Evidence record

How do animals navigate?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

A judgement, not a fact: 3
Source checked: 40
Presented as open: 1

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A question in sensory biology. That birds and other animals use the Earth’s magnetic field is settled by behaviour; which cells and molecules detect it is not, and the two leading mechanisms are argued over largely by the groups that work on each.

Animals, birds among them, have a magnetic sense
Established
Controlled behavioural experiments since the 1960s, in many species, including reviewers who are sceptical of both leading mechanisms.
There is one mechanism to find
Contested
The page contrasts two mechanisms. Reviewers from the magnetite-sceptical side argue that animals may use more than one, for different parts of the field, and a third mechanism, electromagnetic induction, has also been proposed.
Navigating to a goal needs a map as well as a compass
Established
The map and compass framework is the field’s standard account; what the map is made of is the open part.

How the question is labelled

Claim: The compass nobody can find

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s title. It follows from the reviews cited here: the compass behaviour is established and the receptor cells have not been identified.

Context
Magnetoreception: a sense without a receptorAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Despite compelling behavioral evidence that this sense exists, the cells, molecules, and mechanisms that mediate sensory transduction remain unknown.

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: Navigation

Kind: Framing. Signposting. It asserts nothing a source could check.

The question

Claim: Birds sense the Earth’s magnetic field.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception: a sense without a receptorIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Although the existence of the sense can no longer be disputed, we understand little of the cells, molecules, and mechanisms that underlie it.
Supports
Magnetoreception in birdsAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Birds can use two kinds of information from the geomagnetic field for navigation: the direction of the field lines as a compass and probably magnetic intensity as a component of the navigational ‘map’.

Later work looked for

Europe PMC, 2019 on, avian magnetic compass behaviour: the 2022 review and later radiofrequency studies treat the inclination compass and its light dependence as established; nothing that changes it.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: After sixty years of looking, the cells that do it have not been identified.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Sixty years counts from the first demonstration in robins, published in 1965.

Supports
Myths in magnetosensationIntroduction, and “It has to be cryptochrome”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: The breakthrough experiment came in 1965 when Wolfgang Wiltschko, a doctoral student in the group of Friedrich Merkel, published the first compelling experimental evidence for a magnetic sense in European robins ... or which cells would function as the primary sensors
Supports
Magnetoreception: a sense without a receptor“A light-sensitive chemical-based compass”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Moreover, we still don’t know which cells are associated with a light-dependent chemical compass.
Supports
Magnetoreception in birdsSection 3.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Presently, the specific location of the magnetite-based magnetoreceptors is still unclear.

What this does not establish

The eye is widely taken to be where the compass sits; what has not been found is the receptor cells, in the eye or elsewhere.

Later work looked for

Europe PMC, 2023 to 2026, magnetoreceptor or cryptochrome in birds: in vitro and computational papers only; no receptor cell identified in any bird.

Corrected

24 September 2026. Previously: “After sixty years of looking, the organ that does it has not been identified.” The reviews put the compass in the eye; what is unidentified is the receptor cells. “The organ” overstated the gap.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: Magnetic sensing in migratory birds is demonstrated behaviourally beyond doubt.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception: a sense without a receptorAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Despite compelling behavioral evidence that this sense exists, the cells, molecules, and mechanisms that mediate sensory transduction remain unknown.
Supports
Myths in magnetosensationSummary
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: A series of elegant behavioral experiments in the 1960s and 1970s showed conclusively that the sense is real

Later work looked for

Europe PMC, 2019 on, avian magnetic compass behaviour: the 2022 review and later radiofrequency studies treat the inclination compass and its light dependence as established; nothing that changes it.

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: The mechanism has a leading candidate involving quantum-scale chemistry in the eye, and the sensory cells themselves have not been found.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensation“It has to be cryptochrome”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Consequently, CRY4 is rightly considered to be the best candidate magnetoreceptor in birds
Supports
Magnetoreception: a sense without a receptor“A light-sensitive chemical-based compass”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Although it is widely assumed that the primary sensors reside in the retina, no report has convincingly shown that a particular cell type (e.g., cones) is sensitive to magnetic stimuli.
Context
The Radical-Pair Mechanism of MagnetoreceptionAbstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Theory · Review of the field
The source reads: The leading hypothesis centers on radical pairs–magnetically sensitive chemical intermediates formed by photoexcitation of cryptochrome proteins in the retina.

What this does not establish

“Leading” is a judgement of the field’s reviews, not a demonstration: the candidate has not been shown to work in a living bird.

