My news feed displayed a semi-popular piece on bird navigation today, a topic that interested me in the 1970s on.
Animals can navigate by starlight. Here’s how we know. (msn.com)
Useful to learn that Emlen's 1966 experimental apparatus: a blotting paper cone, a pudding pan, an ink pad and a wire netting lid were sufficient (eventually) to demonstrate birds' ability to fixate on the star with the least apparent motion - the North Star, by deploying planetarium views.
Another semi-popular account airs the quantum hypothesis which is still controversial.
New Study Fuels Debate About Source of Birds' Magnetic Sense | The Scientist Magazine® (the-scientist.com)
"The cryptochrome theory of magnetoreception is based on quantum mechanics. Cryptochromes are light-sensitive flavoproteins found in the retinas of birds and several other groups of animals, and they’re known to form a pair of radicals—molecules with unpaired electrons—when exposed to light. These electrons have correlated spins, and theoretical and in vitro work indicate that their states can be influenced by magnetic fields, leading to the hypothesis that cryptochrome proteins could provide the basis for animal magnetoreception."
I mention this because of an unexpected finding - unexpected by researchers in animal navigation, that a Faraday Screen around these Emlen pans could dramatically affect magnetic orientation results in certain locations.
Man-Made Electromagnetic Noise Disrupts a Bird’s Compass.pdf (fcc.gov) (National Geographic)
Seven years of double blind experiments with Faraday screens and Emlen pots have narrowed the interfering EM effect on birds' magnetic sense to a band of 4-7kHz.
That is provocative because it contains the second harmonic of the relaxation frequency of proton precession in the geomagnetic field ~ 2kHz