A homing pigeon released hundreds of miles from home can often find its way back with remarkable accuracy.

People have marveled at this ability for centuries. Yet exactly how pigeons navigate remains one of biology's most enduring puzzles.

Many scientists suspect that birds can sense Earth's magnetic field, giving them a kind of built-in compass. But where that compass is located, and how it works, has been debated for decades.

Scientists may have identified specialized liver cells that help pigeons detect Earth's magnetic field.

The idea is surprising because most people would expect a navigation system to be located in the eyes, ears, or brain.

The discovery does not fully explain how pigeons find their way home. Birds likely combine several sources of information, including the Sun, stars, landmarks, odors, and Earth's magnetic field.

Even so, the finding offers an intriguing possibility.

Part of the navigation system that guides a pigeon across unfamiliar landscapes may be hidden in an organ few people would ever suspect.