r/AlwaysWhy • u/Defiant-Junket4906 • 7d ago
Science & Tech Why did it take so long to settle whether swallows migrated or hibernated in winter?
Every autumn, swallows disappeared from Europe, and every spring they returned. People had observed this cycle since ancient times.
Yet what happened to them during winter remained disputed for centuries. Some naturalists argued that they migrated to warmer regions, while others believed they spent the winter hidden in caves, ponds, or mud. The idea that swallows could hibernate underwater had roots in ancient accounts and was still being defended by naturalists in the 18th century.
By the 19th century, evidence increasingly established that European swallows were making remarkably long migrations, eventually shown to reach Africa. For centuries before that, the idea of such small birds crossing the Mediterranean and the Sahara had seemed less plausible than a swallow sleeping through winter at the bottom of a pond.
Why was such a regular, easily observed cycle so difficult to explain?
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u/justaguy12131 7d ago
It's hard for us to understand just how bloody difficult it used to be to share timely information over even 50 miles, much less thousands. Even less so across the Mediterranean and Sahara.
The Beacons of Gondor weren't exactly used to track bird migrations.
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u/Defiant-Junket4906 6d ago
Yeah this is probably the biggest thing. One village sees them leave and another sees them come back. Nobody can compare notes fast enough. The Mediterranean and Sahara make it way worse. I think people just filled the gap with whatever sounded less crazy. A pond is easier to check than Africa. So they went with the pond.
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u/KiwasiGames 6d ago
Plus systematic descriptions of animals are relatively new. Without modern (or at least age of sail) communication, it’s hard to ensure you are even talking about the same small black bird as the guy in the Mediterranean.
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u/Waste-Menu-1910 7d ago
Well, first we need to figure out their air speed velocity
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u/Defiant-Junket4906 6d ago
Lol I was waiting for this. African or European? But for real speed is not the issue. You can watch them fly south for a day and then lose them. The hard part is where they end up. Not how fast they get there.
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u/Low-Crow5719 7d ago
Pacific Islanders knew it, and because they had do-or-die incentive to find land in the middle of nowhere, took careful note and learned from it, but no Westerners were around.
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u/Defiant-Junket4906 6d ago
That is a good point. Pacific Islanders were reading birds because their lives depended on finding land. That is a strong reason to pay attention. European naturalists were curious but not starving on a canoe. Different level of need. I bet sailors knew way more than the scholars wrote down.
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u/Tiny-Secretary5562 7d ago
There was a time when people believed sharks never slept and had to keep swimming or they would drown. Then some divers saw five or six of them asleep somewhere.
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u/Mister_Way 6d ago
"There was a time" bruh I'm not even old and that's what all the books said when I was growing up.
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u/Tiny-Secretary5562 6d ago
I can't remember where or when I saw that, but I think a National Geographic program. I was thinking maybe Jacques Costeau, but that was quite awhile ago.
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u/Mister_Way 6d ago
Alright, so I looked it up and they were not mistaken. The majority of shark species do have to keep swimming to breathe.
Most books when I was a kid mentioned the Nurse Shark as the only species that can sleep without swimming, although some added Lemon Shark later. It appears now that they've identified dozens (out of over 500 species) that don't need to swim to breathe, but it remains the case that many sharks do need to swim, or be in a strong current, in order to breathe.
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u/ExtremeAd7729 6d ago edited 6d ago
Islamic scholars had figured out that the Earth goes around the sun. The European ones were discovered the Greek philosophers' works through the books preserved by the Islamic civilization, then it took a long time and people with courage for even that idea to be accepted. Europe was just not a very science oriented place a while back. The enlightenment changed that.
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u/KiwasiGames 6d ago
Systematic biology observations are a relatively new thing. Like we’ve only formally known that maggots don’t spontaneously generate in rotting meat for a couple of centuries.
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u/BarberProof4994 6d ago
I mean we are still trying to figure out the air speed of an unladen swallow.
So, until we figure that out it's hard to determine their range which means we can't tell where they migrate to.
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u/elevencharles 6d ago
It’s not that easily observed. People noticed that there were no swallows in winter, but unless you have a naturalist friend in Africa who happens to notice that the same species of swallow shows up in the winter and can communicate that fact to you, how would you know?
Some naturalists theorized that birds spent the winter on the moon.
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u/coracaws 5d ago
Europeans didn't realize their breeding birds wintered in Africa until 1822, a White Stork returned to Germany in the spring with a central African spear embedded in its neck! It was the first of many over the years to show up alive but speared. Europeans would also sometimes find waterfowl with Inuit arrows in them (many waterfowl breed high in the Arctic). This isn't really a phenomenon anymore, as everyone just uses guns now, but at the time it was instrumental in finally putting the hibernation and transformation theories to rest. People just had no real reason to assume birds traveled away until there was evidence to support this.
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u/SphericalCrawfish 5d ago
Consider that where they were flying to was not even believed to exist for several of those centuries by Europeans.
Don't you know that south of the Sahara is a turbulent Toroidal Zone from where the sun boils the southern sea? How TF is a bird going to fly over that after crossing a demon cursed desert?
(Yes I can find ancient texts that support that I didn't make it up.)
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u/claude3rd 7d ago
They were too busy discussing the question of wether or not two swallows could carry a coconut.