Experiments : Seven Experiments : Homing Pigeons

Homing Pigeons

"Numerous experiments on homing have already been carried out with pigeons. Nevertheless, after nearly a century of dedicated but frustrating research, no one knows how pigeons home, and all attempts to explain their navigational ability in terms of known senses and physical forces have so far proved unsuccessful. Researchers in this field readily admit the problem. 'The amazing flexibility of homing and migrating birds has been a puzzle for years. Remove cue after cue, and yet animals still retain some backup strategy for establishing flight direction.' 'The problem of navigation remains essentially unsolved.'

The inertial navigation hypothesis [that pigeons 'register the twists and turns of the outward journey'] can...be ruled out, and is no longer seriously entertained by researchers in the field.

The leader of the Göttingen team, Klaus Schmidt-Koenig, summarized as follows the conclusions from a long series of experiments on pigeons with frosted-glass lenses, including the detailed tracking of homing birds by radio:

For the navigational part of the homing flight, i.e., determining which direction is the home direction, visual cues turned out not to be essential. This navigational system is largely non-visual and guides the pigeon with amazing accuracy to the vicinity of the loft. The birds also seem to know when they are home and when they have missed the loft and the distance is again increasing.

On sunny days, the 'sun-compass' of pigeons can play a part in their general sense of direction when they are released. But it cannot explain their ability to find their way home.

Another unusual sensory ability sometimes invoked as a possible explanation for pigeon homing is infrasound. Pigeons are known from laboratory experiments to be unusually sensitive to low-frequency sounds. But this does not prove that they can hear their homes from hundreds of miles away, or even from a few miles. The idea that they might home by means of infrasound is not even a hypothesis but just a vague and implausible suggestion. There is no evidence whatever to support it.

The conclusion from [research on smell] is that in some circumstances, especially in Italy, the sense of smell plays a part in the orientation of pigeons, but it cannot by itself explain how pigeons find their homes.

Pigeons' magnetic sensitivity has also been tested in laboratory experiments. Most of the published results have failed to show any significant effects of magnetic fields, and in addition many other negative studies have remained unpublished. One of the leading investigators in the field, Charles Walcott, has come to the conclusion that: 'Given the weight of all this negative evidence, coupled with the circumstantial nature of the positive evidence, it becomes very difficult to believe that the pigeon makes use of magnetic cues for its "map"'.

The magnetic hypothesis was the last seemingly viable attempt to find a mechanism for homing. Many have clung to it with the tenacity of drowning men clutching straws. Now this hypothesis too has sunk.

Among professional researchers, the currently conventional view is that pigeon homing depends on a complex series of 'backup systems'; or that it is 'multifactorial', involving subtle combinations of mechanisms, such as a sun-compass, smell, and magnetism; or that pigeons use a single (unspecified) type of information, but 'scan it with several sensory systems'. But these scientific-sounding phrases merely disguise a profound ignorance. The orthodox paradigm has broken down.

A direct connection between pigeons and their homes

I propose that the sense of direction of homing pigeons depends on something rather like an invisible elastic band connecting them to their home, and drawing them back toward it. When they are taken away, this band is stretched. If on their return flight they overshoot their home, as some of the pigeons flying with frosted-glass contact lenses did, this connection serves to pull them back again.

I do not know how this interconnection might work. It might be related to the nonlocal connections implied by modern quantum physics, first pointed out in the Einstein-Podolsky-Rosen paradox. Einstein regarded the nonlocal implications of quantum theory as absurd; he rejected the notion of an instantaneous linkage between two separated quantum systems that had once been together. But, in the form of Bell's Theorem, quantum nonlocality was tested experimentally in 1982 by Alain Aspect, and Einstein turned out to be wrong.

Assuming one rules out faster-than-light signalling, [this result] implies that once two particles have interacted with one another they remain linked in some way, effectively parts of the same indivisible system. This property of 'nonlocality' has sweeping implications. We can think of the Universe as a vast network of interacting particles, and each linkage binds the participating particles into a single quantum system. Although in practice the complexity of the cosmos is too great for us to notice this subtle connectivity except in special experiments like those devised by Aspect, nevertheless there is a strong holistic flavour to the quantum description of the Universe.

Perhaps the link between the pigeon and its home rests upon such nonlocal quantum phenomena. Perhaps it does not, but rather depends on some other kind of field or interconnection not yet recognized by physics. I simply leave this question open.

Another way of formulating this idea of a connection between the pigeon and its home is throughthe concepts of modern dynamics. In mathematical models of dynamical systems, systems move within a field-space toward attractors. In these terms a homing pigeon could be modeled as a body moving within a vector-field toward the attractor, representing its home or goal.

For the sake of simplicity, I shall take the crudest formulation of this idea, the metaphor of an invisible elastic band between the pigeon and its home. This connection gives pigeons a sense of direction, enabling them to find their way home even when they cannnot remember the outward journey, nor see landmarks, nor use a sun-compass, nor smell, nor detect the earth's magnetic field. It enables them to overcome the fiendish confusions imposed on them by experimenters, including releasing them in heavily overcast weather or at night, shifting their time sense, blocking their nostrils, confusing them with odors, fixing magnets to them, rotating and anaesthetizing them, blinding them with frosted-glass contact lenses, and cutting their nerves.

