California condors are close to being able to form a self-sustaining wild population (Image: David McNew/Getty)

With wingspans of up to 3 metres, it should be hard to miss the largest bird in North America – but there aren’t a lot of them. The California condor is only just hanging on in its home state, but thanks to a gargantuan conservation effort, the tide may finally be turning.

To save the species, the last few California condors were taken from the wild in the late 1980s, after lead poisoning from gun ammunition nearly drove the birds to extinction, with only around 22 birds left in the wild. Since 1992, there have been multiple reintroductions to the wild, and there are now more than 150 individuals flying over California and nearby areas in Arizona, Utah and Baja in Mexico, but their survival is still dependent on help from humans.


To establish themselves in the wild, condors have to survive long enough to reproduce. Now, thanks to regular monitoring, training and medical treatment, they are finally on the brink of forming a self-sustaining population.

Shock therapy

Electric cables are one problem for the condors. Flying at heights of up to 4.6 kilometres, while focusing on the ground below, it can be hard for these huge birds to notice utility lines when landing.

“As they go in to land at a carcass or to roost for the night, they just don’t see the power lines,” says Bruce Rideout of San Diego Zoo. “They have a very large wingspan, which can bridge the gap between power lines, resulting in electrocution if they touch two lines at once.”

Power-pole aversion training has helped condors avoid electrocution in the wild (Image: US Fish and Wildlife Service)

But there is a solution. The condors are caught several times a year for monitoring and health screening, when they also receive cable aversion training. Artificial utility poles, placed in large aviaries or training pens, teach these birds to stay well clear of cables by giving them a painful electric shock.

Before this training was introduced, 66 per cent of released birds died of electrocution, but this has since dropped to just 18 per cent, according to work by Rideout and his colleagues, published in Biological Conservation. “Utility lines are not a significant problem anymore,” says Rideout.

Purging the poison

Lead poisoning is still a big threat, though. “Condors have a very slow but efficient digestive system,” says Allan Mee of the Golden Eagle Trust.

When they eat carcasses that have lead ammunition in them, for example when hunters take away the edible parts of a deer but leave its guts behind, they absorb large quantities of lead. This affects the birds’ nervous systems, fertility and can lead to kidney failure and death.

A partial ban of the use of lead ammunition throughout the condor’s range in 2008 seems to have had little effect. Condors are usually re-captured about twice a year for blood testing and a study by Myra Finkelstein from University of California, Santa Cruz, and her colleagues, published in 2012 found that about a fifth of wild birds had blood levels that required clinical intervention to prevent sickness and death (PNAS, DOI: 10.1073/pnas.1203141109).

Condors with high levels of lead are sent to Los Angeles Zoo where they are injected with calcium EDTA, a chemical that purges lead from the bloodstream over several days.

“If the bird is found via radiograph to have ingested a possible lead item, they will undergo treatment to induce regurgitation of the item, and if necessary, surgery,” says Finkelstein. The birds that survive are re-released.

Almost there

The hard work is starting to pay off. In 2000, the annual mortality rate for adult condors was 38 per cent, but over 2001 to 2011, this dropped to an average 5.4 per cent per year.

Ensuring that each individual lives for as long as possible is crucial if the population is ever going to sustain itself, without the need for further reintroductions. Condors take 5 to 6 years to reach maturity, and usually don’t successfully raise young until they have themselves been flying in the wild for seven years.

Rideout and his colleagues estimate that condors’ average survival time in the wild was just under 8 years, leaving it very close. They calculate that if adult annual mortality rates could drop from 5.4 per cent to 5.3 per cent, this might be enough for populations to become stable.

In the meantime, training, testing and treating the condors is an important stopgap. “Although these measures are not sustainable indefinitely, they are essential for now,” he says. “They are truly magnificent birds that are worth every effort we put into recovering them.”

Journal reference: Biological Conservation, DOI: 10.1016/j.biocon.2015.07.012