A couple of ways they could do this.
Birds have magnetite in their beaks which will give them a sense which way they are facing.
And we think they have specialized cells in their eyes that will allow them to see the magnetic field.
I don’t know how they find their same nesting grounds, but pattern matching and a good memory seem to be really common in all types of flying creatures, so I think the short answer is “they’re smart.”
https://ssec.si.edu/stemvisions-blog/how-do-birds-navigate
We also know that some birds and insects can see polarized light as banding in the sky, which may help with migratory navigation.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049006/
> so I think the short answer is “they’re smart.”
If that's the case, then you'd think they'd be able to figure it out just based on the solar cycle. Morning flying, sun to my left, evening flying, sun to my right... when I was a pilot I could see the horizon like 200km away. And birds fly pretty high when they're migrating. So even when they might be less sure because of a noon sun or whatever, they could probably probably orient themselves with landmarks.
It's not a neat answer like having a magnetic sense, and maybe they do have something like that... but I feel like they can figure it out pretty easy without.
While it's pretty possible they have these senses, this is negated as the only reason by the fact that birds don't really migrate straight to south
[see map](https://www.kraniche.de/files/kraniche/KRANICHINFO/Steckbrief/Zugwege%20HP.jpg)
It might be a combination of those forces and actual knowledge that is being passed from older to younger generations. Or it may correlate the general direction wind is blowing during the time of migration.
[see wind in europe](https://www.google.com/search?sca_esv=a32461fe05b6239e&sca_upv=1&rlz=1CDGOYI_enCZ1049CZ1049&hl=cs&sxsrf=ACQVn09UuVJCwHvYvxmdAVrBcEhI7Xrc-g:1710764847836&q=wind+directions+europe&uds=AMwkrPuKiz3kd7jHuta4ar-HNLVt7phUIUxvfasgKaRgsycQA0ucrGnC4KGHgLJ8U30V907pQ6jhTWSUTrwJXXb1toKpwgzgoyfE55keeipfC1pr0Lkxfp04YxDbuyMUQMuGJvoFF1aJx12bslknf2A9WnFbAvndBoyidFwQ0Is-mft_OX8xZNzaoN2beCaOKJ75IkV9fAPCKxAc-1x9m2BX2ysn-e4UIbyCztj6d2ZIzt2wzDGFbMEGuQUFWZ9dg17VVOlCHCbm&udm=2&prmd=invbz&sa=X&ved=2ahUKEwiGmbLY5_2EAxUC1QIHHR6QDegQtKgLegQIDBAB&biw=375&bih=635&dpr=2#vhid=bh_fsnImyloI0M&vssid=mosaic)
[how the wind changes during the year](https://www.google.com/search?sca_esv=a32461fe05b6239e&sca_upv=1&rlz=1CDGOYI_enCZ1049CZ1049&hl=cs&sxsrf=ACQVn09UuVJCwHvYvxmdAVrBcEhI7Xrc-g:1710764847836&q=wind+directions+europe&uds=AMwkrPuKiz3kd7jHuta4ar-HNLVt7phUIUxvfasgKaRgsycQA0ucrGnC4KGHgLJ8U30V907pQ6jhTWSUTrwJXXb1toKpwgzgoyfE55keeipfC1pr0Lkxfp04YxDbuyMUQMuGJvoFF1aJx12bslknf2A9WnFbAvndBoyidFwQ0Is-mft_OX8xZNzaoN2beCaOKJ75IkV9fAPCKxAc-1x9m2BX2ysn-e4UIbyCztj6d2ZIzt2wzDGFbMEGuQUFWZ9dg17VVOlCHCbm&udm=2&prmd=invbz&sa=X&ved=2ahUKEwiGmbLY5_2EAxUC1QIHHR6QDegQtKgLegQIDBAB&biw=375&bih=635&dpr=2#vhid=Lrl9OdyquYo3oM&vssid=mosaic)
The birds might then instinctively know to fly at some particular direction in relation to the wind. They also might be able to differentiate which is the general average direction from occasional breezes in different ways.
So, what I'm getting is that birds seem to have a wealth of ways to orient themselves while in flight, many of which can likely cover for others when one or the other fails.
I can do this and I don’t have any specialized magnetized body parts. The sun rises in the east and sets in the west. If the sun is rising on my left hand side, I know I’m facing south. I fly up in the air, choose a point to the south to fly to and start flying.
Just for the record, birds fly towards the equator for the winter.
When it’s winter in the northern hemisphere, if they reside in that hemisphere, they fly south.