Later work looked for

Europe PMC, 2021 on, cryptochrome and magnetoreception in birds: in vitro, structural and computational work on robin cryptochrome 4 (among them a 2025 paper finding cryptochrome 4b probably irrelevant), and nothing showing a cryptochrome acting as a magnetoreceptor in a living bird.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: Young songbirds raised indoors, which have never migrated or seen the sky, will orient in a cage in their species’ migratory direction.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Do first-time avian migrants know where they are going: the clock-and-compass concept todayFigure 5 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Experiment
The source reads: Birds from 3 days of age were kept indoors without access to natural celestial cues, hand-fed, and tested in Emlen funnels in the fall, in a natural magnetic field and without access to stars.
Supports
Do first-time avian migrants know where they are going: the clock-and-compass concept today“Clock-and-compass concept”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Gwinner and Wiltschko (1978) showed that hand-reared garden warblers Sylvia borin from Germany followed an innate sequence of orientation behaviors when tested in circular arenas, which corresponds to the flight directions of their free-living counterparts.
Context
Magnetoreception in birdsSection 3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Migrants additionally acquire the respective knowledge on the ‘map’ factors for their extended journeys during their first migration, which is controlled by an innate migration programme

What this does not establish

A result for songbirds such as pied flycatchers and garden warblers, tested in funnels and arenas. That the magnetic field is what they use in these tests is the inference of the wider literature, not a claim this caption makes.

Later work looked for

Europe PMC, open access, naive or hand-raised birds and the magnetic compass: the 2025 review, now cited, is the most recent account; nothing that changes it.

Corrected

24 September 2026. Previously: “A young bird that has never migrated will orient in the correct direction on its first attempt, in a cage, with no view of the sky.” The result is a group mean with individual scatter, not every bird on its first attempt, and it is shown in songbirds raised indoors. The page cited no source for it; a 2025 review was added.

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: Not every bird gets it right, but the group does.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Do first-time avian migrants know where they are going: the clock-and-compass concept todayFigure 5 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Experiment
The source reads: N = 35, mean direction 178° (r = 0.42, P = 0.002) ... The dots at the periphery of the circle represent the mean heading of a single bird, the arrow represents the group orientation mean vector

What this does not establish

The group vector length of 0.42 in the autumn test means individual headings scatter widely around the mean.

Later work looked for

Europe PMC, open access, naive or hand-raised birds and the magnetic compass: nothing that changes it.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: The behaviour is not in question.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensationIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: The important question is no longer: Do animals detect the Earth’s magnetic field? But rather: How do animals detect magnetic fields?

Later work looked for

Europe PMC, 2019 on, avian magnetic compass behaviour: the 2022 review and later radiofrequency studies treat the inclination compass and its light dependence as established; nothing that changes it.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: What it is using has been argued about since the 1960s.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensationSummary
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: A series of elegant behavioral experiments in the 1960s and 1970s showed conclusively that the sense is real; however, the underlying mechanism(s) remained unresolved.

Claim 10 · checked 24 September 2026 · AI-assisted audit

What the sense does

Claim: What the sense does

Kind: Framing. Signposting. It asserts nothing a source could check.

The sense exists and has odd properties

Claim: The sense exists and has odd properties

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsSection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Behavioural experiments, mostly based on the orientation of migratory birds, revealed three surprising characteristics of the avian magnetic compass

Later work looked for

Europe PMC, 2019 on, avian magnetic compass behaviour: the 2022 review and later radiofrequency studies treat the inclination compass and its light dependence as established; nothing that changes it.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: Birds tested in controlled magnetic fields shift their preferred direction when the field is shifted.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensationIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Merkel and Wiltschko showed that altering the magnetic environment leads to a deflection of the preferred migratory direction (Merkel and Wiltschko, 1965).
Supports
Magnetoreception: a sense without a receptorIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: By using small circular arenas they modified the preferred direction of orientation during migratory restlessness by the application of artificial magnetic fields

Later work looked for

Europe PMC, 2019 on, avian magnetic compass behaviour: the 2022 review and later radiofrequency studies treat the inclination compass and its light dependence as established; nothing that changes it.

Corrected

24 September 2026. Previously: “Birds tested in controlled magnetic fields orient according to the field rather than to any other cue.” The experiments show that changing the field changes the bird’s heading. They do not show that birds ignore other cues, which they also use.

Claim 13 · checked 24 September 2026 · AI-assisted audit

Claim: The sense responds to the inclination of the field rather than its polarity, so it distinguishes poleward from equatorward rather than north from south.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsSection 2, property 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: It is an inclination compass, not sensitive to the polarity of the magnetic field ... It thus does not distinguish between magnetic North and South, but between ‘poleward’, where the field lines run downward, and ‘equatorward’, where they run upward.
Supports
Myths in magnetosensationIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: robins do not rely on the polarity of the magnetic vector for orientation, but rather the inclination of the field with respect to the surface of the Earth (Wiltschko and Wiltschko, 1972)

What this does not establish

A property of the bird compass. Fish and mammals tested so far have a polarity compass instead.

Later work looked for

Europe PMC, 2019 on, avian magnetic compass behaviour: the 2022 review and later radiofrequency studies treat the inclination compass and its light dependence as established; nothing that changes it.

