Infrasounds and Homing Pigeons

Diagram A shows all releases and random directions pigeons flew; diagrams B,
C, D, and E show different release dates; dashed lines are the correct direction

While we're talking about pigeons, yesterday The Atlantic had an interesting piece about the disappearance of homing pigeons -- who are excellent navigators -- when released from one specific location. One day, though, they flew home with no problem.

After years of not being able to answer the question, the answer has been recently published in The Journal of Experimental Biology: it's infrasounds. Much as human perception is limited to a narrow range of light waves, our hearing is limited to a narrow range of sound. While humans can hear sounds to  ~ 20 hertz, pigeons can hear sounds as low as .05 hertz.

The ocean (or sounds resulting from the ocean) apparently is the dominant source of sounds at that low level even hundreds of miles from the sea. Topography, wind speed and direction, and temperature, however, affect sounds, allowing pigeons to navigate. They also, however, leave dead zones (and surely also places where sound is greatly amplified). The location where the pigeons got lost was normally a dead zone. The one day they didn't get lost was one day where likely high level and not readily apparent atmospheric conditions filled it with sound and allowed the pigeons to find their way.

Pigeon navigation, then, requires not only the ability to hear these sounds but the ability to make a mental map (or remember the sounds they've heard) on one hearing to guide their way back. It's not a common human skill, even for for visual cues.