A proposed explanation for how pigeons detect Earth's magnetic field may not be viable, according to a new study. The theory suggests that pigeons use electrical signals generated in their inner ears to sense direction, but researchers argue that these signals may be too weak and noisy to function effectively as a compass. In a study published in the Journal of the Royal Society Interface, physicist Daniel Kattnig from the University of Exeter found that the proposed mechanism struggles to provide directional information quickly enough due to electrical noise. This challenges the idea that pigeons rely on this specific system to navigate. The theory is based on the idea that turning a conductive loop in a magnetic field generates a voltage, similar to how a generator works. In pigeons, the inner ear’s semicircular canals—normally used to detect head movement—contain a salty fluid that conducts electricity. Earlier research, including a 2019 study in Current Biology, showed that electrical signals could be generated in lab models of these canals, and that certain molecular components in pigeon inner ear tissue are involved in sensing these signals. Later research by Gregory Nordmann and colleagues, published in Science, supported this by showing that magnetic stimulation could activate brain regions linked to balance, even in darkness. They also identified specialized sensory cells that express genes for voltage-sensitive channels, suggesting a possible link between magnetic sensing and balance. For his study, Kattnig created a model of the inner ear canal as a small ring of conductive fluid, interrupted by a gelatinous barrier called the cupula. He initially assumed the barrier acted as a perfect insulator, which gave the model ideal conditions. However, even under these favorable conditions, the predicted voltage was extremely small—about 12 billionths of a volt. While such a small voltage might still be usable in some contexts, the real issue lies in the random movement of electrical charges, which creates noise that can overwhelm the signal. Kattnig found that even with filtering techniques to reduce noise, the system still couldn’t provide directional information quickly enough. The pigeon's head constantly moves, and the compass system would need to associate changes in the signal with specific directions. Using information theory, Kattnig estimated how fast the noisy system could provide directional data. His idealized model produced only about 0.15 bits of information per second, far below the 560 bits per second needed to distinguish directions as fine as 5 degrees apart. Allowing some electrical leakage in the model further weakened the signal. Even more sensitive cells or additional brain processing couldn’t recover the missing information quickly enough. This leaves researchers puzzled: while biological observations suggest a magnetic response tied to the balance system, this specific mechanism doesn’t seem to explain how pigeons navigate effectively. Scientists now need to explore alternative mechanisms or physical processes that could account for both the observed brain activity and the need for precise directional information.