Claim 14 · checked 24 September 2026 · AI-assisted audit

Claim: It depends on light, and on specific wavelengths: under yellow or red light, or in darkness, the normal compass orientation fails.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsSection 2, property 3; section 3.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: It requires short-wavelength light. Tests under near-monochromatic lights revealed that orientation is possible under light from ultraviolet to about 565 nm green; under yellow and red light, birds are disoriented ... the normal inclination compass appears to be disrupted, such as total darkness

What this does not establish

In darkness and some unnatural lights birds show a different, “fixed direction” response, which the same review attributes to receptors in the beak; the normal migratory compass is what fails.

Later work looked for

Europe PMC, 2019 on, avian magnetic compass behaviour: the 2022 review and later radiofrequency studies treat the inclination compass and its light dependence as established; nothing that changes it.

Corrected

24 September 2026. Previously: “It depends on light, and on specific wavelengths: in darkness or under long-wavelength light, the orientation fails.” Birds in darkness are not simply disoriented: they show a fixed-direction response. What fails is the normal compass.

Claim 15 · checked 24 September 2026 · AI-assisted audit

Claim: These are the properties that led Ritz and colleagues to propose a chemical mechanism.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsSection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: These properties of the avian magnetic compass caused Ritz and colleagues [15] to propose the radical pair model

Corrected

24 September 2026. Previously: “A compass built from a magnetised particle would not behave that way, and that observation is what made a chemical mechanism plausible.” That a particle compass could not behave this way is contested by the researchers who work on particles (claim 17). The sourced part is that these properties prompted the radical-pair proposal.

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: Proponents of magnetic particles reply that an inclination compass does not tell the two apart, and offer other explanations for the light dependence.

Kind: Disputed. A contested point, where the page reports a side or the disagreement.
Review: Source checked. The cited passage was read, and it says this.

Supports
Biophysics of magnetic orientation: strengthening the interface between theory and experimental designSection 4.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: In view of this, the observation of inclination-only magnetic compass responses in many animals does not help to distinguish between a magnetite-based system and one using radical pairs.
Supports
Biophysics of magnetic orientation: strengthening the interface between theory and experimental designAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: We also propose new experiments to confirm whether or not animals can detect magnetic fields using the radical-pair effect together with an alternate hypothesis that may explain the dependence on light of responses
Cuts against
Magnetoreception in birdsSection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: This model is in agreement with the known characteristics of the avian magnetic compass.

Other readings

The 2019 review, from the group that described these properties, reads them as fitting the chemical model, and assigns magnetite a different job in birds.

Corrected

24 September 2026. Previously: “” The page presented the properties as ruling out a particle compass without saying that its proponents dispute it.

Claim 17 · checked 24 September 2026 · AI-assisted audit

The leading candidate is chemical

Claim: The leading candidate is chemical

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensation“It has to be cryptochrome”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: At present, CRY4 is the only credible suspect, but it is conceivable that another will emerge whose photonic fingerprint better fits the profile.
Supports
Magnetoreception in birdsSection 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: At present, the findings indicate that birds sense magnetic directions by radical pair processes in the eye

What this does not establish

Leading for the compass. For a sense of field intensity, magnetite is still the main proposal.

Later work looked for

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: Absorbing a photon in a molecule called cryptochrome, present in the retina, can produce a pair of radicals inside the protein, with their electron spins either opposed or aligned.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetic sensitivity of cryptochrome 4 from a migratory songbirdPublished abstract; main text, first paragraph after the abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: cryptochrome flavoproteins located in the retinas of the birds ... radical pairs in cryptochromes are formed via sequential electron hopping along a chain of three or four tryptophans
Supports
Magnetoreception in birdsSections 2.1 and 2.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: upon absorption of a photon, radical pairs are formed, either as singlets with antiparallel spin or as triplets with parallel spin ... Four types of cryptochromes–Cry1a, Cry1b, Cry2 and Cry4–have been found in the eyes of birds.

What this does not establish

That this happens in cryptochrome in the test tube is measured. That it is how a bird senses the field is the hypothesis.

Corrected

24 September 2026. Previously: “Absorbing a photon in a molecule called cryptochrome, present in the retina, can produce a pair of molecules each carrying an unpaired electron.” The radical pair forms within the one protein, between its flavin and a tryptophan, not as two separate molecules.

24 September 2026. Previously: “Absorbing a photon in a molecule called cryptochrome, present in the retina, can produce a pair of radicals inside the protein, each carrying an unpaired electron.” No source read says the radicals each carry an unpaired electron; the 2019 review describes the pair as formed with antiparallel or parallel spins, and the sentence now says that.

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: The two electron spins are linked, and a magnetic field can influence how that linkage evolves, which changes the proportions of the products of the reaction.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetic sensitivity of cryptochrome 4 from a migratory songbirdMain text, first paragraph after the abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: The radical pair mechanism is a well-established source of ... field effects on the rates and yields of chemical reactions
Supports
Magnetoreception in birdsSection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: The ratio between the two states depends on the orientation of the radical pair in the magnetic field and can thus mediate magnetic directions.

What this does not establish

The chemistry is established; whether a bird reads its outcome is not (claim 30).

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: The effect is tiny and the Earth’s field is weak, but a model radical pair has been shown to respond to the direction of an Earth-strength field

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetic sensitivity of cryptochrome 4 from a migratory songbirdMain text, first paragraph after the abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: Proof-of-principle experiments have demonstrated the sensitivity of a model radical pair system to the direction of an Earth-strength magnetic field

What this does not establish

A model chemical system in the laboratory, not cryptochrome and not a bird. The paper cites the experiments rather than reporting them.

Later work looked for

Corrected

24 September 2026. Previously: “The effect is tiny and the Earth’s field is weak, but the chemistry is sensitive enough in principle, and the wavelength dependence and the inclination compass both fall out of it naturally.” “In principle” is replaced with what was shown, and “fall out of it naturally” overstated the fit: a 2022 review names two problems the mechanism has not answered, and the page now says so.

Claim 21 · checked 24 September 2026 · AI-assisted audit

Claim: and the mechanism accounts for the inclination compass and the need for light.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsSection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Because the singlet/triplet ratio depends on the course of the field lines, but not on their polarity, it results in an inclination compass, as found in birds.

Other readings

Researchers who work on magnetite argue that a particle compass can also act as an inclination compass (claim 17), and a 2022 review finds the fit with green light poor (claim 23).

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: Critics point to what it has not answered: how a signal a million times smaller than the thermal energy around it is read in a living cell, and how birds orient under green light, outside the range absorbed by the form of the molecule that starts the reaction.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensation“It has to be cryptochrome”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: There is a notable inconsistency between the absorption spectra of the fully oxidized FAD ... and the ability of birds to orient in green light (565 nm) ... The energy resulting from this thermal background is more than a million times stronger than the effect of a 50 μT field
Qualifies
Magnetoreception in birdsSection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Cryptochrome, the suggested magneto-receptor molecule, absorbs short-wavelength light from UV to about 560 nm

Other readings

The 2019 review holds that cryptochrome’s absorption, counting its other forms, does match the wavelengths birds orient under.

Corrected

24 September 2026. Previously: “” Added, see claim 21.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: In 2021 cryptochrome 4 from the European robin was shown to be magnetically sensitive in a test tube, and more so than the same protein from chicken and pigeon, in a field of 30 millitesla, several hundred times the Earth’s.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetic sensitivity of cryptochrome 4 from a migratory songbirdPublished abstract; main text on figure 2c
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: Here we show that the photochemistry of cryptochrome 4 (CRY4) from the night-migratory European robin (Erithacus rubecula) is magnetically sensitive in vitro, and more so than CRY4 from two non-migratory bird species, chicken (Gallus gallus) and pigeon (Columba livia). ... caused by a 30 mT magnetic field
Purified protein in solution.
Supports
Myths in magnetosensation“It has to be cryptochrome”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: recent studies have shown that CRY4 has the capacity to form long-lived radical pairs which are susceptible to magnetic fields (30 mT) ... The Earth’s magnetic field is very small (50 μT)

What this does not establish

Thirty millitesla against about fifty microtesla is some six hundred times the Earth’s field. The authors do not expect the free protein to respond to an Earth-strength field without partners that anchor and align it, none of which is known.

Later work looked for

Corrected

24 September 2026. Previously: “In 2021 the cryptochrome of the European robin was shown to be magnetically sensitive in a test tube, and more so than the same protein from chicken and pigeon.” The page did not say which cryptochrome, or that the measurements were made in a field far stronger than the one a bird navigates by.

Claim 24 · checked 24 September 2026 · AI-assisted audit

Claim: That is not the same as demonstrating it in a bird, and its authors say so.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetic sensitivity of cryptochrome 4 from a migratory songbirdFinal paragraph of the main text
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: To know whether Cry4 is the magnetoreceptor molecule in vivo, direct manipulations of this protein in the eyes of night-migratory songbirds would be required.

Corrected

24 September 2026. Previously: “That is not the same as demonstrating it in a bird.” Attributes the caution to the paper, which states it.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: Two leading mechanisms, both still live

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception: a sense without a receptorHow might animals detect the magnetic field?
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Currently, there are 3 dominant hypotheses that are being tested. The first predicts that magnetic fields are detected by a mechanically sensitive magnetite-based magnetoreceptor. The second hypothesis relies on a light-sensitive, chemical-based mechanism
Supports
Biophysics of magnetic orientation: strengthening the interface between theory and experimental designAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Subsequent identification of at least two plausible biophysical mechanisms for magnetoreception in animals, one based on biogenic magnetite and another on radical-pair biochemical reactions

What this does not establish

A third proposal, electromagnetic induction, is also being tested, and reviewers argue the mechanisms are not mutually exclusive.

