Chapter II: Part 2

Our mountain ash trees have told us several facts about the sapsucker:--

That he did not come to eat insects.

That he did come to drink sap, and that he probably ate the inner bark also.

That he drank the sap because he liked it, not for some secondary object, as insects.

That he could detect difference in the quality or quantity of the sap, which caused him to prefer a particular tree.

That this difference apparently was in the taste of the sap, and that the effects of a day's drinking of mountain ash sap seemed to indicate some intoxicant or narcotic quality in the sap of that particular tree.

That the effect of his work upon the tree was apparently injurious, as it is the only cause assigned of a healthy tree's dying before a less healthy one of the same age and species, subject all its life to the same conditions.

So much we have learned about this sapsucker's habits, and now we should like to know why his work is harmful, and why that of the other woodpeckers is not. It is not because he drinks the sap. All the sap he could eat or waste would not harm the tree, if allowed to run out of a few holes. Think how many gallons the sugar-makers drain out of a single tree without killing the tree. But the sugar-maker takes the sap in the spring, when the crude sap is mounting up in the tree, while the sapsucker does not begin his work till midsummer or autumn, when the tree is sending down its elaborated sap to feed the trunk and make it grow. This accounts for the woodpecker's digging his pits _above_ the lines of the holes already in the tree. The loss of this elaborated sap is a greater injury than the waste of a far larger quantity of crude sap, so that on the season of the year when the sapsucker digs his holes depends in large measure the amount of damage he does. The injury that he does to the wood itself is trivial. He is not a wood_pecker_ except at time of nesting, and most woodpeckers prefer to build in a dead or dying branch, where their work does no hurt. But we know very well that a tree may be a wreck, riven from top to bottom by lightning, split open to the heart by the tempest, entirely hollow the whole length of its trunk, and yet may flourish and bear fruit. The tree lives in its outer layers. It may be crippled in almost any way, if the bark is left uninjured; but if an inch of bark is cut out entirely around the tree, it will die, for the sap can no longer run up and down to nourish it.

This is the sapsucker's crime: he girdles the tree,--not at his first coming, nor yet at his second, not with one row of holes, nor yet with two; but finally, after years perhaps, when row after row of punctures, each checking a little the flow of sap, have overlapped and offset each other and narrowed the channels through which it could mount and descend, until the flow is stopped. Then the tree dies. It is not the holes he makes, nor the sap he draws, but the way he places his holes that makes the sapsucker an unwelcome visitor. For an unacceptable individual he is to the farmer,--_persona non grata_, as kings say of ambassadors who do not please their majesties. What shall we do with him, the only black sheep in all the woodpecker flock? Let him alone, unless we are positively sure that we know him from every other kind of woodpecker. The damage he does is trifling compared with what we should do if we made war upon other woodpeckers for some supposed wrong-doing of the sapsucker.

VIII

EL CARPINTERO

In California and along the southwestern boundary of the United States lives a woodpecker known among the Mexicans as El Carpintero, the Carpenter.

Carpentering is both his profession and his pastime, and he seems really to enjoy the work. When there is nothing more pressing to be done, he spends his time tinkering around, fitting acorns into holes in such great numbers and in so workmanlike a fashion that we do not know which is more remarkable, his patience or his skill. Every acorn is fitted into a separate hole made purposely for it, every one is placed butt end out and is driven in flush with the surface, so that a much frequented tree often appears as if studded with ornamental nails. "What an industrious bird!" we exclaim; but still it takes some time to appreciate how enormous is the labor of the Carpenter. Whole trees will sometimes be covered with his work, until a single tree has thousands of acorns bedded into its bark so neatly and tightly that no other creature can remove them.

We may take for examination, from specimens of the Carpenter's work, a piece of spruce bark seven inches long by six wide, containing ten acorns and two empty holes. As spruce bark is so much harder and rougher than the pine bark in which he usually stores his nuts,[1] this specimen looks rough and unfinished, and even shows some acorns driven in sidewise; but for another reason I have preferred it to better-looking examples of his work for study. As we shall see later, it gives us a definite bit of information about the bird.

[Footnote 1: They often use white-oak bark, fence-posts, telegraph poles, even the stalks of century-plants, when trees are not convenient. (Merriam, _Auk_, viii. 117.)]

Think of the work of digging these twelve holes. Think of the labor of carrying these ten large acorns and driving them in so tightly that after years of shrinking they cannot be removed by a knife without injuring either the acorn or the bark. Yet how small a part of the woodpecker's year's work is here! How long could he live on ten acorns? How many must he gather for his winter's needs? How many must he lose by forgetting to come back to them? We cannot calculate the work a single bird does nor the nuts he eats, for several birds usually work in company and may use the same tree; but all the woodpeckers are large eaters, and the Californian has been singled out for special mention.

