The takeaway: Most animals you see have a clear genetic heritage: the mother and father were the same species. But in some cases, different species interbreed, creating a rare and often bizarre hybrid species. Climate change may be making this more common.
A couple of years ago, a resident of San Antonio posted to a birding group on social media a curious picture: a bird with heavy black neck and facial patterning but a blue body.
The dark neck sure looked like a green jay, but the blue body was totally blue jay. So what the heck was this?
The curiously colored bird drew the attention of ornithologists, who visited the site, captured the bird, and took a blood sample in order to perform a genetic investigation. Researchers thought they would find a blue jay with a genetic mutation, but instead found through DNA sequencing that the bird had parents from two different species.
Examples of Hybrid Bird Species
Hybrid birds are rare but not unheard of. The most commonly seen include swans and geese, Brewster’s and Lawrence’s warblers (which are hybrids of blue-winged warblers and golden-winged warblers), and mallard hybrids. There are also hybrid gulls and pheasant and grouse hybrids. Rose-breasted grosbeaks and black-headed grosbeaks are also known to hybridize in areas where their ranges overlap.
Hybrid species are not relegated to the bird world. Likely the most common is the mule, which is a cross between a horse and a donkey, and bred that way on purpose. Other examples include crosses between bear species and a hybrid of a lion and a tiger.
What Causes Hybrid Bird Species
In general, the cause of hybrid bird species is the same as the cause of other hybrid animal species, and even hybrid plant species. Hybrid breeding occurs when two different but closely related species mate, resulting in an offspring that has a genetic mix of both parents.
While humans can create hybrid species on purpose, in nature it occurs when two parent species overlap in so-called “hybrid zones.” Natural hybridization can also occur due to habitat modification through acts such as urbanization and deforestation, both of which may lead birds to seek out new living spaces.
There’s another possible reason, which takes us back to the blue/green jay—dubbed a “grue jay”—in San Antonio: climate change.
Role of Climate Change in Bird Hybridization
As the authors explained in Nature Notes, climate change likely played a significant role in this particular hybridization.
Green jays used to be found along the Texas-Mexico border, but have relatively recently expanded their range 200 miles to the north–a common thread among species in North America who move north in search of cooler weather. (In general, in the middle latitudes, with all other factors being equal, the temperature drops by about 1 to 1.5 degrees F for every 70 miles you head north.)
Blue jays, meanwhile, have expanded their range due to both climate (causing them to move north) and urbanization (causing them to move west in this particular part of Texas).
Seeing Hybrid Bird Species From a Smart Bird Feeder
As stated in the study, animal species hybridization is not rare, but the fact that both the blue jay and green jay experienced range changes is.
“We believe this hybridization event joins a growing list of increasingly unexpected outcomes of contemporaneous range expansions fueled by anthropogenic global change,” the authors wrote. “As birds are keystone species in ecological webs and reservoirs for zoonotic diseases, the creation of unique genomic contexts resulting from climate-driven hybridization is a phenomenon of both scientific and practical importance.”
Meanwhile, the grue jay in San Antonio, reports ABC News, was found to be a male about 4 years old. He’s still alive and continues to be spotted outside of the Alamo City.
With a smart bird feeder like those from FeatherSnap you have a much better chance of spotting these unusual hybrid species. Watch your feed carefully for unusual birds, or birds that the built-in AI identification tool struggles to name. Once your feeder is working, use these tips and tricks to entice even more birds to your yard.