condors in the wild are still struggling,” said Steve Kirkland, California condor field coordinator the U.S. Fish and Wildlife Service. “We are still losing more birds to human-related causes of mortality than are produced in the wild, with lead poisoning the primary impediment to recovery.” Other causes include hunting, electrocution by power lines, destruction of habitat and poisoning from bait meant for other animals.


In response to concerns about condor mortality, lawmakers outlawed hunting big game with lead bullets in designated ranges in 2008.

The California Rifle and Pistol Association and other groups have disputed that bullets are poisoning the vultures, pointing to continued rates of lead poisoning despite the restrictions.

“They’ve always been saying that, and we think they’re wrong that lead is coming from lead ammunition,” Chuck Michel, president of the California Rifle & Pistol Association.

The current ban has “not had any notable impact,” Kirkland said. “This is likely due to the fact that condors feed on animals shot with lead ammunition that are not covered under that (state law).”


As the result of further legislation, a ban on all hunting with lead ammunition is being phased in statewide during the next three years.

In the meantime, those dedicated to protecting the condors have been going to great lengths to maintain populations. In some cases, scientists have replaced compromised eggs in the wild with those bred in captivity. The birds lay an average of an egg every two years.

“When we saw this eggshell thinning, we were able to compensate for that,” said Michael Mace, curator of birds at the San Diego Zoo Safari Park. “We would take that thin-shelled egg and give a normally shelled egg to those condors in the wild. But that’s a short term mitigation.”

Between 2010 and 2014, the condor population increased from 370 to 421. Last year, the U.S. Department of Fish and Wildlife recorded more wild-fledged nests than deaths, but officials cautioned that it’s still too early to confirm a trend.