Can we estimate the amount of work required to lay up one day's food? Judging by the amount of nuts some other birds will eat, I should think that all ten acorns contained in this piece of bark could be eaten in one day without surfeit. The estimate seems to me well inside of his probable appetite. I have experimented on this piece of bark, using a woodpecker's bill for a tool, and it takes me twenty minutes to dig a hole as large but not as neat as these. Doubtless it would not take the woodpecker as long; but at my rate of working, four hours were spent in digging these twelve holes. Then each acorn had to be hunted up and brought to the hole prepared for it. This entailed a journey, it may have been only from one tree to another, or it may have been, and very likely was, a considerable flight. For these acorns grew on oak-trees, and we find them driven into the bark of pines and spruces.

This it is which gives our specimen its particular interest. While oaks and pines may be intermingled, though they naturally prefer different soils and situations, and in the Rocky Mountains the pine-belt lies above the oak region, spruce and oak trees do not grow in the same soil. The spruce-belt stands higher up than the pine. As these nuts are stored in the bark of a spruce-tree, we have clear evidence that the bird must have carried them some distance. For every nut he made the whole journey back and forth, since he could carry but one at a time,--ten long trips back and forth, certainly consuming several minutes each.

Then each acorn had to be fitted to its hole. We have already spoken of the accuracy with which this is done, so that the Carpenter's work is a standing taunt to the hungry jays and squirrels which would gladly eat his nuts if they could get them. A careful observer tells us that when the hole is too small, the woodpecker takes the acorn out and makes the hole a little larger, working so cautiously, however, that he sometimes makes several trials before the acorn can be fitted and driven in flush with the bark. Some of these acorns show cracks down the sides, as if they had been split either in forcibly pulling them out of a hole not deep enough for them, or in driving them when green and soft into a hole too small for them. Of course after each trial the acorn must be hunted up where it lies on the ground and driven in again, and this takes considerable time.

As nearly as we can estimate it, not less than half a day must have been spent in putting these acorns where we find them. With smaller acorns, stored in pine bark, less time would have been required; but weeks, if not months, of work are spent in laying up the winter's stores.

How the woodpecker's back and jaws must have ached! Surely he is human enough to get tired with his work, and it is not play to do what this bird has done. Some of the acorns measure seven tenths of an inch in diameter by nine tenths in length, and the bird that carried them is smaller than a robin. How he must have hurried to reach his tree when the acorn was extra large! Yet he took time to drive every one in point foremost. Even those that lie upon their sides must have been forced into position by tapping the butt. He knows very well which end of an acorn is which, does our Carpenter.

But what is the use of all this work? Why, if he wants acorns, does he not eat them as they lie scattered under the oaks, instead of taking pains to carry them away and put them into holes for the fun of eating them out of the holes afterward? The absurdity of this has led some people to surmise that the Carpenter chooses none but weevilly acorns, and stores them that the grub inside may grow large and fat and delicious. This would be very interesting, if it were true. There must of course be more weevilly acorns on the ground than he picks up, so that he could get as many grubs without taking all this trouble, and there is no reason why they should not be as large and good as those hatched out in holes in trees. When I wish to keep nuts sweet, I spread them out on the attic floor in the sun and air, keeping them where they will not touch each other. The Carpenter does practically the same thing. Is it probable that he tries to raise a fine crop of grubs in this way? If so, one or the other of us is doing just the wrong thing. But if weevils are what the Carpenter wants, then the nuts in the bark should be wormy; yet only two of them show any sign of a weevil, and of these one appears from its dull color and weather-beaten look to be a nut deposited several years before the others by some other woodpecker. Every other acorn is as hard, shining, and bright colored as when it fell from the tree. Evidently the bird picked these nuts up while they were fresh and good; perhaps he chose them _because_ they were good and fresh. The possibility becomes almost a certainty when we observe that naturalists agree that the Carpenter uses no acorns but the sweet-tasting species. Now there are likely to be as many grubs in one kind of an acorn as in another, and he would scarcely refuse any kind that contained them, if grubs were what he wanted. The fact that he takes sweet acorns, and those only, shows that it is the meat of the nut that he wants. And all good naturalists agree that it is the kernel itself that he eats.

Why he stores them is not hard to decide when we remember that the Californian woodpecker, over a large part of his range, is a mountain bird. Though we think of California as the land of sunshine, it is not universal summer there. The mountain ranges have a winter as severe as that of New England, with a heavy snowfall. When the snow lies several feet deep among the pines and spruces of the uplands, the Carpenter is not distressed for food: his pantry is always above the level of the snow; he need neither scratch a meagre living from the edges of the snow-banks, nor go fasting. His fall's work has provided him not only with the necessities, but with the luxuries of life.

