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When temperatures start to drop, birds handle the transition in different ways. Some travel to warmer temperatures while others tough it out. Some birds even burrow into the mud to escape the cold, right? Wrong.

For thousands of years, people have believed the myth that birds (swallows specifically) will burrow into the mud and essentially hide away for the winter. Most people nowadays know that no birds hibernate, but the myth still persists in some minds.

So where did this theory come from?

Way back in the 4th century BC, Aristotle was one of the first people to delve into the topic of bird migrations. As a naturalist, he noted that birds traveled to warmer temperatures during wintertime. This was pretty revolutionary at the time because no one had ever written it down (it’s unclear whether it was already a widely held belief).

However, he also noted that other birds, including swallows, went into hibernation. The theory was that birds went into a torpid state and hid in trees and mud. At the time, he said many birds went into hibernation, including kites, doves, and storks, but over the years, the hibernation theory stuck with the swallows like gum.

barn-swallow-1246824-639x958For more than 2,000 years, people just went along with the theory. Here’s what some people believed, according to the Migration of Birds:

“Some early naturalists wrote fantastic accounts of the flocks of swallows allegedly seen congregating in marshes until their accumulated weight bent into the water the reeds on which they clung and thus submerged the birds. It was even recorded that when fishermen in northern waters drew up their nets they sometimes had a mixed ‘catch’ of fish and hibernating swallows.”

All of this anecdotal evidence over the years has worked to keep the myth alive. It wasn’t until the 19th century that scientists started definitively proving the hibernation or burrowed in mud theory wrong.

Interestingly enough, the theory wasn’t all that outrageous. Birds don’t hibernate, but some hummingbird species will enter a temporary state of torpor when it becomes extremely cold. They might be hanging upside or look like they’re dead, but most of their functions just slow significantly.

Also, swallows, which make their nests using mud, are often seen in muddy areas and around rivers. Putting those two things together could conceivably make someone believe that swallows do hibernate.

If you’re interested, check out some of the other bird myths we’ve tackled over the years.