Evidence for a plausible mechanism for bird navigation

[jillery]

It's common knowledge that migratory birds have a remarkable talent
for finding their way over vast distances. What is still uncertain is
how they do it. One plausible mechanism is a molecule that responds
to the Earth's magnetic field, which hypothetically could provide them
with the ability to sense both longitude and latitude.

Cryptochromes have been suggested as plausible molecules. Blue light
causes the protein to produce radical pairs, whose electrons' spin are
quantum-entangled to have different orientations, but can be altered
by external magnetic fields. The different orientations cause
different chemical reactions.

<https://royalsocietypublishing.org/doi/10.1098/rsif.2018.0058>

<https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0001106>

However, the Earth's magnetic field, while very large, is also very
weak, about ten thousand times weaker at Earth's surface than a
typical refrigerator magnet. Until recently, there was no evidence
cryptochromes responded to it.

A paper published last June describes an experiment where the authors
modified candidate cryptochromes to fluoresce in vitro when they
produced particular molecules under an external magnetic field of a
strength similar to Earth's magnetic field:

<https://pubmed.ncbi.nlm.nih.gov/24689535/>



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