Who’d have thought a twitcher’s photo would reveal so much about bird patterns – and our warming planet? What looked like an odd-coloured jay in a Texas suburb has turned out to be a groundbreaking discovery: a natural hybrid between two species that, until recently, didn’t share the same habitat.
The two different parent species – the green jay and blue jay – are separated by seven million years of evolution, and their ranges didn't overlap until recent decades.
Biologists at the University of Texas at Austin say the bird may be one of the first known animals to result from climate-driven shifts in species ranges.
Brian Stokes, a graduate student in ecology, evolution and behaviour and first author of the study, said:
"We think it's the first observed vertebrate that's hybridized as a result of two species both expanding their ranges due, at least in part, to climate change."
While studying green jays for his PhD, Stokes monitored birdwatching groups on social media, where enthusiasts posted photos of their sightings. It was one of several methods he used to find birds for genetic sampling – capturing them for blood samples then releasing them unharmed.
A photo of a blue bird with a black mask and a white chest, posted in San Antonio caught his attention. It resembled a blue jay, but was different. He visited the house to try and spot it himself and managed to get a blood sample.
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Biology professor Tim Keitt confirmed the theory that the bird is a male hybrid of the green jay mother and a blue jay father. Only one other green and blue jay hybrid is known of, when it was bred in captivity in the 1950s.
Back in the 1950s, the range of green jays hardly ever stretched to reached southern Texas from Central America; the range of blue jays – common across eastern US – didn’t reach further than southeast Texas. The two species rarely, if ever, crossed paths. But as green jays have moved north and blue jays have spread west, their ranges now overlap around San Antonio.
Most known vertebrate hybrids, such as polar bears and grizzly bears, are linked to human activity. This can occur when one invasive species is introduced to an area, or when one species moves into another’s range. But in this case, changing weather patterns seem to have pushed both species of jay into shared territory.
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"Hybridization is probably way more common in the natural world than researchers know about because there's just so much inability to report these things happening. And it's probably possible in a lot of species that we just don't see because they're physically separated from one another and so they don't get the chance to try to mate," said Stokes.
Main image: Brian Stokes/University of Texas at Austin