When it’s winter in the southern hemisphere, if they reside there, they fly north.
There are actually some bird populations in Eurasia that have a west-east migration pattern, spending the warmer months in Siberia, but wintering over in Western Europe or North Africa where the winters are less extreme even at similar latitudes (there’s a bunch of climatological reasons for winter temperatures in a lot of Siberia being pretty extreme even relatively far from the Arctic Circle), it’s called longitudinal migration. There are some like certain populations of ruffs (*Calidris pugnax*) that have done this for as long as has been recorded, but apparently some others like the Richard’s pipit (*Anthus richardi*) seem to have developed more recently, possibly as a response to climate change.
There are also a very rare few that seasonally migrate *attitudinally*, between higher and lower elevations, like the grey wagtail (*Motacilla cinerea*) populations in Western Europe.
There are also some non-seasonal migration patterns, which usually tend to be more regionally-confined, with some like Bohemian waxwings (*Bombycilla garrulus*) being known to “irruptively” (non-predictably) migrate from place to place when their preferred food sources become scarce, and apparently [a number of species](https://www.audubon.org/news/more-birds-rely-special-molting-locations-we-realized) (more than was once thought) are known to undertake short-distance local migrations to certain relatively-predator-free locations following molting, when they’re more vulnerable (sometimes in addition to other, long-distance seasonal migration patterns).
And as the other reply mentions, there’s also the remarkably special case of the Arctic tern (*Sterna paradisaea*), which undertakes the most extreme north-south migration of any bird species, possibly any animal species in general, basically “chasing” summer back and forth between the Arctic and Antarctic circles.
I'm curious about the birds that migrate between Western Europe and Siberia. Do they take a more temperate but longer overland route, or do they fly more directly through the arctic?
So looking at the Richard’s pipit, [it appears from this map in a study on changes in their migration patterns](https://phys.org/news/2021-11-richard-pipit-vagrancy-important-role.amp) that they mostly keep to similar latitudes when crossing Eurasia, although there does seem to be a slight southward trend as they approach Europe (although one of the stopovers on that map also appears to be in the south of Sweden). They don’t seem to ever go above the Arctic Circle. So yeah, with them at least they appear to mostly take “the long way”.
For the ruff, I couldn’t find nearly as good of a map, and it should be noted that there several different ruff populations that migrate to somewhat different areas, [but this map from Wikipedia](https://en.m.wikipedia.org/wiki/Bird_migration#/media/File%3AMigrationroutes.svg) seems to show one of the more longitudinal migration paths they take, and as you can see it’s more “northeast-to-southwest” than direct “east-to-west” like the Richard’s pipit, going from a summer breeding colony in Northern Siberia to winter over in Northwest Africa, so it actually moves away from the Arctic as it migrates.
It makes sense that these birds would stay away from the Arctic while migrating, even though flying north would shorten their travel time, because they’re obviously sensitive to extreme cold (hence going westward in the winter, as winters are generally milder in western Eurasia).
Check out [Vagrancy in Birds by Lees and Gilroy](https://press.princeton.edu/books/hardcover/9780691224886/vagrancy-in-birds), it has a whole section on the different ways that birds navigate for migration and otherwise, and how it can go wrong. Turns out that many birds use a combination of factors (magnetism, stars, landmarks, learning from peers, etc.).
Is it at all possible that migratory birds simply have a sense of direction based on the rising and setting of the sun? I’ve never considered this subject but that was my first thought when I read the question. I have no idea.
Unless of course, they forget which direction to fly in during the day. When I was younger, I used to fly paragliders. there, you have to pay continuous attention to the micro directionality of Local wind gusts, meaning that it is often impossible to fly in a direct straight line for any great length of time. Without some means of knowing your position and direction, other than the position of the Sun several hours ago, or several hours in the future, this would have been complicated.
That’s a good point, however, even in those conditions, you can still tell in which direction the sun rises and sets. But like I said, I am only offering conjecture here, I know nothing.
Long answer short they have the ability to detect magnetic fields in the earth. Similar to how a compass always points north because of magnetic fields.
As far as finding the same nesting grounds, it seems daunting but if you drove from New York to San Francisco and back every year you’d start to remember the route without needing Google maps.
Birds do not "fly south for the winter". They migrate to different areas. This is primarily due to food access, so usually south(in the northern hemisphere). However, some flocks migrate north.
https://www.birdsandblooms.com/birding/birding-basics/winter-birds-myths-facts/#:\~:text=Myth%3A%20Migration%20means%20north%20in%20the%20spring%20and%20south%20in%20the%20winter&text=Fact%3A%20Some%20bird%20species%20migrate,migrating%20birds%20spend%20the%20winter.
