Meet Grue Jay: Rare hybrid offspring of a blue jay and a green jay born of climate change

A woman in a San Antonio suburb took a photo one spring morning in 2021 of a bird in her yard that looked odd. Its feathers were as blue as any Blue Jay, but its body patterns and chunky black mask appeared borrowed from another bird. Not understanding what she was looking at, she posted pictures and released them on the internet.

Her sighting was noticed by Brian Stokes, a University of Texas at Austin graduate student studying Green Jays. He had the intuition that this odd bird was not a color morph but something much more bizarre. This was a story of chance, perseverance, and scientific discovery one that illuminated the path that changing climates are recasting on the natural world.

When Stokes entered the suburban neighborhood, he carried mist nets with him—delicate mesh that can snare birds without injuring them. The rare jay did not readily surrender, escaping on the first try. On the second try, it flew directly into the net.

In his possession, the bird displayed a mix of traits. Its feathers leaned towards Blue Jay, but the mask, bib, and some of the feathers echoed Green Jay. Stokes quickly took a minute blood sample, banded its leg, and released it into the neighborhood. Waiting then began.

To his surprise, the bird vanished for a couple of years before appearing once more in the same backyard in June 2025. Why it liked that spot is not clear, but the fact that it returned proved that it could survive for years on its own.

Morphological indicators were intriguing, but genetic testing put it in the bag as Stokes had wished. The bird's blood was tested and found to contain mitochondrial DNA of a Green Jay to confirm its mother, and an equal division of nuclear DNA with Blue Jay genes to confirm its father.

This was no vague hybrid but a clear F1 offspring—the direct child of a Green Jay mother and a Blue Jay father. Scientists had previously seen only one such hybrid, reared in captivity in the 1970s and now exhibited in a Fort Worth museum.

This may be the first documented vertebrate hybrid to exist because two species had their ranges overlap as, at least partially, a result of climate change," Stokes explained.

Only a few decades ago, such an encounter would have been impossible. In the 1950s, Green Jays barely reached into Texas from Mexico, and Blue Jays rarely made it farther west than Houston. They lived in separate worlds with little chance of ever meeting.

But with warming temperatures, Green Jays expanded north and Blue Jays shifted westward. Near San Antonio, their ranges overlapped finally. It was the unlikely overlap that had created the rare chance encounter that resulted in the hybrid seen in a back yard.

Professor Tim Keitt, co-author with Stokes of the published study and advisor to Stokes at the University of Texas at Austin, explained that climate-driven range shifts are breaking down long-standing barriers. "It's the reshuffling of species," he said, commenting that these encounters would become more regular in the future.

To put this event into perspective, the research group simulated climate conditions for 1991-2020 and bird sightings for 2000-2023. What the models indicated was that if greenhouse gas levels persist at moderate rates, ranges for which Blue Jays and Green Jays coexist will increase dramatically by mid-century.

Which is to say, this San Antonio bird will not be lonely for long. Other hybrids may already exist, undetected in backyards or woodlands.

Hybridization is natural evolution, but it usually occurs between closely related birds. The Green Jay and Blue Jay diverged some 7 million years ago and are assigned to different genera—Cyanocorax and Cyanocitta. Hybrids between such deep evolutionary lineages are extremely rare.

Hybrids may struggle to survive, living shorter lifespans or being infertile. However, this bird's survival for a few years attests to it not only being viable but being able to adapt. Whether or not it could produce offspring is something yet to be resolved. If fertile, it would be able to pass on its hybrid characteristics to offspring generations, forming a genetic bridge between animals long considered to be wholly distinct species.

Stokes thinks there may be more examples to be found. "Hybridization is probably much more common in the world than scientists know because there's just so much inability to report these things happening," he said.

To scientists, the San Antonio hybrid is something more than a curiosity. It's a reminder that the limits of nature are changing in real time. As climate change continues to reshape habitats, species will meet one another in ways they have not in millions of years. Some will result in competition. Others will yield hybrids that test our theories about evolution.

To the woman who initially saw the bird in her garden, it was a novelty. To science, it is proof that despite millions of years of isolation, nature is still capable of surprise—and that climate change, brought about by humans, is accelerating those surprises.

This jay hybrid gives a strange window into how climatic change has the power to directly reshape ecosystems. As warming changes species ranges, unexpected interactions will become more common, giving rise to new hybrids and derailing evolutionary paths.

From a conservation perspective, researchers will need to consider not just species extinction, but also the creation of new genetic unions.

Studies on these hybrids may give insights into how animals adapt to fast environmental change and help predict future impacts on biodiversity.

Research findings are available online in the journal Ecology and Evolution.

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