Researchers at The University of Texas at Austin have identified what appears to be a naturally occurring hybrid between a green jay and a blue jay, a pairing they believe may have been made possible by recent climate-driven shifts in habitat ranges. The two parent species are separated by roughly seven million years of evolutionary history and, until just a few decades ago, lived far apart.
“This looks like the first documented vertebrate hybrid formed because both species expanded their ranges—at least partially due to climate change,” explained Brian Stokes, a UT graduate student in ecology, evolution, and behavior, and the study’s lead author.
Hybrid vertebrates have been seen before, Stokes noted, but usually under human influence—such as the spread of invasive species or the overlap of ranges caused by one species expanding into another’s territory. Examples include grizzly–polar bear hybrids. In this case, however, both the green jay and blue jay appear to have expanded their ranges simultaneously due to changing weather patterns.
Back in the 1950s, green jays, which thrive in tropical environments across Central America, barely reached into southern Texas, while blue jays were limited mostly to the eastern U.S., extending only as far west as Houston. The two rarely met. Over the years, though, green jays pushed farther north and blue jays farther west, with their habitats now intersecting around San Antonio.
While monitoring online birdwatching communities for sightings of green jays, Stokes came across a photograph of an unusual bird—blue with a black mask and white breast—taken by a resident just outside San Antonio. Though it resembled a blue jay, it was distinctly different. The homeowner invited him to investigate.
“On the first day, we couldn’t catch it—it was too clever,” Stokes recalled. “But on the second day, we finally got lucky.”
The bird was eventually caught in a fine mesh mist net, a nearly invisible barrier strung between poles that birds often fail to notice mid-flight. Stokes collected a blood sample, placed a band on its leg for future tracking, and released it unharmed. Interestingly, the bird vanished for years before reappearing in the same woman’s yard in June 2025.
“It was almost pure chance,” Stokes said. “If it had shown up in another yard nearby, it probably never would’ve been noticed.”
Genetic testing confirmed the bird was a hybrid, the offspring of a green jay mother and a blue jay father. Its appearance closely matched a hybrid bird created in captivity in the 1970s, which is preserved today in the Fort Worth Museum of Science and History.
“Hybridization likely happens much more often than we realize,” Stokes added. “In many cases, species simply don’t have the opportunity to meet, so we miss seeing these events.”
The study, coauthored with integrative biology professor Tim Keitt, was published in Ecology and Evolution. Their research received funding from the ConTex Collaborative Research Grant, the Texas EcoLab Program, and Planet Texas 2050, a UT grand challenge initiative.
Although Stokes and Keitt chose not to name the hybrid, other naturally occurring cross-species animals have earned popular nicknames—like the “grolar bear” (grizzly–polar bear), “coywolf” (coyote–wolf), and “narluga” (narwhal–beluga).