But why does he spend so much time in making holes? He might tuck his nuts into some natural crevice in the oak bark, or drop them into cavities which all birds know so well where to find. And leave them where any pilfering jay would be able to pick them out at his ease? Or put them in the track of every wandering squirrel? Jays and squirrels are never too honest to refuse to steal, but they find it harder to get the woodpecker's stores out of his pine-tree pantry than to pick up honest acorns of their own. So, like the woodpecker, they lay up their own stores of nuts, and feed on them in winter, or go hungry.

We have had very little aid from anything except the piece of bark we were studying, yet we have learned that the Californian woodpecker is a good carpenter; that he works hard at his trade; that he shows remarkable foresight in collecting his food, much ingenuity in housing it, good judgment in putting it where his enemies cannot get it, and wisdom in the plan he has adopted to give him a good supply of fresh nuts at a season when the autumn's crop is buried under the deep snow.

If I were a Californian boy, I think I should spend my time in trying to find out more about this wise woodpecker, concerning which much remains to be discovered.

IX

A RED-HEADED COUSIN

Besides his half-brothers, the narrow-fronted and ant-eating woodpeckers, the Carpenter has a numerous family of cousins,--the red-headed, the red-bellied, the golden-fronted, the Gila,[1] and the Lewis's woodpeckers. These all belong to one genus, and are much alike in structure, though totally different in color. Most of them are Western or Southwestern birds, but one is found in nearly all parts of the United States lying between the Hudson River and the Rocky Mountains, and is the most abundant woodpecker of the middle West. This well-known cousin is the red-headed woodpecker, the tricolored beauty that sits on fence-posts and telegraph poles, and sallies out, a blaze of white, steel-blue, and scarlet, a gorgeous spectacle, whenever an insect flits by. He is the one that raps so merrily on your tin roofs when he feels musical.

[Footnote 1: So named from being found along the Gila River.]

In many ways the red-head, as he is familiarly called, is like his carpenter cousin. Both indulge in long-continued drumming; both catch flies expertly on the wing; and both have the curious habit of laying up stores of food for future use. The Californian woodpecker not only stores acorns, but insect food as well. But though the Carpenter's habits have long been known, it is a comparatively short time since the red-head was first detected laying up winter supplies.

The first to report this habit of the red-head was a gentleman in South Dakota, who one spring noticed that they were eating _young_ grasshoppers. At that season he supposed that all the insects of the year previous would be dead or torpid, and certainly full-grown, while those of the coming summer would be still in the egg. Where could the bird find half-grown grasshoppers? Being interested to explain this, he watched the red-heads until he saw that one went frequently to a post, and appeared to get something out of a crevice in its side. In that post he found nearly a hundred grasshoppers, still alive, but wedged in so tightly they could not escape. He also found other hiding-places all full of grasshoppers, and discovered that the woodpeckers lived upon these stores nearly all winter.

But it is not grasshoppers only that the red-head hoards, though he is very fond of them. In some parts of the country it is easier to find nuts than to find grasshoppers, and they are much less perishable food. The red-head is very fond of both acorns and beechnuts. Probably he eats chestnuts also. Who knows how many kinds of nuts the red-head eats? You might easily determine not only what he will eat, but what he prefers, if a red-headed woodpecker lives near you. Lay out different kinds of nuts on different days, putting them on a shed roof, or in some place where squirrels and blue jays would not be likely to dare to steal them, and see whether he takes all the kinds you offer. Then lay out mixed nuts and notice which ones he carries off first. If he takes all of one kind before he takes any of the others, we may be sure that he has discovered his favorite nut. Such little experiments furnish just the information which scientific men are glad to get.

It is well known that the red-head is very fond of beechnuts. Every other year we expect a full crop of nuts, and close observation shows that the red-heads come to the North in much larger numbers and stay much later on these years of plenty than on the years of scanty crops. Lately it has been discovered that they not only eat beechnuts all the fall, but store them up for winter use. This time the observation was made in Indiana. There, when the nuts were abundant, the red-heads were seen busily carrying them off. Their accumulations were found in all sorts of places: cavities in old tree-trunks contained nuts by the handful; knot-holes, cracks, crevices, seams in the barns were filled full of nuts. Nuts were tucked into the cracks in fence-posts; they were driven into railroad ties; they were pounded in between the shingles on the roofs; if a board was sprung out, the space behind it was filled with nuts, and bark or wood was often brought to cover over the gathered store. No doubt children often found these hiding-places and ate the nuts, thinking they were robbing some squirrel's hoard.

In the South, where the beech-tree is replaced by the oak, the red-heads eat acorns. I should like to know whether they store acorns as they do beechnuts. Are chestnuts ever laid up for winter? How far south is the habit kept up? Is it observed beyond the limits of a regular and considerable snowfall? That is, do the birds lay up their nuts in order to keep them out of the snow, or for some other reason?

It remains to be discovered if other woodpeckers have hoarding-places. We know that the sapsucker eats beechnuts, and the downy and the hairy woodpeckers also; that the red-bellied woodpecker and the golden-winged flicker eat acorns; and I have seen the downy woodpecker eating chestnuts, or the grubs in them, hanging head downward at the very tip of the branches like a chickadee. It may be possible that some of these lay up winter stores.

It is known that the Lewis's woodpecker occasionally shows signs of a hoarding instinct. It was recently noted that in the San Bernardino Mountains of California the Lewis's woodpecker, after driving away the smaller Californian woodpeckers, tried to put acorns into the holes the Carpenter had made, but, being unused to the work, did it very clumsily. Soon after this observation was published, a boy friend living near Denver told me that a short time before he had seen a woodpecker that had a large quantity of acorns shelled and broken into quarters, on which he was feeding. This woodpecker was identified beyond a doubt as the Lewis's woodpecker. So we begin to suspect that the habit of storing up food is not an uncommon one among the woodpeckers.

X

A STUDY OF ACQUIRED HABITS

Something interesting yet remains to be discovered of the hoarding habit of the red-head. How strange that so familiar a bird should have a habit so easily detected, and yet that no one in all these years should speak of it! Who does not know how mice and chipmunks hide their food? Who has not watched the blue jay skulking off to hide an acorn where he will be sure to forget it? Who does not remember the articles his pet Jim Crow stole and lost to him forever? The hoarding habit has long been observed of many dull-colored, rare, or insignificant creatures. That one so noisy, gay-colored, tame, and abundant as our red-headed woodpecker should have the same habit and escape observation is certainly remarkable. But though it is over twenty years since the storing of grasshoppers was recorded and twelve since the practice of laying up beechnuts was observed, very little seems to have been learned of the habit since these records were made.

There are two points to be considered: the habit long remained unknown; after it was discovered, it was long in being reaffirmed. It seems that, if it were a general habit, more would be known about it. Now if it is not a universal habit, it must be one of two alternatives, either a custom falling into disuse, or a new one just being acquired. That a habit so remarkable and so advantageous should be discarded after being universal is scarcely possible; that a habit so noticeable, if it were general, should remain unknown is improbable; that a habit which made life in winter both secure and easy should, if introduced by a few enterprising birds, become a universal custom, is not without a parallel. The probabilities point to the custom of hoarding food as a recently _acquired habit_.

Acquired habits are not rare among birds. The chimney swift has learned to nest in chimneys since the Pilgrims landed; for there were no chimneys before that time. There is the evidence of old writers to show that they acquired the habit within fifty years of the time of the first permanent settlements in New England. The eaves swallow learned to transfer its nest from the side of a cliff to the side of a barn in less time. Most birds will change their food as soon as a new dainty is procurable, and they will even invent methods of getting it, if it is much to their taste. The way the English sparrows have learned to tear open corn husks so as to eat the corn in the milk is a good example, for our maize does not grow in England, and they have had to learn about its good qualities in the few years since they have become established outside of the cities. Yet it is already a well-established habit. So quickly does a habit spread from one bird to another, until it becomes the rule instead of the exception! Acquired habits always show adaptability, and often much forethought and reason. It is the shrewd bird that learns new tricks.

Now there is not known among birds any evidence of greater forethought and reason than working hard in pleasant weather, when food is plentiful beyond all hope of ever exhausting it, to lay up provision for winter. How does the woodpecker know that winter will come this year? That there was a winter last year and the year before does not make it certain, but only probable, that there will be one this year. We cannot know ourselves that the seasons will change until we learn enough of astronomy to understand the proof. Nor does instinct explain the habit, as some would declare: since not all red-heads have the habit, though all must have instinct. It would seem as if memory and reason had devised this plan for outwitting winter, the bird's old enemy.

The red-head is not a grub-eating woodpecker. Though beetles make up a third of his food, their larvae do not form any part of it. Half his food for the entire year is vegetable, and the animal portion is composed principally of beetles, ants, caterpillars, and grasshoppers, which in winter time are hidden in snug places, or are dead under the snow. There are few berries in winter. The few seedy, weedy plants that stick up above the snow give to the birds the little they have; but the red-head's vegetable fare is limited at that season and his animal food almost lacking. Winter in the North is all very well for the hairy and downy cousins that like to hammer frozen tree-trunks for frozen grubs; but our red-headed friend does not eat grubs by preference. Rather than change his habits he will change his boarding-place. So he is a migratory woodpecker, though the woodpeckers are naturally home-loving birds, and do not migrate from preference. If, however, he can lay up a store of vegetable or animal food, he can winter in any climate. Hoarding is thus an invention as important to the woodpecker world as electric cars and telephones are to men. The probabilities are that this is a recent improvement in the red-head's ways of living.

Another set of facts increases the probabilities of our supposition. It is a very delicate subject to handle because it affects the reputation of a family in good standing; but there is positive proof that sometimes the red-head has been guilty of crimes which would give a man a full column in the newspapers with staring headlines. If such deeds were not a thousand times less common among woodpeckers than they are among men the red-head would be declared an outlaw. He has been proved to be a hen-roost robber, a murderer, and a cannibal. In Florida he has sucked hen's eggs. In Iowa he has been seen to kill a duckling. There is a record in Ohio that he pecked holes in the walls of the eaves swallow's nest and stole all the eggs, and that he was finally killed in the act of robbing a setting hen's nest. Within the space of fifteen years, from Montana, Georgia, Colorado, New York, and Ontario, in addition to the records mentioned already from Florida, Ohio, and Iowa, come accounts of his stealing birds' eggs and murdering and eating other birds. The evidence is indisputable.

It is charity to suppose that this is the work of natural criminals, or of degenerate, under-witted, or demented woodpeckers. Why should there not be such individuals among birds? One point is certain: so notable a habit could not long escape detection, since it is a barnyard crime. He who robs hen's nests gets caught--if he is a bird. Either these occurrences are very rare, not seen because of their extreme rarity, or they indicate a new custom just coming in. And the same is true of the habit of hoarding food; it is rare, or it is new.

The frequency of such occurrences can be determined only by observation; but the time of their origin might be approximated in another way. If we could fix the date when the bird could not have done what he is now doing for simple lack of opportunity, we might say that the habit has been acquired since a certain date--as we have said of the English sparrow eating maize, of the chimney swift nesting in chimneys, and the cliff swallow building under the eaves. But we have no such help on the case of the red-head, which never has been without opportunities to get birds' eggs and to kill other birds.

But there is a parallel case in another species where the date of an acquired habit can be proved. In Florida the red-bellied woodpecker has earned the names Orange Borer and Orange Sapsucker because he eats oranges. It is true that he is not charged with doing damage, because he attacks only the over-ripe and unmarketable fruit; it is known that the habit is not general yet, for even where the birds are abundant only a single bird or a pair will be found eating oranges, and always the same pair, proving that it is a habit not yet learned by all of the species; close observers declare, too, that it is but a few years since the bird took up the habit; and, finally, we know that this must be the case, for, though the wild orange was introduced by the Spaniards, the sweet fruit was not extensively cultivated until recently. Here is a habit which undoubtedly has been acquired within twenty years or so, which will in all probability increase until instead of being the exception it is the rule.

Why may not the red-head's occasional cannibalism, unless this is mere individual degeneracy, and his more common custom of hoarding be habits that he is acquiring? Why, indeed, may not the Californian woodpecker's distinguishing trait be a habit which began like these among a few birds here and there, wiser or more progressive than the rest, and which in time became general and established? Why may not the two observed instances of the Lewis's woodpecker be examples of a similar habit just beginning? The very differences in their methods point to that explanation. The Lewis's woodpecker that had seen the Carpenter's work tried to imitate him; the one that lived outside his range adopted a way of his own, unnoticed before among woodpeckers, and shelled and quartered his nuts before he stored them.

It is remarkable that these four woodpeckers are cousins; they belong to the same genus, and they have essentially the same structure, tastes, and habits. Why should it be strange if their minds were alike too? if they had a natural bent toward accumulativeness, and a natural desire to try new wrinkles? We are sure that one of them has acquired a new habit within a few years. Why may we not suppose as a basis and a spur to further investigation that the others also are acquiring ways new and strange?

XI

THE WOODPECKER'S TOOLS: HIS BILL

There is an old saying, "You may know a carpenter by his chips;" but, though chips are seldom long absent when a woodpecker is about, can we call the woodpecker a carpenter? Is he not both in his works and ways of working--with the one exception of the Californian woodpecker--more of a miner?

For the carpenter takes pieces of wood, bit by bit, and joins them together till at last he has built a lofty skeleton or framework for his dwelling, which last of all he covers over and closes in; and the tools he uses are saw and hammer. With these alone he could build his house, though it might be neither very large nor very good. When a carpenter's house is finished, it is neither a cave nor a hole, but a pavilion built in the open air after the model of a spreading tree,--which frames a roof with its branches and shingles it with overlapping leaves. There is nothing in the woodpecker's way of building which corresponds to that.

Quite different are the miner's methods. In the West, where the barren mountain sides stretch up into snowclad summits, on the face of slopes as seamed and gray and verdureless as the wrinkled trunk of an aged oak, I have seen holes where human woodpeckers burrow. The entrance to a mine half-way up a hillside looks strikingly like a woodpecker's hole and scarcely larger. Nor does the likeness vanish as we think how in their long tunnels inside their mountains of gold and iron and silver the delving miners are picking and prying and picking to lengthen their burrows just as the woodpeckers peck and pry and peck inside their wooden mountain, the tree-trunk. Which shall we call the woodpecker--a carpenter or a miner?

What are the miner's tools? Pick and drill, are they not? What are the woodpecker's? The same. Certainly we shall see, if we stop to think, that it is not a chisel that he uses, as we sometimes say. A chisel is a knife driven by blows of a hammer; like a knife its effectiveness depends upon the sharpness and length of its cutting edge. But a woodpecker's bill is not a cutting tool. It is a wedge, but a wedge working on a different principle from a knife-edge. Look at this one and observe that, though strong and stout, it is not sharp and has no true cutting edge. It is a tapering, square-ended, flat-sided tool, rather six-sided at the base and holding its bevel and angles to the tip. The woodpecker's bill is a pick, not a chisel. It is used like a pick, being driven home with a heavy blow and getting its efficiency from its own weight and wedge-shape and from the force with which it is impelled. Watch the downy woodpecker at his work and see what sturdy blows he delivers, pausing after each one to aim and drive home another telling stroke. This is pick-axe work. But sometimes he rattles off a succession of taps so short and quick that they blend together in one continuous drumming, too light and quick to be likened to the ponderous swing of the pick-axe. Now he is drilling. The work of a drill is to cut out a small deep hole either by twirling (as in drilling metals) or by tapping (as in drilling stone). The woodpecker drills by the latter method and there is a curious likeness between his bill and the mason's tools.

Any one who has lived in a granite country knows the deep round holes that stone masons make when they split rock. Did you ever wonder why they are as large at the bottom as at the top? If you remember the shape of a mason's drill, you will recollect that it looks a little like a stick of home-made molasses candy bitten off when it was just soft enough to stretch a little. The mason's drill is a round iron rod with a thin, flat end, sharpened on the edge and a little pointed in the centre. In the flattening of the sides and the width across the tip its end resembles that of a typical woodpecker's bill. The woodpeckers that drill for grubs, especially the largest, the logcock and the ivory-billed woodpecker, have the tip remarkably flattened. The likeness to the drill does not go farther because the woodpecker's bill is a combination tool; but it is drill-pointed rather than pick-pointed.

What is the advantage of this compressed tip? Can the bird pick as well as he could with a sharp point? The bird and the mason reap the same benefit from this form of tool. A sharp-pointed drill would bind in the hole and could neither be driven ahead nor removed without difficulty, but the sharp-edged tool cuts a hole as wide as the instrument. There is, of course, some difference between working in stone and in wood, but the principle is the same. The mason strikes his drill with his hammer and cuts a crease in the stone; then lifts and turns the drill, cutting a crease in another direction; and so by continually changing the direction of the cuts until they radiate from a centre like the spokes of a wheel, he finally reduces a little circle of stone to a powder fine enough to be blown out of the hole. In drilling for a grub the woodpecker must do much the same thing. He wishes to keep his hole small at the top so as to save work, yet it must be large enough at the bottom to admit the borer when nipped between his mandibles; therefore he needs an instrument that, like a drill or a chisel, will cut a straight-sided hole. Indeed, we might call it a chisel just as well if it were not a double-wedge instead of a single wedge and if it did not move when it is struck instead of being held stationary beneath the blows.

When he is digging his house the woodpecker uses his bill as a pick-axe. When he is digging for grubs he uses it as a drill. Now some species drill very little and some a great deal, according to the number of grubs they feed on; but all dig holes to nest in,--that is, all use their bills as picks but only a few employ them as drills. The flickers, for example, seldom drill for grubs, their food being picked up on the surface or dug from the earth; yet they excavate the deepest, roomiest holes made by any woodpeckers of their size; they use their bills effectively as pick-axes, but seldom, very seldom, as drills. And what do we find? No drill-point--not a truncate, compressed bill fit for drilling, but a sharper, pointed, rounded, _curving_ bill. Notice the ordinary pick-axe and see how much nearer the flicker's bill than the logcock's or the ivory-billed woodpecker's it is. Why is a flicker's bill better for being curved also? Why do the drilling woodpeckers have a perfectly straight bill? We should find by studying the birds and their food that there is a direct relation between the shape of the bill and the amount of drilling a woodpecker does; that the grub-eating or drilling woodpeckers have a straight bill, for working in small deep holes, while the flickers have a curved bill for prying out chips. And we should note that the flicker's bill is most like the ordinary bill of perching birds, while the drilling bill, as typified by the logcock's and the hairy woodpecker's bills, is a more specialized tool, limited to fewer uses, but more effective within its limits.

There is another detail of the woodpecker's bills which casts light upon their habits. The species that drill most have their nostrils closely covered by little tufts of stiff feathers, scarcely more than bristles, which turn forward over the nostril. The density and the length of these tufts agree very well with the kind of work the woodpecker does; for in the hairy and the downy, which are continually drilling and raising a dust in rotten wood, they are very thick and noticeable, while in the red-head and the sapsucker they show as scarcely more than a few loose bristles, and in the flicker they barely cover the nostril. This seems a plain provision to keep the dust out of the bird's lungs; and we might cite as additional evidence the fact that the only other birds of similar tree-pecking habits, the nuthatches and the chickadees, have their nostrils protected in the same way. But we must always be cautious before drawing inferences of this sort to see what may be said on the other side. When we recollect that the crows and ravens and many kinds of finches, among other birds, none of which dig in the bark of trees or raise a dust, have their nostrils as completely covered, we see that we have perhaps discovered a _use_ for these nasal tufts but not the _cause_ of their being there. We must be careful not to mistake cause and accompaniment in our endeavor to explain differences in structure.

Let us see what we have learned and how to interpret it:--

That the woodpecker's bill is a combination of drill and pick-axe.

That the shape varies with the use to which it is most commonly put.

That the use varies with the food principally eaten; or, what is a step farther back, that the different kinds of food must be sought in different places and by different methods, and therefore require different tools.

Therefore the shape of the woodpecker's bill has a direct relation to the kind of food he eats. Please notice that we do not assert that it _causes_ him to eat a certain kind of food nor that a certain diet may not have affected the shape of the bill, causing it to be what we now see. Both may be at least partially true, but to prove either or both would need profound study, and all that we have observed is that the shape of the woodpecker's bill is _adapted_ to his food and that it varies with the kind of food he eats, or, to be more exact, with his ways of procuring it.

XII

THE WOODPECKER'S TOOLS: HIS FOOT

We have studied the woodpecker's bill and have found that it is a very serviceable tool. We shall find that his feet are equally well adapted to their work.

Here is the foot of a woodpecker. Observe how it differs from a chicken's foot, or a sparrow's foot. What is it that especially fits it for climbing? Perhaps you will notice that the tarsus is short, and you may be able to explain why it would be a disadvantage for a climbing bird to have long legs, as well as why it is a help for him to have long toes. Toes long and legs short is the rule with the woodpeckers.

I never see a woodpecker's foot without thinking of an iceman's nippers with their short handles and long, sharp-toothed jaws. They are designed for similar uses,--to lift heavy weights by laying hold of smooth, flat surfaces. The iceman sets his nippers into the ice and lifts the block; but the bird sets his claws into the tree and lifts his own body.

Suppose the nippers had one short jaw and one long one, would they then take as firm hold as they do with jaws of equal length? In perching birds the hind toe is much the shortest, but they sit balanced upon a limb and have merely to hold themselves in position. The woodpecker climbing a tree-trunk is out of balance; he would fall off unless he had a firm grip; and he could not get this firm hold if his hind toes were not long enough to give his foot a nearly equal spread back and forward. Other birds grasp a limb with the whole under surface of their toes, but the woodpecker when on a smooth, upright tree-trunk nips it only with his toenails. Try with your own hand to hold a stick as large and heavy as you can grasp, and you will see that when you clasp your hand around it as a perching bird takes hold of a perch, it makes little difference that the thumb is shorter than the fingers, but when you try to nip it with your finger tips alone, you must bend your fingers until they are not much longer than your thumb,--that is, a pair of nippers must be equal jawed.

This simple illustration shows why the woodpecker's foot reaches as far backward as forward. But a sensible objection may be raised, namely, that as there are two hind toes of unequal length, it is by no means certain which is the more necessary.

Scientists tell us that a woodpecker's foot, though it looks so unlike a chicken's, is really very much the same. When we ask how one of the front toes disappeared and how the extra hind toe came to be where it is, they tell us that there has been no addition and no loss, but the extra hind toe is only a front toe turned backward. They call it a _reversed fourth toe_. A bird's toes are numbered in order starting with the hind toe and going around the _inside_ of the foot to the outer or fourth toe. The hind toe is the thumb, and the others are numbered in the same order as the fingers of our hands. So we see that the woodpecker's real hind toe is rather small, like that of most birds. It looks very much as if it had been found _too_ small and as if another had turned back to help it do its work. Do you say that a bird cannot turn his toes about in this way? Most cannot, to be sure, but all of the owls can do it. An owl will sit either with two toes forward and two backward, or with three forward and one the other way. The owls have a reversible outer toe, and perhaps the woodpeckers did also before it became permanently reversed.