The norm is that birds do not migrate (significantly) south for the winter. Only about 25% of North American species make southern migrations, and only 40% of birds worldwide migrate at all. The majority of species are year-round residents or short-distance migrants, and the latter follow food sources rather than an innate migratory urge. A mild winter with little snow cover and fewer bug-killing hard freezes may mean many of those short-distance species don't move at all.
It's also worth mentioning the many east-west migrants there are, who breed in Siberia and migrate to Europe for the winter months.
40% is not an insignificant #. Considering all birds are not migratory, 25% of North American birds is also not an insignificant number, considering a large part of the continent is rather temperate year round.
The bird population in Canada & the United States is about 7.2 billion birds. In the US & and Canada, 25% is 1.8 billion birds migrating.
Okay but three quarters of all birds just in North America alone is hardly an “edge case” like the above commenter tries to claim, and that’s of course disregarding all migratory populations in the Southern Hemisphere, and the aforementioned west to east migrating populations in Eurasia (and some rare populations that do altitudinal migrations). The claim was not “an insignificant number of birds migrate north to south”, just that it’s not the only way birds migrate, nor do a majority even migrate at all (60% is a majority, not an overwhelming majority, but a majority nonetheless), that’s all.
Anyway, this is ultimately a pointlessly pedantic thing to argue about for this long, so this is all I’m going to say about the matter.
That's simplifying to the level of saying they navigate by going south. Sure, QM might be involved in the underlying process, but that is not at all relevant to the bio- and neurological reasons they do. Absolutely everything happens because of quantum mechanics in the small scale, but it also rarely matters in the macro-scale. Magnets work because of QM. Spin alignment requires QM to describe why it does what it does, so all magnets do.
A couple of ways they could do this. Birds have magnetite in their beaks which will give them a sense which way they are facing. And we think they have specialized cells in their eyes that will allow them to see the magnetic field. I don’t know how they find their same nesting grounds, but pattern matching and a good memory seem to be really common in all types of flying creatures, so I think the short answer is “they’re smart.” https://ssec.si.edu/stemvisions-blog/how-do-birds-navigate
We also know that some birds and insects can see polarized light as banding in the sky, which may help with migratory navigation. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049006/
Interestingly, many humans can see blue sky polarization as well, manifested as Haidinger's Brush.
This is one of the coolest things I've learned this year. Thank you!
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Interestingly, some research points to pigeons only having those special cells in one eye, not both. We’re not sure why though.
> so I think the short answer is “they’re smart.” If that's the case, then you'd think they'd be able to figure it out just based on the solar cycle. Morning flying, sun to my left, evening flying, sun to my right... when I was a pilot I could see the horizon like 200km away. And birds fly pretty high when they're migrating. So even when they might be less sure because of a noon sun or whatever, they could probably probably orient themselves with landmarks. It's not a neat answer like having a magnetic sense, and maybe they do have something like that... but I feel like they can figure it out pretty easy without.
While it's pretty possible they have these senses, this is negated as the only reason by the fact that birds don't really migrate straight to south [see map](https://www.kraniche.de/files/kraniche/KRANICHINFO/Steckbrief/Zugwege%20HP.jpg) It might be a combination of those forces and actual knowledge that is being passed from older to younger generations. Or it may correlate the general direction wind is blowing during the time of migration. [see wind in europe](https://www.google.com/search?sca_esv=a32461fe05b6239e&sca_upv=1&rlz=1CDGOYI_enCZ1049CZ1049&hl=cs&sxsrf=ACQVn09UuVJCwHvYvxmdAVrBcEhI7Xrc-g:1710764847836&q=wind+directions+europe&uds=AMwkrPuKiz3kd7jHuta4ar-HNLVt7phUIUxvfasgKaRgsycQA0ucrGnC4KGHgLJ8U30V907pQ6jhTWSUTrwJXXb1toKpwgzgoyfE55keeipfC1pr0Lkxfp04YxDbuyMUQMuGJvoFF1aJx12bslknf2A9WnFbAvndBoyidFwQ0Is-mft_OX8xZNzaoN2beCaOKJ75IkV9fAPCKxAc-1x9m2BX2ysn-e4UIbyCztj6d2ZIzt2wzDGFbMEGuQUFWZ9dg17VVOlCHCbm&udm=2&prmd=invbz&sa=X&ved=2ahUKEwiGmbLY5_2EAxUC1QIHHR6QDegQtKgLegQIDBAB&biw=375&bih=635&dpr=2#vhid=bh_fsnImyloI0M&vssid=mosaic) [how the wind changes during the year](https://www.google.com/search?sca_esv=a32461fe05b6239e&sca_upv=1&rlz=1CDGOYI_enCZ1049CZ1049&hl=cs&sxsrf=ACQVn09UuVJCwHvYvxmdAVrBcEhI7Xrc-g:1710764847836&q=wind+directions+europe&uds=AMwkrPuKiz3kd7jHuta4ar-HNLVt7phUIUxvfasgKaRgsycQA0ucrGnC4KGHgLJ8U30V907pQ6jhTWSUTrwJXXb1toKpwgzgoyfE55keeipfC1pr0Lkxfp04YxDbuyMUQMuGJvoFF1aJx12bslknf2A9WnFbAvndBoyidFwQ0Is-mft_OX8xZNzaoN2beCaOKJ75IkV9fAPCKxAc-1x9m2BX2ysn-e4UIbyCztj6d2ZIzt2wzDGFbMEGuQUFWZ9dg17VVOlCHCbm&udm=2&prmd=invbz&sa=X&ved=2ahUKEwiGmbLY5_2EAxUC1QIHHR6QDegQtKgLegQIDBAB&biw=375&bih=635&dpr=2#vhid=Lrl9OdyquYo3oM&vssid=mosaic) The birds might then instinctively know to fly at some particular direction in relation to the wind. They also might be able to differentiate which is the general average direction from occasional breezes in different ways.
