March 28, 2008

Carrier Pigeons

Stupid Question ™
Feb. 21, 2002
By John Ruch
© 2002

Q: How do carrier pigeons work? Are they still used today?
—Ben Hauck

A: First things first: we’re really talking about homing pigeons—pigeons bred to be especially good at finding their way home. Carrier pigeons are homing pigeons carrying messages. Racing pigeons are homing pigeons bred and trained to fly home as fast as possible.

All pigeons have some degree of homing ability. Humans have been breeding homing pigeons for millennia.

Until radio, the carrier pigeons was the fastest means of long-distance communication. It was also simple: get the pigeon comfortable in its loft. You an ten take it great distances away and release it, and it will return home. Vast pigeon networks were built this way.

The famous Reuters news service began in 1851 as a carrier-pigeon network. The US military used carrier pigeons up through the Korean War; Iraq used them in the Gulf War.

Today, carrier pigeons are used regularly only in remote areas of countries such as India. In the industrialized world, their use is whimsical or idiosyncratic: a 1998 attempt to smuggle diamonds from a South African mine by pigeon, or an Internet connection achieved last May by carrier pigeons.

The primary use for homing pigeons today is racing. The strong, fast racing breeds were started in Belgium around 1810. Racing pigeons today can fly 60 mph and find their way home from up to 1,000 miles away (though some do get lost).

The homing ability is a mystery, especially since it’s employed so quickly and with no apparent effort.

In experiments in which pigeons were fitted with frosted goggles that admitted only diffuse light and released 100 miles from home, most were able to navigate to within a quarter-mile of their loft. This suggests that regular vision is important in finding the exact loft, but that something else is involved in the long-distance journey.

That something is probably several abilities used in concert. They almost certainly use the Sun for general orientation, and possibly can somehow calculate their position based on its position.

Pigeons can hear extremely low-frequency sounds (down to 0.05 hertz) and can see ultraviolet light. Evidence suggests they are also sensitive to Doppler and polarization shifts in such sound and light, meaning they could use them to orient themselves.

Most remarkably, pigeons almost certainly have an internal magnetic compass. Experiments show that they have trouble navigating if an electromagnet is placed on their heads. There is also correlation between sunspot activity, which can cause magnetic storms on Earth, and mass mis-navigation. (Most pigeon-racers monitor sunspot activity.)

Furthmore, the compass has apparently been found. It’s a tiny bit of tissue in the head that contains about 10 million oblong crystals of magnetite—a magnetic iron oxide that makes a perfect compass needle. The shape and tiny size of these crystals probably makes them an extremely sensitive compass, which the pigeon “reads” by sensing pressure changes as the tissue expands in various directions based on orientation to the Earth’s magnetic field.

No comments: