Updated October 24, 2025 at 3:55 PM EDT
What happens in the wild when sparks fly between a blue jay and a green jay?
Until recently, no one had any idea.
But then, in 2023, someone spotted a rare kind of visitor to a backyard outside of San Antonio, Texas.
And it was — you guessed it — a rare new hybrid that researchers have dubbed the “grue jay.”
It could be the first natural hybrid between the two species.
“We had been asked to come check it out in this person’s backyard, and it looked pretty similar to a blue jay, where a lot of the body was kind of this darker blue color that people in a lot of North America are going to be familiar with,” said study author Brian Stokes, a graduate student in ecology, evolution and behavior at the University of Texas at Austin. “But it had some really interesting facial markings that were kind of a deep black color that almost perfectly matched the facial markings of green jay, another jay species we find in south Texas. And so it was an interesting combination of these traits that kind of tipped us off that this bird might be different than just a normal blue jay.”
5 questions with Brian Stokes
How do you know that this is an actual hybrid instead of just a blue jay with a genetic mutation?
“Yeah, that’s a great question, because we were wondering the same thing at first, if it could just be, you know, an odd pigmentation or something like that. We captured the bird in the field and sent off a blood sample that we took for DNA sequencing. And so, we were able to compare actual DNA sequences from its chromosomes and from its mitochondrial DNA to pre-sampled blue jay and green jay DNA and mitochondrial samples to figure out what the purity of this individual bird was.”
So how big of a deal is this kind of a discovery?
“Well, hybridization in birds is actually quite common. It’s thought that between 10 to 15% of all bird species hybridized in the wild.
“But this is a pretty diverged hybrid. So the parent species, the blue and the green jay, are about 7.5 million years diverged, which is fairly long within the span of time that most birds are able to hybridized or willing to hybridize.
“The thing we thought was really interesting is that historically these species were not geographically overlapping with one another. So recent land use change and climate change in Texas has actually allowed these species to now expand their ranges and overlap with each other. And that’s especially true for the green jay, who’s really expanded their ranges over about the past 50 to 60 years.”
Oh, so you’re saying this is a climate change story?
“I think that’s a big part of it. We wouldn’t rule out the role of land use change or urbanization in Texas. There’s a lot of things like water and food … that birds like green jays and blue jays really like. But temperatures in Texas during winter are really increasing, and we’re having less intense freezes compared to about 50 to 60 years ago. And so we’ve seen green jays move northward seemingly in response to those climate changes.”
So, you know, this has happened in other species, too. I’m thinking about the grizzly bear and the polar bear. How common is climate driving these sorts of changes across the animal kingdom?
“This has likely happened throughout biology many, many times, but this is just one of the newest examples of what we would consider anthropogenic-driven hybridization, where these species have just responded to changes in their environment that are driven by human-caused change and been able to now have the ability to mate. And, you know, there’s a lot of behavioral aspects to these species. They’re both social, very intelligent animals. And so, it was pretty surprising they’d be willing to mate with one another.”
So, what’s the fate of this group? Is there a chance that it might have any offspring of its own?
“We think it’s possible, although we haven’t seen any evidence that it’s attempted to yet.
“It likely has the exact same chromosome number as both the maternal and paternal species, which is important for producing future hybrid generations. So, an example like the mule, a hybrid between a horse and a donkey, those parent species have a different chromosome number. So that’s part of the reason why mules are not able to produce offspring readily.
“So, it’s theoretically possible, but there’s a lot of behavioral barriers for birds and other species that are socially complex, where there’s a lot of choice going into who you’re deciding to mate with as a bird. And so, it’s likely that a green jay is going to prefer to mate with a green jay. A blue jay is going to prefer to mate with a blue jay. But obviously that’s not always the case. As we’ve seen this hybrid occurred where species were willing to mate with someone that didn’t look exactly like them. So, you know, it’s theoretically possible, but we haven’t seen the evidence of that yet.
This interview was edited for clarity.
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Kalyani Saxena produced and edited this interview for broadcast with Micaela Rodriguez. Michael Scotto adapted it for the web.
This article was originally published on WBUR.org.
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