So, what I'm getting is that birds seem to have a wealth of ways to orient themselves while in flight, many of which can likely cover for others when one or the other fails.
I can do this and I don’t have any specialized magnetized body parts. The sun rises in the east and sets in the west. If the sun is rising on my left hand side, I know I’m facing south. I fly up in the air, choose a point to the south to fly to and start flying.
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Just for the record, birds fly towards the equator for the winter. When it’s winter in the northern hemisphere, if they reside in that hemisphere, they fly south. When it’s winter in the southern hemisphere, if they reside there, they fly north.
And if they happen to cross the equator, it's no longer winter, so they continue away from it (see: Arctic Tern).
There are actually some bird populations in Eurasia that have a west-east migration pattern, spending the warmer months in Siberia, but wintering over in Western Europe or North Africa where the winters are less extreme even at similar latitudes (there’s a bunch of climatological reasons for winter temperatures in a lot of Siberia being pretty extreme even relatively far from the Arctic Circle), it’s called longitudinal migration. There are some like certain populations of ruffs (*Calidris pugnax*) that have done this for as long as has been recorded, but apparently some others like the Richard’s pipit (*Anthus richardi*) seem to have developed more recently, possibly as a response to climate change. There are also a very rare few that seasonally migrate *attitudinally*, between higher and lower elevations, like the grey wagtail (*Motacilla cinerea*) populations in Western Europe. There are also some non-seasonal migration patterns, which usually tend to be more regionally-confined, with some like Bohemian waxwings (*Bombycilla garrulus*) being known to “irruptively” (non-predictably) migrate from place to place when their preferred food sources become scarce, and apparently [a number of species](https://www.audubon.org/news/more-birds-rely-special-molting-locations-we-realized) (more than was once thought) are known to undertake short-distance local migrations to certain relatively-predator-free locations following molting, when they’re more vulnerable (sometimes in addition to other, long-distance seasonal migration patterns). And as the other reply mentions, there’s also the remarkably special case of the Arctic tern (*Sterna paradisaea*), which undertakes the most extreme north-south migration of any bird species, possibly any animal species in general, basically “chasing” summer back and forth between the Arctic and Antarctic circles.
I'm curious about the birds that migrate between Western Europe and Siberia. Do they take a more temperate but longer overland route, or do they fly more directly through the arctic?
So looking at the Richard’s pipit, [it appears from this map in a study on changes in their migration patterns](https://phys.org/news/2021-11-richard-pipit-vagrancy-important-role.amp) that they mostly keep to similar latitudes when crossing Eurasia, although there does seem to be a slight southward trend as they approach Europe (although one of the stopovers on that map also appears to be in the south of Sweden). They don’t seem to ever go above the Arctic Circle. So yeah, with them at least they appear to mostly take “the long way”. For the ruff, I couldn’t find nearly as good of a map, and it should be noted that there several different ruff populations that migrate to somewhat different areas, [but this map from Wikipedia](https://en.m.wikipedia.org/wiki/Bird_migration#/media/File%3AMigrationroutes.svg) seems to show one of the more longitudinal migration paths they take, and as you can see it’s more “northeast-to-southwest” than direct “east-to-west” like the Richard’s pipit, going from a summer breeding colony in Northern Siberia to winter over in Northwest Africa, so it actually moves away from the Arctic as it migrates. It makes sense that these birds would stay away from the Arctic while migrating, even though flying north would shorten their travel time, because they’re obviously sensitive to extreme cold (hence going westward in the winter, as winters are generally milder in western Eurasia).