This band is stretched when the pigeons are taken away from their home. But it should also be stretched under the converse condition: when the home is taken away from the pigeons. This is the basis of the experiment I propose. Instead of the pigeons being taken away from their loft, the loft is taken away from the pigeons. Can the pigeons find their missing home?

An experiment with mobile lofts

The experiment I propose involves a mobile pigeon loft, mounted on the back of an old farm trailer. The pigeons in the loft are first trained to home in the normal way, just like ordinary homing birds. Then they are trained to home to the mobile loft. The basic procedure is to take some of the pigeons out of the loft and keep them in a pigeon-carrying basket. The loft is then towed away, still containing some of the pigeons, including the mates and offspring of those removed. Then the birds in the basket are released at the place where the loft used to be. They can see immediately that their home has gone. Can they find it?

If pigeons can find the mobile loft repeatedly, rapidly, over long distances, in arbitary directions and when the loft is moved downwind (eliminating any possibility of smelling its direction), this would show that there is a direct connection between the pigeons and their home. On the other hand, ifthe pigeons cannot find the mobile loft, even with the other pigeons inside it, the outcome would unfortunately be inconclusive. It could mean that there is not invisible connection between the pigeons and their home. Or it could mean that there is a connection to the home, but moving the loft alone is not enough. More of the home environment might need to be transported, for example by mounting the loft on a ship.

Of relevance in this connection is a report I have received from a Dutch correspondent, Mr. Egbert Gieskes, of a mobile loft on the river Rhine:

A Dutch skipper, owner of a riverboat, brought goods from sea vessels in Rotterdam with his boat to Germany or Switzerland. His pigeons were flying every day around his ship during his trip up or down the river Rhine. One day he offered a friend in Rotterdam a basket with three pigeons and said: 'Let them free after five days, look at what they do and write down the time.' Half a day later the pigeons came to their loft in Basel, between a lot of other ships.

This story is not quite as surprising as the use of lofts on ships at sea by the Italian Navy [described earlier in the chapter], since the pigeons were familiar with the Rhine and could simply have flown upriver until they found their boat. But it does suggest a potentially simple experiment which could be done with the help of this or any other riverboat skipper who keeps pigeons on the Rhine. Instead of releasing the birds at Rotterdam, at the mouth of the Rhine, where there is only one direction in which they can fly along the river, they could be released roughly half way along the Rhine, say at Koblenz, in Germany. Neither the pigeons nor the person releasing them would know which way the boat was going, to Rotterdam or Basel. If in a series of experiments the pigeons repeatedly went in the right direction and found the loft straightaway, rather than flying up- or downriver at random, this would indicate the existence of an invisible connection between the birds and the loft.

Unless one happens to know a friendly ship's captain, it is simpler to start this line of research with ordinary mobile lofts on land. And the first step is to train the birds to home to the mobile lofts over short distances. Pigeons, like people, do not notmally expect their home to move. The first time it happens they are very confused, just as most people would be if they went home and found a gap where their house used to be. Even if they could plainly see the house some distance down the road, they would be unlikely to walk straight in as if nothing had happened. But if it kept doing this, they would just get used to it. And so do pigeons.

How to begin

I would strongly advice anyone taking up this experiment to find an experienced pigeon fancier to advise and help them, unless they are already experienced in keeping pigeons. Successful work with pigeons depends on the basic skills of handling, training, and caring for the birds, and on forming a good relationship with them.

In the Practical Details section at the end of the book, I list the addresses of pigeon magazines and organizations where information can be found about local groups of fanciers, loft kits, commercially available pigeon feed, and other practical matters. Young birds can be purchased from local fanciers, or they may well be given. In my experience, most pigeon fanciers are well aware of the unexplained nature of the homing instinct, take a friendly interest in practical research on the subject, and are in any case very helpful to people establishing new lofts.

Once the loft is established, the birds well settled and used to homing in the normal way, they should then be trained to find the mobile loft, starting with short moves. When the pigeons are used to homing to the mobile loft, it can be moved further and further. The further it is moved, the more interesting the results will be.

It is, of course, essential to keep a detailed written record of the setting up of the loft and of the training flights, and in the experiments to take careful notes of the weather conditions, wind direction, exact time of release of the birds, and the time at which they first appear near the mobile loft.

If the pigeons can indeed find their home even after it has been moved far away, say 50 miles, the time they take will be crucial. If they take weeks to find it, this could be the result of random search, and would not therefore provide evidence for a direct connection between the pigeons and their home. But if they reach the loft within an hour or two, they would have had to fly there more or less direct. And if this effect were repeatable at a variety of locations, under conditions when the loft was not upwind, then it would prove the existence of a direct connection between the pigeons and their loft.

