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Parthenogenesis in California Condors Stuns Scientists

By Hugh Powell
portrait-style photo of a California Condor
California Condor by Patrick Sysiong/Macaulay Library.

From the Winter 2022 issue of Living Bird magazine. Subscribe now.

In a surprise finding, researchers reported in October that two female California Condors had reproduced asexually. Hailed in news reports as “virgin births” (the technical term is “parthenogenesis”), the discovery was made possible only because of meticulous records kept during intensive recovery efforts for this federally endangered species. The report appeared in the Journal of Heredity.

Parthenogenesis—or animal reproduction via eggs that aren’t fertilized by sperm—is common in some insects and other invertebrates, but much rarer in vertebrates. A few fish, amphibian, and reptile species produce young parthenogenetically, but in birds it is known only from a domestic breed of turkey and in a few cases with captive lovebirds.

Researchers from a team led by the San Diego Zoo Wildlife Alliance stumbled across the finding while analyzing genetic data for more than 900 California Condors—virtually every young condor that has hatched since a captive breeding program was launched in the late 1980s to save the species from extinction. During their analysis, the researchers were puzzled to find that two condors, both male, showed multiple DNA mismatches with their putative fathers. Instead, they carried two identical copies of their mothers’ DNA at all 21 genetic locations the researchers examined.

Fascinating as the discovery is, it seems unlikely that parthenogenesis will play a role in building up the endangered California Condor’s population numbers. Both young condors lived relatively short lives of about 2 and 8 years, compared to a typical condor lifespan of more than 40 years. Neither bird produced any offspring.

Parthenogenesis is virtually unknown in wild birds, but that could be because it’s so hard to detect out in the field, says Irby Lovette, director of the Center for Biodiversity Studies at the Cornell Lab of Ornithology.

Scientists don’t have deep DNA databases of most wild bird populations for the kind of genetic analysis that yielded this find. Condors were perfectly positioned for such a discovery, Lovette says, because scientists had an exhaustive record of condor parentage for comparisons and complete DNA samples to clinch the result. And the global population of California Condors had already survived a severe population crash (hitting a low of just 22 condors in the 1980s), so the kinds of genetic defects that normally make inbreeding a problem might already have been purged from the population by the time the two parthenogenetic males hatched.

The finding reshapes biologists’ view of parthenogenesis, says Lovette, even if it remains a hard-to-detect curiosity in wild birds. “When you have these anomalous biological phenomena, sometimes they can be used to study parts of the birds’ biology that you wouldn’t be able to see otherwise,” he says. “As scientists we love these little natural experiments.”

The Cornell Lab

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American Kestrel by Blair Dudeck / Macaulay Library

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