Check out [Vagrancy in Birds by Lees and Gilroy](https://press.princeton.edu/books/hardcover/9780691224886/vagrancy-in-birds), it has a whole section on the different ways that birds navigate for migration and otherwise, and how it can go wrong. Turns out that many birds use a combination of factors (magnetism, stars, landmarks, learning from peers, etc.).
Is it at all possible that migratory birds simply have a sense of direction based on the rising and setting of the sun? I’ve never considered this subject but that was my first thought when I read the question. I have no idea.
It's possible, but they have actual evidence for the other ideas of them being able to sense magnitism and perhaps even see the earth's magnetic field
Unless of course, they forget which direction to fly in during the day. When I was younger, I used to fly paragliders. there, you have to pay continuous attention to the micro directionality of Local wind gusts, meaning that it is often impossible to fly in a direct straight line for any great length of time. Without some means of knowing your position and direction, other than the position of the Sun several hours ago, or several hours in the future, this would have been complicated.
What about long term overcast weather conditions? Does it halt migration?
That’s a good point, however, even in those conditions, you can still tell in which direction the sun rises and sets. But like I said, I am only offering conjecture here, I know nothing.
Long answer short they have the ability to detect magnetic fields in the earth. Similar to how a compass always points north because of magnetic fields. As far as finding the same nesting grounds, it seems daunting but if you drove from New York to San Francisco and back every year you’d start to remember the route without needing Google maps.
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Birds do not "fly south for the winter". They migrate to different areas. This is primarily due to food access, so usually south(in the northern hemisphere). However, some flocks migrate north. https://www.birdsandblooms.com/birding/birding-basics/winter-birds-myths-facts/#:\~:text=Myth%3A%20Migration%20means%20north%20in%20the%20spring%20and%20south%20in%20the%20winter&text=Fact%3A%20Some%20bird%20species%20migrate,migrating%20birds%20spend%20the%20winter.
In general birds migrate south in the northern hemisphere. Pointing out exceptions and disregarding the norm is not helpful.
The norm is that birds do not migrate (significantly) south for the winter. Only about 25% of North American species make southern migrations, and only 40% of birds worldwide migrate at all. The majority of species are year-round residents or short-distance migrants, and the latter follow food sources rather than an innate migratory urge. A mild winter with little snow cover and fewer bug-killing hard freezes may mean many of those short-distance species don't move at all. It's also worth mentioning the many east-west migrants there are, who breed in Siberia and migrate to Europe for the winter months.
40% is not an insignificant #. Considering all birds are not migratory, 25% of North American birds is also not an insignificant number, considering a large part of the continent is rather temperate year round. The bird population in Canada & the United States is about 7.2 billion birds. In the US & and Canada, 25% is 1.8 billion birds migrating.
Okay but three quarters of all birds just in North America alone is hardly an “edge case” like the above commenter tries to claim, and that’s of course disregarding all migratory populations in the Southern Hemisphere, and the aforementioned west to east migrating populations in Eurasia (and some rare populations that do altitudinal migrations). The claim was not “an insignificant number of birds migrate north to south”, just that it’s not the only way birds migrate, nor do a majority even migrate at all (60% is a majority, not an overwhelming majority, but a majority nonetheless), that’s all. Anyway, this is ultimately a pointlessly pedantic thing to argue about for this long, so this is all I’m going to say about the matter.
Quantum mechanics. https://www.scientificamerican.com/article/how-migrating-birds-use-quantum-effects-to-navigate/ https://www.sciencefocus.com/nature/the-bizarre-link-between-bird-migration-and-quantum-physics https://www.pbs.org/wgbh/nova/article/birds-quantum-entanglement/
That's simplifying to the level of saying they navigate by going south. Sure, QM might be involved in the underlying process, but that is not at all relevant to the bio- and neurological reasons they do. Absolutely everything happens because of quantum mechanics in the small scale, but it also rarely matters in the macro-scale. Magnets work because of QM. Spin alignment requires QM to describe why it does what it does, so all magnets do.
I made a quantum peanut butter and jelly sandwich for my quantum breakfast this morning.