Corrected

24 September 2026. Previously: “Two mechanisms, both still live” A 2017 review counts three dominant hypotheses; these are the two the page compares.

Claim 26 · checked 24 September 2026 · AI-assisted audit

Claim: Radical pairs in the eye

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: The direction of the magnetic field appears to be sensed via radical pair processes in the eyes, with the crucial radical pairs formed by cryptochrome.

What this does not establish

Proposed, with support; not demonstrated in a living bird.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: Fits the light dependence and the inclination compass, though critics question the fit under green light

Kind: Disputed. A contested point, where the page reports a side or the disagreement.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsSection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: This model is in agreement with the known characteristics of the avian magnetic compass.
Supports
Myths in magnetosensation“It has to be cryptochrome”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: There is a notable inconsistency between the absorption spectra of the fully oxidized FAD (320–500 nm) (Evans et al., 2013) which is necessary for radical formation, and the ability of birds to orient in green light (565 nm)

Other readings

The 2019 review sees no inconsistency with green light; the 2022 review does. Researchers on magnetite add that the inclination compass does not discriminate (claim 17).

Corrected

24 September 2026. Previously: “Explains the light dependence and the inclination compass” The fit is disputed; see claims 17 and 23.

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: Magnetic sensitivity shown in purified protein, in fields far stronger than the Earth’s

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetic sensitivity of cryptochrome 4 from a migratory songbirdPublished abstract; main text on figure 2c
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: is magnetically sensitive in vitro ... caused by a 30 mT magnetic field

What this does not establish

See claim 24.

Later work looked for

Corrected

24 September 2026. Previously: “Chemistry demonstrated in purified protein” The field strength of the test matters to what it shows; see claim 24.

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: No cell has been shown to use it for sensing in a living animal

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception: a sense without a receptor“A light-sensitive chemical-based compass”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Although it is widely assumed that the primary sensors reside in the retina, no report has convincingly shown that a particular cell type (e.g., cones) is sensitive to magnetic stimuli.
Supports
Myths in magnetosensation“It has to be cryptochrome”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: it is not immediately clear how the animal would distinguish between a visual and magnetic stimulus, or which cells would function as the primary sensors

Later work looked for

Europe PMC, 2023 to 2026, magnetoreceptor or cryptochrome in birds: in vitro and computational papers only; no receptor cell identified in any bird.

Claim 30 · checked 24 September 2026 · AI-assisted audit

Claim: Magnetic particles

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Organisms make magnetite, and crystals of the right size could transduce a field directly

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception: a sense without a receptor“A mechanically sensitive magnetite-based magnetoreceptor”, and figure caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: This conceptually simple idea is tenable because it is known that a number of species are able to form biogenic magnetite. ... This linear arrangement of single-domain crystals attempts to align with the Earth's geomagnetic field (like a compass needle), and thereby exerts a torque force on a mechanosensitive channel
Supports
Biophysics of magnetic orientation: strengthening the interface between theory and experimental designSection 4.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Magnetite biomineralization is a well-known phenomenon ... Subsequent biophysical analyses have shown that biogenic magnetite is a viable mechanism for magnetoreception

What this does not establish

That organisms make magnetite is established. That a vertebrate uses it in a sensory cell has not been shown.

Corrected

24 September 2026. Previously: “Iron minerals are found in some tissues and could transduce a field directly” Iron is found in many tissues, which is part of the problem; the argument is about magnetite crystals of a particular size.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: In birds, usually proposed for a map sense of intensity rather than the compass

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: the direction of the field lines as a compass and probably magnetic intensity as a component of the navigational ‘map’. ... Magnetic intensity appears to be perceived by magnetite-based receptors in the beak region
Qualifies
Biophysics of magnetic orientation: strengthening the interface between theory and experimental designSection 4.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: a magnetite-based compass magnetoreceptor system permits a species to have a compass that operates in either a polar or axial (inclination) mode

Corrected

24 September 2026. Previously: “Would suit a map sense of magnitude rather than a compass of direction” Researchers on magnetite argue it could serve a compass too; in birds it is the intensity map that it is usually proposed for.

Claim 33 · checked 24 September 2026 · AI-assisted audit

Claim: Critics find that claimed receptor cells have turned out to be immune cells or laboratory contamination

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception: a sense without a receptor“A mechanically sensitive magnetite-based magnetoreceptor”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Macrophages have been mistaken for magnetoreceptors [20,21], iron contamination from the laboratory environment has led investigators astray [22–24]

Other readings

The 2019 review, from the group that holds that beak receptors exist, disputes part of the macrophage finding (claim 38).

Corrected

24 September 2026. Previously: “Claimed receptor cells have repeatedly turned out to be contamination or other structures” Attributed to the critics who report it, since the finding is disputed, and made specific.

