In October 1918, World War I was gradually drawing to a close in the Argonne Forest in northeastern France. Inch by inch, more than one million Allied fighting men slowly wrestled Europe from the occupying Germans, with considerable casualties occurring on both sides. Losses were particularly heavy amongst a battalion of Americans which had pressed too far into enemy territory, leaving 550 soldiers surrounded, outnumbered, and cut off from communications. For days the men valiantly deflected enemy attacks amidst a hail of friendly artillery, but rapidly dwindling forces and supplies soon led to a desperate situation.

Left with no alternative, a member of the US Army Signal Corps named Cher Ami was given the dangerous task of darting past the enemy forces with a message for the Allied commanders. The hastily scribbled note politely requested that headquarters increase the supply of men while decreasing the supply of red-hot shrapnel. As Cher Ami dashed from the forest, enemy gunfire left him with a gunshot wound to the chest and a badly mangled leg, but nonetheless he managed to traverse the twenty-five miles to the command post to deliver his message. As a result, the misplaced battalion was finally rescued.

Cher Ami was awarded France’s Croix de Guerre medal for his heroism, but due to his wounds he did not long survive. When he passed away several months later, his remains were placed in a crate and sent to the Smithsonian Institute in Washington DC, where he was stuffed, mounted, and put on display. Cher Ami, the American war hero, was a homing pigeon.

Though their methods are rather mysterious, homing pigeons such as Cher Ami possess a remarkable ability to relocate their home roost from afar, even across hundreds of miles of unfamiliar territory. For centuries humanity has capitalized on this trait by keeping such pigeons at key locations, then sending a fistful of the feathery messengers along with anyone who might need to send back important information.

Today homing pigeons are mostly the stuff of hobbyists, but until the 1950s they comprised a significant portion of the world’s communication networks. More than 3,000 years ago the ancient Egyptians and Persians took note of pigeons’ tendency to fly back home after being moved, and enterprising pigeon fanciers began cultivating the trait.

A portable pigeon roost from WW1
A portable pigeon roost from WW1

To ensure that only the most skilled homing pigeons were among the breeding stock, the birds were placed in covered baskets and transported to increasingly distant locations; those which returned home had the opportunity to mate, whereas those who lost their way were left to their own devices. Within a few dozen generations, the selectively bred birds had developed uncanny homing abilities, and they were soon pressed into service to relay messages regarding wartime victories and defeats.

Message-carrying homing pigeons remained in service throughout the world for the following three millennia, ferrying information over land and sea at speeds of 30-60 miles per hour. In the 1800s a man named Paul Reuter⁠— later of Reuters Press Agency fame⁠— employed a fleet of pigeons to shuttle stock prices between Belgium and Germany. These plucky birds also provided the world’s first regular air-mail service well before airplanes were invented, linking Auckland, New Zealand with the Great Barrier Island fifty miles away.

During the “War to End All Wars,” homing pigeons were often used alongside radio and telegraph communications. They were valuable as a redundant messaging channel, and prized for their ability to avoid interception and operate during radio silence. Around the same time, a German named Dr Julius Neubronner tinkered with aerial reconnaissance by fitting the birds with small, mechanically-timed panoramic cameras, but results were regrettably inadequate.

In the Second War to End All Wars, homing pigeons were once again drafted into service, this time by a shadowy arm of British intelligence known as Source Columba. Beginning in 1940, the organization airdropped hundreds of crates into occupied France and Holland under the cover of nightfall. Within each crate locals would find a spy kit consisting of 1) a small slip of lightweight paper, 2) a special pencil, 3) detailed instructions, and 4) a single homing pigeon. The instructions encouraged citizen-spies to anonymously jot down any useful tidbits regarding German activities, then stuff the report into the message capsule tied to the pigeon’s leg. Many of the pigeons returned to Britain carrying intelligence which proved immensely valuable in the war effort. In one instance, an enthusiastic informer squeezed thousands of words and fourteen hand-drawn maps onto the tiny message sheet, presumably with the aid of an industrial-strength magnifying glass.

Aerial reconnaissance pigeon
Aerial reconnaissance pigeon

Britain’s Confidential Pigeon Service became such a rich vein of information that it was kept a closely guarded secret for years, but the Axis powers eventually became savvy to the scheme. As part of a clever countermeasure campaign, Nazis dropped their own doppelganger pigeon-crates over France, each designed to appear British. Along with the pigeon these contained a pack of English cigarettes and a request for the names of local resistance leaders, to ensure that the patriots could be “rewarded” for their heroism. Word of the stoolpigeons quickly spread, however, and French forces were advised to “smoke the cigarettes and eat the pigeons.”

In spite of over thirty centuries of close contact with humans, the homing pigeons’ methods are still somewhat mysterious. Biologists have antagonized the birds with countless discombobulating devices, but results have frequently been nebulous. Some have speculated that the pigeons possess extremely sensitive semicircular canals in their inner ear, allowing them to efficiently track the twists and turns of a journey to maintain a constant fix on their home. Tests using rapidly-spinning transport containers, however, seem to refute this theory. Other researchers have suggested that landmarks and/or the position of the sun are used for orientation, but experiments with blinders and fogged pigeon-goggles found that most subjects reached the general proximity of their homes despite severely limited vision. This outcome suggests that visual cues are necessary to find the exact roost location, while some other mechanism guides the bird during the longer segment of the journey. Other exercises included the modification of odors, low-frequency sounds, and lighting conditions in an area, resulting in varying degrees of disruption. Given that no single experiment entirely stripped the homing pigeons of their gifts, it is likely that the birds use a concerted assortment of sensitivities.

A man-made three-axis magnetometer
A man-made three-axis magnetometer

Some of the most intriguing experiments have involved the introduction of strong magnetic fields around pigeons’ home lofts. These fields triggered significant navigational interference with many of the birds, thereby supporting a long-held hypothesis that pigeons possess some sort of natural magnetic compass. The theory was further reinforced by the observation that homing pigeons sometimes become disoriented during the magnetic storms caused by heavy sunspot activity.

In early 2007, a group of German researchers discovered some microscopic structures which may be the mechanism behind these natural compasses: a collection of tiny maghemite and magnetite particles embedded within the nerves of homing pigeons’ beaks. These oblong crystals demonstrated an extreme sensitivity to magnetic fields, appearing to work together to form a three-axis magnetometer. Though biologists are still struggling to grasp the specifics of this mechanism, it seems likely that it allows homing pigeons to sense the relative strength and direction of magnetic north at all times, and thus ascertain their position anywhere on the planet. Considering that most bird species possess an affinity for aerial orientation, many researchers speculate that these natural compasses are a universal avian trait, and that homing pigeons are merely the electromagnetic bloodhounds of the bird world.

Further studies are revealing a plethora of potential uses for these pigeons’ microscopic magnetometers, most notably in areas such as nanotechnology, data storage, and global positioning in general. It is doubtful that a modern misplaced battalion would consider such quaint natural alternatives over man-made GPS receivers and encrypted radios, but these feathery remnants of bygone wars may yet teach us a few things about the technology of global navigation.

Update, April 2018: More recent research suggests that birds’ skills with absolute direction are actually due to a protein called Cry4, a light-sensitive cryptochrome found in the retina. Researchers suspect that quantum interactions between this protein and the Earth’s magnetic field allow birds to “use magnetic compasses any time of day or night.”