Genetic Study Reveals Rich History of California Condors

The California condor is a resilient bird and a new study says their genetic data tells a complex story replete with near-extinction.

A California condor. (Credit: San Diego Zoo Wildlife Alliance)

(CN) — Almost 40 years ago the California condor nearly blinked out of existence. The largest North American land bird sports a wingspan over 9 feet long and feasted upon the carcasses of megafauna 10,000 years ago.

By 1982, just 23 condors were left in the wild and it would take years for it to become clear that feasting on animal carcasses riddled with lead-based ammunition were to blame for the bird’s decline.

These New World vultures once thrived in the tens of thousands across the United States according to a study published Thursday in the scientific journal Current Biology. But with such a dire situation less than 40 years ago, the species risked taking a hit to its genetic diversity due to inbreeding.

Instead, the California condor’s genetic data reveals high diversity, meaning a greater variation when compared to other large birds, like the turkey vulture or the Andean condor, according to the study.

“We didn’t know to what extent California condor genomes would show signs of inbreeding,” Jacqueline Robinson of the University of California, San Francisco and lead researcher said in a statement. “We now know that there was some inbreeding in the wild prior to the start of captive breeding efforts. Future sequencing of more individuals will tell us if there are regions of the genome that have completely lost variability, or if captive breeding and building up the population size over the past few decades has mitigated the effects of previous inbreeding.”

The California condor enjoys a high genetic diversity due in part to there being so many at one point in the U.S. The study marks the first time researchers generated a complete genome sequence for the critically endangered California condor and this will help conservationists with future research.

“Specifically, we can use this genome assembly as a scaffold when analyzing genomes from more individuals in the future, to monitor things like inbreeding, migration of individuals between different wild populations, and levels of potentially adaptive or harmful genetic variants,” Robinson said in an email.

Just two California condors were analyzed as part of this study and future research would like expand that to look at a wider population, Robinson said.

“One of the challenges of the California condor captive breeding program is managing the effects of inbreeding depression, such as a lethal form of chondrodystrophy. Identifying the gene underlying this genetic disorder is one of the goals for future research,” Robinson said.

“The breeding program is a real success story,” said senior conservation advocate Jeff Miller with the Center for Biological Diversity, who was not part of the research. “The effort to save the California condor is an example of how extensive the process was. By happy accident, the condors did really well while in captivity.”

In the early 1980s, U.S. Fish and Wildlife undertook what was then viewed as a controversial move to save the California condor: they would capture all remaining birds in the wild and give them every chance to survive in captivity.

On Easter Sunday 1987, conservationists captured the last wild condor. Animal keeper Mike Clark from the Los Angeles Zoo remembers the day well. Protesters stationed outside the zoo in a large crowd and some people even chained themselves to the fence. Critics of the breeding program thought birds should remain free, even though they were dying at an alarming rate in the wild.

The last wild California condor eventually made its way to the L.A. Zoo.

“AC-9,” Clark said when reached by phone. “It was one of the first birds I took care of here. We took care of him for 20 years.”

He dryly added, “And then he died from lead poisoning.”

Experts can’t say for sure what that bird died from because its body was never recovered. But each condor released back into the wild is tagged and the data shows that this bird stopped moving. Later, experts found that the bird’s mate died from lead poisoning.

Clark calls California condors “behaviorally elastic birds” that can live up to 60 years and thrive in various habitats, from extremely dry cliffsides to damp rainforest biomes.

“They make lemonade out of lemons. When they’re in captivity, they make the best out of their situation. There’s food, shelter, water, there’s no competition for food and there’s a mate,” Clark said. “They just go for it.”

Recovery plans seek to repopulate the Golden State with the California condor like in the Yurok Ancestral Territory and the Redwoods National Park. This is due in part to the breeding program undertaken 40 years ago.

Today there are a little over 300 birds in the wild. There should be hundreds more, but lead poisoning is a persistent threat. In 2019, California banned the sale of lead ammunition, but carcasses flecked with lead shot are still left out in the wild where California condors feed. The L.A. Zoo regularly treats birds for lead poisoning and while some birds survive, they continuously run into the problem of eating food tainted with lead.

“They can’t eat poison every day and live,” Clark said.

A 2012 study from University of California, Santa Cruz found that lead ammunition was to blame for the dramatic drop in the California condor population. The study concluded that the species could never be conservation-program independent if spent lead continued to pop up in the environment.

“The lead is only the thing we haven’t figured out yet,” Clark said. “Well, we have figured it out, we just can’t fix it.”

%d bloggers like this: