Fanciers have given great attention to the eye as a means of choosing racers and producers. This in general has been done to standards of eye-sign qualities arranged arbitrary by a few fanciers in Belgium and in Britain who profess to have given many years of patient analysis of thousands of racing pigeons to arrive at their stated conclusions.

In short, they claim a pigeon with little eye-sign or lack of depth in the coloration would be a poor producer and almost certainly a moderate racer.

My curiosity on this subject was roused when in Belgium in 194415 and in the intervening years I have done a little practical work on my own account. Of greater value, I have lost few opportunities to enquire of leading British and Belgian fanciers whom I felt sure would have a considered opinion. I trust a few of the more illustrious will not object to my using their names to establish my bona-fides-Messieurs Delbar, Fabry, Huyskens Van Riel on the Continent, and Messrs. T. A. Warrington, Hugh Cropper, T. Dawson, G. McKelvie, Drs. Anderson and Rigg in Britain. All agree on the value of a good eye-an eye that is bright, intelligent and of a rich colouring. But what colouring, who cares?

In addition I have put the question to an eminent scientist, whose investigations into bird migration and their ability to find a way even over thousands of miles has occupied his attention for years, and to ophthalmologists besides. These men of science find nothing to suggest any scientific background to the claims made by " Eye-sign adherents.

Below is some correspondence on the matter, the letter from Dr. Hubbard having already appeared in The Racing Pigeon in December, 1954, and my article " Eye-Sign and Homing," which has also appeared elsewhere.

If we racing pigeon fanciers accept the dictum " a good pigeon cannot have a bad eye " we may look elsewhere for more positive physical indications to racing value. An assessment in the hand is worthwhile if we are skilled enough to make a reasonably true one, bearing in mind that on a bad day the basket loses both good and bad.

Eye-sign means something. It means on a race day a particular pigeon, equal in all respects except in the eye to that of its competitors, will, wind and drag being of small account, be first home if it has a superior eye-sign. To we racing pigeon fanciers, if it does not mean that, it means nothing.

In the last ten years a lot of research has gone into bird navigation, not by pigeon fanciers, but by scientists with no object in view but to find out how birds find their way over many miles of strange sea and land.

Every conceivable test, it would seem, has been made with the five senses to find the answer. Touch, smell, hearing and taste have been disposed of as giving no, or little help in finding the answer. Association with smells, and disassociation, by peculiar loft odours in the one case, and by blocking up the nasal passage in the other, has neither added to nor detracted from racing pigeons powers to find their loft in numbers or in speed.

Dr. G. V. T. Matthews, lately of the Department of Zoology, University of Cambridge, with his book, Bird Navigation gives a concise summary of the latest findings. Therein are listed dozens of species of birds he himself has used for experiments. Manx Shearwaters by the hundred he has taken at different times distances of 65 to 3,050 miles and had them successfully home, from the longest journey across the Atlantic in 12 days; gulls 1300 miles, swallows 1150 miles and starlings too.

He concludes that only through sight or an undefined sense can a solution be found. A wide variety of experiments have rejected that birds are capable of detecting the magnetic poles and maintaining a bearing therefrom. Pigeons orientating their flight in the training direction have done so undisturbed by powerful magnets swinging below the head or attached to the wings.

The idea of the sun acting as a point of reference, surprisingly, has only slowly aroused interest. It has come with a great number of experiments that show conclusively (a fact long well known to racing pigeon fanciers) with the sky heavily overcast there is only a confused sense of orientation, whereas when the cloud is dispersed birds become strongly orientated.

It is probable, speaking of birds generally, that night travellers take their last bearings from the setting suntheir ready drift in the dark when encountering side winds over the sea fits in with this belief.

Theories calling for radiations of an unspecified nature from the home area frequently crop up. Then there is the suggestion that some extra sensory means of orientation is the basis of homing, but it is difficult to imagine if their existence were proven, how telepathy, or clairvoyance, could help in this way. Their independence of ordinary considerations of time and space has been strongly emphasised by their advocates so they could hardly be of use for two dimensional orientation.