Claim 34 · checked 24 September 2026 · AI-assisted audit

What performs it

Claim: What performs it

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Sixty years of looking for the receptor cells, and they could be almost anywhere in the body.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensationIntroduction, and “It has to be cryptochrome”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: The breakthrough experiment came in 1965 when Wolfgang Wiltschko, a doctoral student in the group of Friedrich Merkel, published the first compelling experimental evidence for a magnetic sense in European robins ... or which cells would function as the primary sensors
Supports
Magnetoreception: a sense without a receptorBox 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: magnetic fields can freely penetrate biological tissue, and therefore magnetoreceptive systems could be located in any tissue in an animal’s body, literally from head to toe

What this does not establish

A possibility the reviews raise, not a finding. The chemical account places its receptors in the retina.

Corrected

24 September 2026. Previously: “Sixty years of looking for an organ, and the best candidate may not need one.” The leading candidate is placed in the eye, so it does not dispense with an organ; what the reviews say is that the receptor cells could be anywhere.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Where the receptor is

Claim: Where the receptor is

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Several candidate receptor cells have been reported and then reinterpreted.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensation“It has to be magnetite”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Anatomical regions of interest have included the olfactory epithelium of trout (Walker et al., 1997; Eder et al., 2012), the abdomen of honeybees (Kuterbach et al., 1982), the upper beak skin of pigeons
Supports
Magnetoreception in birdsSection 3.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Yet their possible function as magnetoreceptors was questioned as they seemed unsuitable to provide magnetic information

Later work looked for

Europe PMC, 2013 on, magnetite or iron-rich cells as vertebrate magnetoreceptors: a 2015 study finding no intracellular magnetite in cells picked out by magnetic screening, and the 2017 and 2022 reviews now cited here; no magnetite receptor has been confirmed.

Corrected

24 September 2026. Previously: “Several candidate receptor cells have been reported and then withdrawn or reinterpreted, including a widely cited claim that was traced to iron-rich immune cells rather than neurons.” No source read shows a claim withdrawn by its authors. The 2012 study’s abstract says “widely accepted”, not “widely cited”, and its finding is disputed by the group that holds beak receptors exist, which the page now says.

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: The best known, magnetite-bearing nerve endings in the pigeon’s upper beak, had been widely accepted in the field until a 2012 study identified the iron-rich cells there as macrophages, immune cells rather than neurons.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Myths in magnetosensation“Birds have a conserved six loci magnetic sense system in their upper beak”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Hypothesizing that these cells were really macrophages, we undertook immunostaining with the antigen-presenting marker MHCII and CD44, revealing high levels of co-localization (≈95%) (Treiber et al., 2012, 2013)
Context
Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neuronsAbstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in animals · Experiment
The source reads: magnetite-containing trigeminal afferents located at six specific loci in the rostral subepidermis of the beak ... These studies have been widely accepted in the field ... clusters of iron-rich cells in the rostro-medial upper beak of the pigeon Columbia livia are macrophages, not magnetosensitive neurons.

What this does not establish

The 2012 study is read here only as its abstract; its methods are described in its authors’ 2022 review.

Later work looked for

Claim 39 · checked 24 September 2026 · AI-assisted audit

Claim: Supporters of receptors in the beak still dispute parts of that reading.

Kind: Disputed. A contested point, where the page reports a side or the disagreement.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsSection 3.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Also, in contrast to the authors mentioned above, they failed to find magnetite in the upper beak; yet, they used the spinning field method [113], which works well for single domains, but not for superparamagnetic particles.
Qualifies
Myths in magnetosensation“Birds have a conserved six loci magnetic sense system in their upper beak”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: We think the myth of a 6 loci magnetic sense system in birds can now be put to rest, but what of a trigeminal-mediated magnetic sense?

Other readings

The 2022 review, from the group that did the 2012 study, holds that the six-site beak system “can now be put to rest”, while leaving open a trigeminal magnetic sense elsewhere.

Claim 40 · checked 24 September 2026 · AI-assisted audit

Claim: A sense whose receptors cannot be located after this long is unusual.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s judgement, which the 2017 review shares in its own words.

Context
Magnetoreception: a sense without a receptorBox 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: It is astonishing that 50 years have passed since the seminal behavioral experiments of Wiltschko and colleagues, and still our mechanistic understanding of this sense remains rudimentary.

Corrected

24 September 2026. Previously: “A sense whose organ cannot be located after this long is unusual.” The search is for receptor cells; see claim 4.

