Yes, you read that correctly: swoose. And just as you may have guessed, it’s a cross between a swan and a goose. While surprising pairings like this are quite rare, there are other birds that often tip-toe across species boundary lines during mating, resulting in hybrid offspring.
What’s a Hybrid Bird?
In a nutshell, a hybrid bird is the offspring of two distinct bird species. Natural species barriers—song, color, markings, behavior, etc.—tend to keep most birds mingling with their own kind. However, every now and then a hybrid bird will pop up, proving that genetics aren’t always a strict barrier to mating possibilities. The viability—or capacity to survive, thrive, and reproduce—of hybrid birds tends to vary greatly, and many hybrid birds end up being sterile. A swoose hatchling, for example, will rarely live past the fledging stage, whereas many warbler hybrids are able to thrive to adulthood and even reproduce.
Why Do Birds Mate Outside of Their Species?
You may be wondering why a bird would mate with another species in the first place, especially since the health of the resulting offspring can be so precarious. Cross-species mating happens for many reasons, including by accident! While birds use voice and physical features for identification, it’s not impossible that certain birds are mistaken for another species—especially when the two parent species fall within the same genus, or umbrella branch of the evolutionary tree (sparrow to sparrow, hummingbird to hummingbird, etc.).
But hybrids aren’t always an ‘oops’ offspring. Birds of similar species are known to get together when they are faced with limited mating options, too. This could be a result of low population due to environmental challenges or simply living at the edge of their species’ normal range. For example, the northern parula and the yellow-throated warbler live throughout the southern United States. Yet, they tend to be more prone to breeding with each other in the upper Midwest, a region where the population size (and thus number of potential mates) is much lower for both species.
See also: How Do Birds Mate?
Common Hybrid Birds in North America
The swoose has taught us that hybrids can pop up in the most unexpected combinations. There are some bird species that are much more familiar with the art of hybridization. Here are few of the most common hybrid birds in North America:
These guys are one of the most frequent cross-species breeders among birds in North America. Keep your eyes peeled. You’re likely to see all sorts of stunning color combinations and markings. These are the result of interbreeding between different species of hummingbirds.
Steadily underrated when it comes to ooh-ing and ahh-ing over birds, ducks actually have a plethora of appeal for showcasing the possibilities of species diversification. Ducks offer an abundance of rich tapestries made up of colorful combinations of tail feathers, striped wings, and more. They are known for frequently producing hybrids.
If you really want to challenge your bird identification skills, try and sort out all the distinct species contained within the gull family. Western gull and glaucous-winged gull hybrids are common in the Pacific Northwest. The glaucous-winged gull regularly hooks up with the herring gull in Alaska. Even expert birders can break into argument distinguishing between pure gull species and all their hybrids!
WarblersGolden-winged warblers and blue-winged warblers often get together to create one of two possible hybrids: a Brewster’s warbler or a Lawrence’s warbler. Scientists categorize the resulting hybrid according to its genetic makeup and features. These two warbler hybrids are super common in the eastern U.S. In 2018, scientists made an exciting discovery: a Brewster’s warbler had seemingly mated with a chestnut-sided warbler, successfully producing another new hybrid. It was essentially a hybrid between one hybrid and one established warbler species. This phenomenon shows the incredible potential for hybrid species to intermingle outside of expectations.
See also: Warblers to Watch for in Winter
How to Identify a Hybrid Bird
Does the idea of hybrid birds have you hyped to identify a few in your own backyard? Here are a few tips. Hybrid birds are most commonly identified by their physical markings. First, take note of color and pattern positioning on the body. Also, listen to the bird’s song, which can provide a helpful clue. While some hybrid birds only express the song of one parent, other hybrids may actually mix and match songs of both parents. Such is the case with the dark-eyed junco and white-throated sparrow hybrid. Finally, be familiar with the types of birds that are common in your region. Knowing who’s around can help you put the visual and aural clues together to crack the case and identify your new hybrid friend. Good luck!