Many further questions could be asked. For example: is the connection more to the other pigeons or to the loft itself? To investigate this, the other pigeons could be removed from the loft and kept in one distant place, while the loft itself is taken somewhere else. Do the test pigeons head for the other members of the flock, or for the empty loft? A new field of research would open up.

Pets who find their owners

If pigeons can indeed find their home and their companions after the loft has been moved far away, then a series of strange but persistent stories about pets will be seen in a new light. There are many accounts of homing pets, as discussed above; but there are also many stories about pets left at home finding [caretakers] that have moved. Such stories have been told for centuries. For example, in the sixteenth century, a greyhound named Cesar was said to have followed his master from Switzerland to Paris, setting off three days after his master had left by coach. The dog somehow found his master at the court of King Henri III. In an even more heroic example of canine devotion, we are told that during the First World War a British dog named Prince found his way across the English Channel to his master's side at the battlefront in France.

Most modern cases come to light through reports in local newspapers. For example, when a family was leaving California for a new home in Oklahoma, their Persian cat, Sugar, jumped out ofthe car, stayed a few days with neighbors, and then disappeared. It turned up a year later at the family's new home in Oklahoma, having traveled well over 1000 miles through unfamiliar territory. Tony, a mongrel dog belonging to the Doolen family from Aurora, Illinois, was left behind when the family moved more than 200 miles north-east to East Lansing, Michigan, around the southern tip of Lake Michigan:

When the Doolens left Aurora they gave Tony away, but six weeks later he appeared in Lansing, excitedly approached Mr. Doolen on the street, and was recognized. Identity was established by the collar which Mr. Doolen had bought in Aurora and had cut down to Tony's size. A right-angled notch had been cut for an extra hole. Both the Doolen family (of four) and the Aurora family who gave them Tony as a pup recognized the dog, and Tony's behavior confirmed his identity.

There is even a case of a pet pigeon finding its owner, the twelve-year-old son of the county sheriff in Summersville, West Virginia. The racing pigeon, number 167, had stopped in his backyard; the boy fed and cared for it, and it became his pet.

Sometime later the boy was taken to Myers Memorial Hospital at Philippi, 105 miles away (70 miles by air) for an operation, and the pet pigeon was left behind in Summersville. One dark, snowy night about a week later, the boy heard a fluttering at the window of his hospital room. Calling the nurse, he asked her to raise the window because their was a pigeon outside, and just to humor the lad, she did so. The pigeon came in. The boy recognized his pet bird and asked her to look for the number 167 on its leg, and when she did she found the number as stated.

Skeptics inevitably dismiss them as anecdotal, just as they used to dismiss stories about the homing of pets. Experimental research has now confirmed the reality of homing behavior in many animal species, even though it remains unexplained. Likewise, if it can be demonstrated experimentally that pigeons can find homes that have moved, stories about pets finding their [caretakers] will have to be taken more seriously.

The biological context for this apparent ability may be the way in which social animals find other members of their group when separated from them. Some observations on wolves by the naturalist William Long seem relevant here:

In the winter time, when timber wolves commonly run in small packs, a solitary or separated wolf always seems to know where [its] mates are hunting or idly roving or resting in their day bed. The pack is made up of [its] family relatives, younger or older, all mothered by the same [wolf]; and by some bond or attraction or silent communication [it] can go straight to them at any hour of the day or night, though [it] may not have seen them for a week, and they have wandered over countless miles of wilderness in the interim.

Through long periods of observation and tracking, Long came to the conclusion that this ability could not be explained simply in terms of following habitual paths, or by following scent trails, or by hearing howling or other sounds. For instance, he once found a wounded wolf that had separated from the pack, and lay recovering in a sheltered den for several days while the others ranged widely. Long picked up the trail of the pack while they were hunting, tracked them through the snow, and was close by when they killed a deer.

They followed, killed and ate in silence, as wolves commonly do, their howling being a thing apart from their hunting. The wounded wolf was then far away, with miles of densely wooded hills and valleys between [her] and [her] pack.

When I returned to the deer, to read how the wolves had surprised and killed their game, I noticed the fresh trail of a solitary wolf coming in at right angles to the trail of the hunting pack. It was the limper again. . . I picked up [her] incoming trail and ran it clear back to the den, from which [she] had come as straight as if [she] knew exactly where [she] was heading. [Her] trail was from eastward; what little air was stirring came from the south; so that it was impossible for [her] nose to guide [her] to the meat even if [she] had been within smelling distance, as [she] certainly was not. The record in the snow was as plain as any other print, and from it one might reasonably conclude that either the wolves can send forth a silent food call, or else that a solitary wolf may be so in touch with [her] pack mates that [she] knows not only where they are but also, in a general way, what they are doing.

Such connections may be a normal feature of animal societies, even though we have hardly begun to understand how they work. In the following chapter I consider a very different example, termite colonies, in which the individual insects also seem to know where the others are and what they are doing. As in the case of wolves, and of pets that know when their owners are coming home, and of pets that find their owners, and of pigeons that find their lofts, and of homing behavior in general, and of migration, appropriate explanations may lie beyond the current limits of science."