BOISE, Idaho - Lead poisoning caused half of the California Condor deaths that occurred over the winter in the Arizona-Utah population, a rate consistent with the entire condor population in California, Arizona, and Utah, according to The Peregrine Fund, an Idaho-based conservation organization.
Of the eight condors that died between December 2012 and February 2013:
Four died of lead poisoning;
Two died of trauma possibly caused by a predator; and
Two were unrecoverable.
"It's been a tough season for condors," said Chris Parish, director of The Peregrine Fund's condor reintroduction project. "The good news is that we currently have as many as a half-dozen active nests and 72 birds flying free in the wild in Arizona and southern Utah, a true testament to the species' resilience."
Of the 54 necropsies performed since The Peregrine Fund began releasing condors to the wild in 1996, lead poisoning accounted for 50 percent of deaths, followed by predation at 30 percent, Parish said. This year, The Peregrine Fund's field crew captured nearly all the condors in Arizona and Utah and discovered that 39 percent had toxic levels of lead in their blood. The crews treated the birds with chelation therapy, the same process used to eliminate lead from humans.
"Fortunately, we were able to capture, test, and treat most of the birds," Parish said. "Our biologists had to sit and wait patiently while the majority of the flock returned from the feeding grounds in southern Utah where lead-reduction programs are just getting under way."
Based on more than 10 years of data, the birds are most likely to encounter lead during and after the hunting seasons in northern Arizona and southern Utah, Parish said. The most recent necropsy, conducted on Condor #210, showed acute lead poisoning, with extremely high levels of lead and 10 fragments in her digestive tract. Further analysis showed that her last meal consisted of deer.
Condors encounter lead when eating animals that have been shot with lead bullets, which can fragment into dozens of tiny pieces, some too small to be seen, and disperse widely in the animal's body.
"We expect predators and other natural factors to claim the lives of condors," Parish said. "But anyone who kills an animal, including those dispatching livestock and hunting varmints, can make a significant impact by simply switching to non-lead ammunition like solid copper bullets, which rarely fragment."
Since 2005, hunters on the Kaibab Plateau in northern Arizona have voluntarily assisted efforts to protect condors from lead, with more than 80 percent of hunters participating in the Arizona Game and Fish Department's lead reduction program. That rate has climbed to as much as 90 percent over the past six years. Last year, 88 percent either used non-lead ammunition or removed the remains of shot animals from the field.
In response to the shifting pattern of condors now feeding extensively in southern Utah, the Southwest Condor Workgroup supports efforts by the Utah Division of Wildlife Resources to ramp up education and outreach efforts there. The Utah program resulted in nearly 50 percent voluntary hunter participation in the 2012-13 season - similar to the first year of Arizona's effort in 2005.
"We have come a long way since identifying lead poisoning as the primary cause of death for this reintroduced population," Parish said. "If we are to achieve our goal of a self-sustaining population, we're going to need more help. It has been my experience that when hunters find out what is happening, they are more than willing to join the effort."
The recovery effort is a cooperative program by federal, state, and private partners, including The Peregrine Fund, Arizona Game and Fish Department, U.S. Fish and Wildlife Service, Arizona Strip Field Office of the Bureau of Land Management, Grand Canyon and Zion national parks, Utah Division of Wildlife Resources, and Kaibab and Dixie national forests.