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North America was once home to tens of thousands of condors

tens of thousands of condors
California Condor. Photo courtesy of San Diego Zoo Wildlife Alliance

Despite declining to only 22 birds in the 1980s, the California Condor genome shows a surprising amount of genetic diversity, according to a study published May 13 in the journal Current Biology.

The study is the first to begin quantifying diversity across the entire condor genome, which offers researchers needed baseline information to inform future research and conservation of the iconic species, the largest species of land bird in North America. The researchers say that the quality of their genome assembly is among the highest for any bird genome sequenced to date.

In comparing the complete genomes of two California Condors with those of an Andean Condor and a Turkey Vulture, UC San Francisco and UC Berkeley scientists did find genetic evidence of inbreeding over the past few centuries, but, overall, a wealth of diversity across most of the genome.

“You need genetic diversity in order to adapt, and the more genetic diversity they (California Condors) have, hopefully, the more chance they have to adapt and persist,” said Jacqueline Robinson, a UCSF postdoctoral fellow and first author of the paper about the analysis. “Our study is the first to begin quantifying diversity across the entire California Condor genome, which provides us a lot of baseline information and will inform future research and conservation.”

The health of the bird’s genome is probably due to the species’ great abundance in the past. Robinson and her colleagues, including Rauri Bowie, UC Berkeley professor of integrative biology, used statistical techniques to estimate the bird’s historical population and found that it was far more abundant across the United States a million years ago than even the Turkey Vulture, America’s most common vulture today. The bird likely numbered in the tens of thousands, soaring and scavenging from New York and Florida to California and into Mexico.

“We estimated that prior to 10,000 years ago, there were tens of thousands of condors,” says Jacqueline Robinson of the University of California, San Francisco. “The relatively high level of diversity in condors today is a legacy of their high historical population sizes.”

For context, the world population of California Condor at the end of 2020 was 504 birds. Of these, 329 were wild and free-flying while 175 were captive and living at five different breeding centers.

“Our results accord with what we know from the fossil record, which is that the ancestors of California Condors once ranged across the contiguous United States,” Robinson adds. “Over time, the condor’s range shrank until they only persisted along the Pacific coast, where they were able to incorporate the carcasses of large marine mammals into their diet.”

The species experienced a long-term decline over geologic time that “predates its recent near-extinction driven by human activity,” Robinson says. “This isn’t to say that the California Condor was already doomed to extinction because we found historical declines in the Andean Condor and Turkey Vulture as well, and Turkey Vultures are extremely abundant today. The consistent pattern of historical decline in these species may be connected with the decline and extinction of avian scavenger species in the Americas since the Pleistocene, but we need to do more research to really address this question.”

A version of this article will be published in “Birding Briefs” in the July/August issue of BirdWatching.

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