Neither would a succession of visual landmarks be available to pigeons flying hundreds of miles over strange ground at a height not exceeding 200 feet and a horizon not 20 miles, though it is probable the final pin-pointing of the loft is brought about in this way.

Or again, the retracement theory whereby a pigeon remembers the outward journey with all its twists and turns in the enclosure of its container and faithfully follows the path back.

Observation shows that pigeons sleep en route and it would then have to be presumed the recording process went on during unconsciousness. Transportation has been made with birds under anaesthetic and in no case were homing results poorer in comparable circumstances than with untreated birds.

Dr. Matthews carried out a number of tests with racing pigeons, following up this idea of birds remembering the journey to the point of release. He used a large light-proof drum with pigeons in it, turning it throughout the journey, sometimes slower, sometimes faster, but the performances of the rotated birds, liberated apart, were just as good as untreated birds.

We may conclude that recording of the travel route in the brain of the pigeon during the journey to the release point could not act as a basis for discovering the route home.

The effect on homing of the earth's magnetic field, or radar, or wireless and television waves, can almost certainly be discounted by the tests made with magnets attached to the wings of greater intensity, due to their nearness to the bird, than any of those possible influences.

In one experiment electric currents were passed through the heads of pigeons before release, but again without apparent effect on their ability to home.

In 1951 Matthews put forward the suggestion of sun navigation as worthy of the most serious consideration as the main feature in homing ability based briefly on the following evidence.

The ability to home in sunny weather deteriorates markedly in conditions of heavy cloud and that those individual pigeons which gave good orientation in sunny conditions scattered at random with an overcast sky. Speed and proportion of returns fell from 71 % in sunny conditions to 43% in heavy cloud.

At this point it may be noted that it is most unusual for the general position of the sun not to be made out in Spring and Summer in any but the heaviest overcast conditions so that for homing on a constant compass bearing to break down entirely from this point of view is very rare indeed.

Pigeons can be said not to fly at night; they are purely day birds; after dark experiments are unnatural to them. True, after intensive training with additional guides from lamps over the loft, pigeons have been made to fly in the dark over short distances, and this is explicable on a basis of developing an intimate local knowledge.

On the other hand, the Manx Shearwater, of the gull family and roughly the size of a pigeon, while habitually flying and feeding at sea in the day only, flies in the neighbourhood of the nesting area after dark, probably to avoid the attacks of the large gulls that molest them on land when they attempt to seek their nest in the light. This does not imply an ability to home after dark, since the birds assemble near at hand before dusk and find, probably, their way over short distances by means of familiar objects; but it does mean they are, unlike the pigeon, willing to fly at night and so are available for experiment to check whether or not they show an ability to find their way at night if released in an unknown area after dark. The Shearwater, as has been said already, is one of the world's finest homers. Three thousand miles in 12 days beats anything the racing pigeon has ever attempted.

One night 20 Shearwaters were released singly 60 miles inland-mainly to ensure they would not rest, if possible, since the bird normally comes only to land at its nest-less than two hours' flying time away, in good weather, so giving a very generous allowance of time to return home before the morning light if they were able to orientate themselves on release.

Not a single bird of the twenty got back that night. Eleven were at the nest next night, showing the urge to return was present and only the ability to do so was lacking. Six of the birds then were released in the dark off the home island and five were back at the nest the same night, pointing to an intimate local knowledge.

This evidence, together with that of clear and overcast sky, strongly suggests dependence on a form of sun navigation. It has been suggested that overcast sky might cause an emotional upset, thereby disarranging the sense of orientation, but it is difficult to believe that birds so long used to the British climate would be much disconcerted in this way.

That pigeons do pick up landmarks Dr. Matthews has shown, for after six previous releases from one place, overcast conditions have no effect on them and they found the line home straight away. Thereby, too, the theory of emotional upset in heavy weather seems to have little value.

Experiments to find the effect of the earth's rotation and those of magnetism on pigeons homing have been tried and rejected; to-day no possible fresh lines for research are known. It would be a bold biologist who claimed that we know all there is in living tissue, but it is unthinkable that a physical characteristic of the earth, prominent enough to be detected by birds to establish their position and set out in a certain preselected direction, should have been overlooked.

