Clues to Homing Pigeon Navigation Mechanism

[BillTre]

TL;DR

Possible mechanism for homing pigeon navigation.

Animal navigation, long mysterious, may about to become better understood.
An unexpected mechanism in homing pigeons appears to sense magnetic fields and transmit the signal to the nervous system in ill defined way.
Ferritin containing macrophages were found in the liver near nerve cells which might transmit signals to the brain. Ferritin is a form of iron used to move it around in animal bodies in a controlled manner. The macrophages presumably get the ferritin when recycling old blood cell components. There are several not fully understood steps in this overall process.

There are three duct systems in the liver, artery, vein and bile duct. Nerves frequently run with blood vessels through the body. The macrophages are associated or close to the nerves.

Here is a Science summary article. It discusses how this was discovered and has a video of homing pigeon paths in various experimental conditions, such as pharmacological killing of the macrophages.
Here is the Science research article.

esearchers tested whether these iron-rich macrophages act as magnetic compasses for the pigeons through a simple, elegant experiment: knocking out the macrophages with a drug called clodronate liposomes. The team trained 34 homing pigeons, a variety bred for their skilled wayfinding, to fly a 19-kilometer route due east. During the day, pigeons use the position of the Sun to orient themselves. But when it’s cloudy and completely overcast, they rely on their magnetic sense to get their bearings. Near Lake Constance, the team injected 18 birds with clodronate and, 24 hours later, released them one by one when dense clouds completely blocked the Sun. The birds were outfitted with GPS transmitters, so the team could track the birds in real time.

Other proposed mechanisms include:

Exactly how this sense works has been hotly debated. An early hypothesis was that minute crystals of magnetite embedded within the animals’ tissues somehow act like compass needles. A more recent idea is that proteins in the retina, called cryptochromes, react to magnetic fields; this would allow migrating songbirds to fly in the right direction even in the dim glow of twilight. Last year, researchers studying homing pigeons discovered another mechanism. Laboratory experiments revealed that varying magnetic fields induces electric currents in their inner ears, stimulating nerves that lead to the brain. All 18 birds got hopelessly lost, only returning home after the skies had cleared. In contrast, 16 birds released after getting sham injections immediately flew straight home. “For me that was the first indication that there’s something really exciting going on,” Wikelski says. To rule out the possibility that the drug had disoriented the birds or caused other side effects to make them lose their way, the researchers released drugged birds on sunny days. They flew home just fine.

There will be more experiments to further characterize this.

 

[Hornbein]

Maybe I'm pulling rank but I learned of this in 1978. Further research showed quantum effects are also used to navigate. https://www.scientificamerican.com/article/how-migrating-birds-use-quantum-effects-to-navigate/

Here in Bali people are generally very good at knowing the direction of the points of the compass. I think it would be worthwhile to have a scientific test of this.

 

[256bits]

A more recent idea is that proteins in the retina, called cryptochromes, react to magnetic fields; this would allow migrating songbirds to fly in the right direction even in the dim glow of twilight
The birds should be able to fly home in the dim glow of moonlight, n'est pas, one would think, at least if there is a full moon where one is able to see quite well. Otherwise there is something about sunlight, and its effect upon the atmosphere or vice-versa that the birds use for navigation. Put some polarized glasses on the bird and see how it does in sunlight.

Even sugar in water will twist polarized light. Have the researchers tested for this effect with the cryptochrome proteins? If so, location of home and direction of flight towards home would come 'natural' for the bird to seek, regardless of season ( another thing to test ie perhaps light intensity as to when the migrating birds decide to take to flight ) as the bird lines up the light within the eye.

The researchers seem to be endlessly stuck on direct magnetic sensing rather than secondary effects.

 

[256bits]

Maybe I'm pulling rank but I learned of this in 1978. Further research showed quantum effects are also used to navigate. https://www.scientificamerican.com/article/how-migrating-birds-use-quantum-effects-to-navigate/

Here in Bali people are generally very good at knowing the direction of the points of the compass. I think it would be worthwhile to have a scientific test of this.

I can't read the SA article without a subscription - seems I went over my free limit reading articles in seismographs.

 

[Hornbein]

A more recent idea is that proteins in the retina, called cryptochromes, react to magnetic fields; this would allow migrating songbirds to fly in the right direction even in the dim glow of twilight
The birds should be able to fly home in the dim glow of moonlight, n'est pas, one would think, at least if there is a full moon where one is able to see quite well. Otherwise there is something about sunlight, and its effect upon the atmosphere or vice-versa that the birds use for navigation. Put some polarized glasses on the bird and see how it does in sunlight.

Even sugar in water will twist polarized light. Have the researchers tested for this effect with the cryptochrome proteins? If so, location of home and direction of flight towards home would come 'natural' for the bird to seek, regardless of season ( another thing to test ie perhaps light intensity as to when the migrating birds decide to take to flight ) as the bird lines up the light within the eye.

The researchers seem to be endlessly stuck on direct magnetic sensing rather than secondary effects.

It's possible to learn to see the polarization of light. This has been known since 1844. I've done it. The traditional method was looking at the sky after sunset. The light coming out of a LCD screen is polarized so with a white background it's easier to see.

https://en.wikipedia.org/wiki/Haidinger's_brush

As far as I know anyone can do it. It's always there but the brain normally filters it out as meaningless distraction. The simplest way is to look at that LCD screen and tilt your head side to side semirapidly. A faint yellow-golden color may appear for about a second then the brain filters it out again. With practice you can teach the brain that you want to see it and the full brush will appear. The brush is sort of a dirty gold shock of straw. It's neither pleasant nor unpleasant to look at and useless, so after I while I lost interest.

 

[256bits]

Tried it and it works!
Interesting.

 

[sbrothy]

Maybe I'm pulling rank but I learned of this in 1978. Further research showed quantum effects are also used to navigate. https://www.scientificamerican.com/article/how-migrating-birds-use-quantum-effects-to-navigate/

Here in Bali people are generally very good at knowing the direction of the points of the compass. I think it would be worthwhile to have a scientific test of this.

I was about to write something similar albeit a lot less secure. Something like:

It's certainly interesting that science is getting more and more sure, but didn't most scientists suspect (or, as @Hornbein mentioned, even know) that to be the case for a long time already (also with salmon and other animals who find their way back to their original birthplace (or lek).

 

[Bandersnatch]

Maybe I'm pulling rank but I learned of this in 1978. Further research showed quantum effects are also used to navigate. https://www.scientificamerican.com/article/how-migrating-birds-use-quantum-effects-to-navigate/

It's certainly interesting that science is getting more and more sure, but didn't most scientists suspect (or, as @Hornbein mentioned, even know) that to be the case for a long time already (also with salmon and other animals who find their way back to their original birthplace (or lek)

The point of the study is not to propose that birds can navigate via earth's magnetic field - that would be indeed trivial.
Rather, the study proposes a novel mechanism for how that is achieved biologically.

 

[sbrothy]

The point of the study is not to propose that birds can navigate via earth's magnetic field - that would be indeed trivial.
Rather, the study proposes a novel mechanism for how that is achieved biologically.

Oh I see. Sorry for my tendency to run with half the information. I stand corrected.

 

[BillTre]

Vikings were purported to use sunstones (Iceland spar, which has polarizing properties) for navigation at sea when clouds obscured the sun.