From Newsgroup: talk.origins
https://www.science.org/content/article/mind-blowing-iron-rich-immune-cells-help-homing-pigeons-navigate
It isn't exactly their guts, but some researchers have produced evidence
that macrophage in the liver are associated with a pigeon's ability to navigate using the earth's magnetic field. When macrophage scavenge
worn out red blood cells they sequester the iron as ferritin. In
pigeons the iron rich macrophage congregate in the liver. They treated pigeons with a drug that reduced ferritin levels in macrophage and the
pigeons could not find their way home on cloudy days when they could not
use the sun to navigate.
Ron Okimoto
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