What of the suggestion that birds have an unknown acute natural sense of latitude and longitude (grid) but prefer to see the sun in addition to strengthen their decisions?

In that case, overcast conditions should no more than cause a momentary hesitation and a slight reduction in the speed of return. In a test 25 pigeons of proved ability to home well from 110 miles were released 25 miles from a point twice visited before at fairly long intervals. Heavy overcast conditions prevailed and the landmarks were not sufficiently well known to help in finding a direction for home.

The gloom persisted for days, but the unknown grid should have been sufficient to ensure the birds homing in reasonable time. Instead, two were back day of release, two next day, six on the third, two on the fourth, one the sixth and one the eighth day. Six more turned up after the tenth day when the weather improved. There is no doubt the birds were completely disorientated and not just lacking in a compass.

Dr. Matthews then concentrated on the remaining possibility of birds actually getting the co-ordinates of the release point, in relation to those at home, by information derived from the sun.

A strong point in favour of bearings from the sun is its reliance on the one sense organ we know to be exceptionally well developed in birds-the eye.

Menner, another investigator, suggested that the pecten, primarily a nutritive organ, plays a vital part in the dioptic system by virtue of the foliated shadow it casts on part of the retina. He concluded that it enhanced the ability of movement detection. This was based on the use of models of the apparatus and by showing that the foliations were particularly well developed in those species dependent on the capture of moving prey.

The exact reason for the phenomenon is not understood, but the shadows probably increase the contrast as the observed object passes across the field of vision.

We all know that the behaviour of a pigeon at release is to circle before departing, giving the impression of " getting their bearings. " Here again Dr. Matthews has carried out many experiments to show that in cloudy conditions, watching through binoculars until out-of-sight, pigeons released singly on an average take four minutes to clear and went off in all directions, while in good conditions the
time was nearer three minutes with good homeward orientation.

To summarise: there appears good evidence for an association of eye and sun and the existence of some form of " watch " mechanism in a bird's brain keeping good time despite experiments lasting over several days designed to disorganise the rhythm of its working, yet the nature of it remains quite obscure.

Observation in migration has shown that birds have a very clear appreciation of time, their comings and goings being most regular, particularly with those birds having far to travel, indicating a gearing to the sun in its seasonal lengthening and lessening arc. Thus it seems the sun-arc may provide the purpose, cause and guide of migration.

Scientists are agreed that no theory of bird navigation remains to be investigated except that involving the sun, leading to the conclusion that, while we may not have the complete solution to the homing of racing, pigeons, we have narrowed the field for investigation to that of the sun on
the one hand and the eye as the window of the pigeon's brain on the other. At the time of writing Mr. Pennycuick, of Cambridge University, is actually making experiments on these lines.

The working of a pigeon's brain is still almost entirely obscure, but we can recognise the shortcomings of our birds when the limits of fatigue are not involved as in the 1955 Pau race. One, often its inability to take an exact bearing on a clear day or a directional one on a dull day. Two, its lack of superlative eyesight to detect what small sun indication there might be. Three, that with superlative eyesight comes greater confidence to perform its task, we might see in the eye, not the be all and end all of good homing, but a big factor contributing to the better bird.
If we accept something like that, then comes the question, "What makes the better eye?" Is it in eye-sign, in the accepted sense we pigeon fanciers understand it? A lot of tarradiddle may be talked about the eye (spare my blushes) but we should keep the eye in the forefront of our deliberations and not dismiss the subject as chatter for the cranks.

So far as I am aware, nothing has been written in this country by a competent authority, one professionally skilled in optics, on racing pigeon eye-sign, either in support or condemnation.

Several earnest pigeon fanciers have given their opinions based on little or much superficial research, generally based on the process of examination of champions. Eye colourings and iris shadows have been tabulated, purporting that eyes of certain colours and shadows hallmark the quality of racing pigeons.

This is far removed from an accepted specialist in the eye, and one who has given time to homing research in relation to the eye, coming along and giving an opinion in the superiority of eyes of certain colourings and shadows for reasons established scientifically.