Claim 41 · checked 24 September 2026 · AI-assisted audit

Claim: Part of the reason may be that magnetic fields pass through tissue: nothing like a lens or an ear is needed to gather the stimulus, so the receptor cells could lie almost anywhere in the body, with no organ to point to them.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Biophysics of magnetic orientation: strengthening the interface between theory and experimental designSection 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Because magnetic fields pass through tissue, no accessory structure such as a lens or ear canal is required to bring the external magnetic field inside the body and project it onto a sensory epithelium. ... An accessory sensory structure, however, invites structural study and facilitates the identification of a mechanism
Supports
Magnetoreception: a sense without a receptorBox 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: magnetic fields can freely penetrate biological tissue, and therefore magnetoreceptive systems could be located in any tissue in an animal’s body, literally from head to toe

Corrected

24 September 2026. Previously: “It is also consistent with a mechanism that requires no specialised organ, which is one reason the chemical account is attractive.” The chemical account places its receptors in the eye, and the no-organ argument is made by researchers on both sides, including those who work on magnetite. No source read gives it as a reason to prefer the chemical account.

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: Each account’s case is made mostly by the people who work on it, and the two camps have become entrenched, which is worth knowing when they are weighed against each other.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The sources cited in this passage bear it out: the 2010 paper is by researchers on magnetite, the 2012 study and the 2017 and 2022 reviews by its critics, and the 2016 and 2021 papers by the chemical account’s main proponents.

Context
Myths in magnetosensationConcluding remarks
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: At conferences, cryptochrome has often faced magnetite on the scientific battlefield, with views becoming more deeply entrenched.

Corrected

24 September 2026. Previously: “The case for the other mechanism is made by the people who work on it rather than by the people who work on the first, which is worth knowing when the two are weighed against each other.” The original implied an asymmetry the sources do not show: the chemical account’s case is also made chiefly by its own researchers.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: The magnetite account’s proponents argue that biogenic magnetite is demonstrably made by organisms, that crystals of the right size and arrangement would transduce a field directly, and that the absence of a confirmed receptor is a statement about how hard these cells are to find.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Biophysics of magnetic orientation: strengthening the interface between theory and experimental designSections 4 and 4.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Magnetite biomineralization is a well-known phenomenon ... Magnetite crystals perfectly suited for magnetoreception have been found in all domains of living organisms except the Archaea ... An accessory sensory structure, however, invites structural study and facilitates the identification of a mechanism
Context
Magnetite-based magnetoreceptionAbstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in animals · Review of the field
The source reads: Across many species and groups of organisms, compelling evidence exists that the physical basis of this response is tiny crystals of single-domain magnetite (Fe3O4).

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: Its critics reply that the search has been led astray by immune cells and by iron contamination from the laboratory itself.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception: a sense without a receptor“A mechanically sensitive magnetite-based magnetoreceptor”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Macrophages have been mistaken for magnetoreceptors [20,21], iron contamination from the laboratory environment has led investigators astray [22–24]
Supports
Myths in magnetosensation“It has to be magnetite”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: The laboratory serves as a fertile source of magnetic material whether it be from glassware, dissection tools, or histological blades

Corrected

24 September 2026. Previously: “” The passage stated the magnetite case in its proponents’ terms and the reply only in the module. Both sides are now in the prose.

Claim 45 · checked 24 September 2026 · AI-assisted audit

How the map works

Claim: How the map works

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: A compass gives direction.

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Getting to a specific place requires knowing where you are, and displaced birds can correct for it, which implies a map as well.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Magnetoreception in birdsSection 3.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: Most interesting are studies where migrants were displaced, either in reality or virtually by simulating the magnetic field conditions of a distant region. The birds compensated for the displacement and changed their course accordingly
Supports
Map and compass navigation: the mechanism and ontogeny of animal mapsMap structure
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: ‘migratory true navigation’, the ability to correct or compensate for displacements from a migratory trajectory
Qualifies
Do first-time avian migrants know where they are going: the clock-and-compass concept today“Clock-and-compass concept”; “Criticism of the clock-and-compass concept”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: young migrants follow a spatio-temporal program, while adults possess a bicoordinate map that allows them to correct for natural or artificial displacements ... Young individuals of some bird species indeed possess innate orientation abilities and elements of a navigational map.

What this does not establish

Shown mainly in experienced adults. The classic view is that young birds on their first migration follow an inherited programme rather than a map, though the young of some species show elements of one.

Later work looked for

Europe PMC, 2018 on, displacement experiments in migratory birds: the 2025 review now cited; nothing that changes it.

Claim 48 · checked 24 September 2026 · AI-assisted audit

Claim: Candidate map cues include magnetic intensity and inclination, smell and landmarks, and more speculatively infrasound.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Map and compass navigation: the mechanism and ontogeny of animal mapsMap cues
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: map cues perceived through three sensory modalities: magnetic, visual and olfactory cues ... magnetic inclination ... magnetic intensity ... map information from landmark features ... various other sources of map cues have been suggested, including ... infrasound ... However, there is currently relatively limited evidence in the form of controlled experiments

Corrected

24 September 2026. Previously: “Candidate map cues include magnetic intensity and inclination, smell, and infrasound. Evidence exists for each in some species, and no general account covers the range of animals that do this.” A 2025 review finds relatively limited controlled evidence for infrasound as a map cue, so it is not on a par with the others; visual landmarks were missing.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: Controlled experiments support the magnetic and smell cues in some species, the evidence for infrasound is still thin

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Map and compass navigation: the mechanism and ontogeny of animal mapsMap cues
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: while there is a large body of literature demonstrating the role of olfactory cues as a navigational map in homing pigeons ... However, there is currently relatively limited evidence in the form of controlled experiments demonstrating that these cues act as the basis of navigational maps in animals.
Supports
Magnetoreception in birdsSection 3.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: These findings clearly show that the magnetic information transmitted by the trigeminal nerve is used for navigation over longer distances.

