A new study says homing pigeon livers act like compasses. Other experts aren't so sure

Homing pigeons navigate using Earth’s magnetic field, but prior explanations have not been confirmed. A new hypothesis proposes that pigeon livers function like compasses. The hypothesis identifies magnetic immune cells in the liver packed with a specific form of iron. Experiments show that removing these cells interferes with the birds’ ability to navigate. The mechanism for how geographic information is extracted from these cells has not been established. Researchers remain optimistic that the process will be clarified. Other experts question whether the findings withstand scrutiny and note concerns about how liver macrophages handle iron from dead red blood cells.

"The study, published today in Science, finds that homing pigeon livers are packed with magnetic immune cells containing a specific form of iron and that removing these cells messes with the birds' navigation. The study authors haven't established how the pigeons might glean geographic information from these cells, but they're optimistic that they will figure this out soon."

"What we think we found here really fits all the evidence that's out there, says Martin Wikelski, a researcher at the Max Planck Institute of Animal Behavior in Radolfzell, Germany, and a co-senior author of the study. He thinks the new hypothesis could be possibly happening from bees to mammals and bats to all kinds of birds, and so on."

"Biologists have been unable to confirm the myriad previous theories for the pigeons' navigational abilitiesfrom magnetite in their beaks to quantum entanglement in their eyesand some experts are already saying the new theory doesn't stand up to scrutiny, either. I am not convinced, says Joe Kirschvink, a geobiologist at the California Institute of Technology, who has studied the relationship between Earth's magnetic field and animals for decades and was not involved in the new study."

"The new theory rests on macrophages in homing pigeons' liversthese immune cells are the body's garbage disposal. When a red blood cell dies, the carcassand the iron it containsdoesn't just lay around, or it would inflame the surroundin"

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