Virgin Births: The First California Condor Chicks Born from Unfertilized Eggs

The critically endangered California condor has skirted the line of extinction since 1987– when the last remaining wild individuals were captured as part of a last-ditch conservation effort by the U.S. government.

Considered one of the rarest birds in the world, California condor numbers drastically declined throughout the 20th century due to lead poisoning, poaching, and habitat loss. In the ‘80s, their total population reached an all-time low at just 27 birds left in the world.

The surviving condors were put in captive breeding programs in Southern California and by 1991 California condors were being reintroduced to the wild. The current estimation of California condor populations is about 500 birds, thanks to the success of wildlife breeding programs.

During a routine analysis at the San Diego Zoo Wildlife Alliance breeding program, conservation scientists found two condor chicks that hatched from unfertilized eggs. Samples confirmed each chick shared DNA with its respective mother. But in a shocking twist, neither bird was genetically related to a male, meaning this is the first instance of biologically fatherless chicks in the California condor species.

Both of the chicks are entirely homozygous, instead of having a mix between two parents, 100% of the baby condors’ genes are the same. Notably, the chicks are also both male. Because of California condors’ genetic makeup, females reproducing by themselves can only give birth to male offspring.

“This is truly an amazing discovery,” said Oliver Ryder, the Director of Conservation Genetics at San Diego Zoo Wildlife Alliance. “We were not exactly looking for evidence of parthenogenesis (asexual reproduction), it just hit us in the face."

Parthenogenesis is a naturally occurring form of asexual reproduction where an egg can develop into an embryo without being fertilized by a sperm. This phenomenon is well known in the scientific community, and common in insects, but relatively rare in birds.

“For other species it seems to be sort of a last-ditch effort to save themselves,” said Dr. Samantha Wisely, a conservation scientist with the University of Florida.

Both of the condor mothers were housed with fertile male partners, who they had previously produced offspring with. So this discovery is not only the first time asexual reproduction has been seen in California condors, it’s also the first time parthenogenesis has been confirmed in any bird species where the female had access to a mate.

Published in the Journal of Heredity, this unprecedented discovery could have far-reaching impacts on conservation and genetic science. “These findings now raise questions about whether this might occur undetected in other species,” said Ryder.