What this does not establish

The olfactory map is shown mainly in homing pigeons and some other birds, and which odours carry it has proved difficult to establish.

Later work looked for

Europe PMC, 2018 on, map cues in navigation: the 2025 review, now cited, and a 2024 study adding inclination and declination in migrants; the page was corrected for infrasound.

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: and no general account covers the range of animals that do this.

Kind: Open question. Something the page says is not known.
Review: Presented as open. The page says this is unresolved, and the review found that it is.

Supports
Long-distance navigation and magnetoreception in migratory animalsAbstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in animals · Review of the field
The source reads: I contend that any long-distance navigational task consists of three phases and that no single cue or mechanism will enable animals to navigate with pinpoint accuracy over thousands of kilometres.
Supports
Map and compass navigation: the mechanism and ontogeny of animal mapsAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: while extensive investigation into the sensory basis of maps has implicated roles for visual, olfactory and magnetic cues, many details of their mechanism and ontogeny are less well understood

Claim 51 · checked 24 September 2026 · AI-assisted audit

What was read

The Radical-Pair Mechanism of MagnetoreceptionHore and Mouritsen, Annual Review of Biophysics · Abstract from the Crossref record (Annual Review of Biophysics 45: 299–344)Abstract only, 24 September 2026 · Copyright; quoted brieflyThe publisher refuses this environment and the Wayback Machine copy could not be retrieved; only the abstract was read.
Long-distance navigation and magnetoreception in migratory animalsMouritsen, Nature · Abstract on nature.com (Nature 558: 50–59)Abstract only, 24 September 2026 · Copyright; quoted brieflyNot open access and no repository copy found; the body of the review was not read.
Magnetite-based magnetoreceptionJoseph Kirschvink and others, Current Opinion in Neurobiology · Abstract via Europe PMC (PMID 11502393); authors Kirschvink, Walker and DiebelAbstract only, 24 September 2026 · Copyright; quoted brieflyNo open copy; the Caltech repository record carries no file.
Magnetic sensitivity of cryptochrome 4 from a migratory songbirdXu and others, Nature 594, pages 535 to 540 · Accepted manuscript from the Oxford University Research Archive (ORA), read in full, and the published abstract on nature.comRead in full, 24 September 2026 · Copyright; author manuscript; quoted brieflyThe PDF text extraction breaks some words with spaces; excerpts are taken from clean runs. Supplementary information was not read.
Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neuronsTreiber and others, Nature 484, pages 367 to 370 · Abstract on nature.com (Nature 484: 367–370)Abstract only, 24 September 2026 · Copyright; quoted brieflyNot open access; the body of the paper was not read. Its authors’ own later account is in the 2022 review, read in full.
Magnetoreception in birdsRoswitha Wiltschko and Wolfgang Wiltschko, Journal of the Royal Society Interface 16: 20190295 · Europe PMC full text, PMC6769297Read in full, 24 September 2026 · CC BY 4.0A review by the group that first demonstrated the magnetic compass, and which holds that magnetite receptors in the beak exist.
Biophysics of magnetic orientation: strengthening the interface between theory and experimental designKirschvink, Winklhofer and Walker, Journal of the Royal Society Interface 7, supplement 2 · Europe PMC full text, PMC2843999Read in full, 24 September 2026 · CC BY 2.0Written by researchers who work on the magnetite hypothesis. The appendix calculations were not checked.
Magnetoreception: a sense without a receptorNordmann, Hochstoeger and Keays, PLOS Biology 15: e2003234 · Europe PMC full text, PMC5695626Read in full, 24 September 2026 · CC BY 4.0A review from the group whose 2012 study reinterpreted the beak cells.
Myths in magnetosensationNimpf and Keays, iScience 25: 104454 · Europe PMC full text, PMC9167971Read in full, 24 September 2026 · CC BY 4.0A review from the same group as the 2012 study, written to question beliefs on every side.
Do first-time avian migrants know where they are going: the clock-and-compass concept todayChernetsov and Utvenko, Frontiers in Physiology 16: 1562569 · Europe PMC full text, PMC12037376Read in full, 24 September 2026 · CC BY 4.0
Map and compass navigation: the mechanism and ontogeny of animal mapsMorford and others, Animal Behaviour 227: 123272 · Europe PMC full text, PMC7618438 (author manuscript)Read in full, 24 September 2026 · CC BY 4.0