That this is exactly what had happened is curiously confirmed. There are a few woodpeckers in this country which have but three toes. They are the only North American land birds with less than four toes (though many sea and shore birds have but three). Compare this picture with a four-toed woodpecker's foot. One toe is gone completely, when or how no one can tell. But in some way the _first_ toe, the _thumb_, the one we always begin to count from, has disappeared. The one left is the reversed fourth toe, as we know by the number of joints in it. Undoubtedly this woodpecker needed a hind toe, but he must have needed a longer, stronger one than his natural first toe. A toe of the right length was supplied by turning one of the front toes back, and the short hind toe in some way disappeared.

This may seem a roundabout way to show that a woodpecker's foot is a pair of nippers. First we studied nippers till we found out that they were not good nippers unless they were nearly equal-limbed. Next we studied the woodpecker's foot to learn about that extra hind toe. Then it occurred to us that four toes were not necessary, since some of our best climbers have but three. What was the essential point? Might it not be a foot equally divided without reference to the number of toes? But that is the principle of a pair of nippers. Then came the question, is there any similarity in their use? Yes, the nippers are used to lift heavy weights, and the woodpecker's foot is used to lift his heavy body in just the same way, by taking hold of a flat, smooth surface. We conclude that a wide-spread, equally divided, nipping foot would be the best device possible for the woodpecker's way of living, and we find by examination that every woodpecker shows this type of foot.

There is additional evidence that this is the right explanation. Our only other North American birds that climb on the bark of trees professionally, as we may say, are the brown creepers and the nuthatches. In both these the tarsus is short, as we found it in the woodpeckers, and the hind toe and its claw are fully equal to the middle toe and claw, making an equally divided foot. On the other hand, the foot with two toes forward and two toes backward is confined neither to woodpeckers nor to climbing birds. The parrots, which climb after a fashion, have it; but so do the cuckoos, which do not climb, some of which, like our road-runner, or ground cuckoo of the West, are strictly terrestrial. The "yoking" of the toes may occur by the reversion of the fourth toe, as ordinarily, or of the second toe, as in the trogons; the arrangement appears to be definitely related to the distribution of the tendons that control the toes. But though accounting for the structure may give a clue to its descent, it does not justify its efficiency. The yoke-toed foot is not exclusively a climbing foot. All our families of climbers have at least one representative with but one toe behind, and this clearly proves that the yoke-toed structure is by no means necessary even though it may be an honorable inheritance among climbers. The natural conclusion is that the important point in climbing is not the number nor the arrangement of the toes, but the length of at least one hind toe so as to give an equally divided foot.

There is an interesting point to notice about the woodpeckers. This reversed fourth toe is curiously variable in length. In the flickers, with its claw, it is a little shorter than the middle (third) toe with its claw; in the red-heads and their friends it a little exceeds the middle toe and claw; in the downy and the hairy it is much the longest toe, and in the ivory-billed woodpecker it is abnormally developed. We at once judge that it is some indication of the bird's manner of life, and we look for it to be largest in the species that live continually upon the trunks of trees, obtaining most of their food by drilling. We expect to see the finest development of drilling bill accompany this enormously developed toe, and we find them both in the ivory-billed woodpecker. In imagination we clearly see the use of it. The great bird, keen in his quest of grubs, sidling hastily round the tree, in an unsteady balance and unsupported by his tail, throws one long hind toe downward to steady himself, hooks the other into the bark above him, and hangs between the two as firmly supported as in his ordinary position. No doubt he does do this, but does it prove the supposition that the heaviest and most arboreal woodpeckers have the greatest development of the fourth toe? Not at all. There is our rare acquaintance the logcock, or pileated woodpecker, a bird nearly as large as the ivory-billed, one of the most persistent of our tree-climbers and more than any other woodpecker I ever observed given to scratching rapidly round and round a tree-trunk, clinging at ease in almost any position except head-downward, and drilling incessantly and at all seasons for grubs; he is a typical woodpecker of the largest size, but his hind toe and claw are, if anything, a trifle shorter than his middle toe with its claw. He throws it out and uses it as we have described, but it has not that disproportion to the other toes which we expected to find as the result of a strictly arboreal life.

What have we proved? We have not shown that the long toe is _not_ more useful than the shorter one,--that is a matter of observation; but we have failed entirely to show that it is so, and this can be done only in one of two ways: either by proving that the logcock's habits are not what all previous observers have believed them to be,--which would be assuming a great burden of proof; or by demonstrating that his ancestry explains why his feet do not illustrate our theory,--and this, though it is undoubtedly the true solution, could be settled only by a very learned man.

But we have encountered one truth which must always be held in mind in science--that a theory is not proved while a single fact remains rebellious and unsubdued. We might have examined every other woodpecker in the continent but just one; we might have seen that every other one agreed with our theory, as it does; we might have supposed that the explanation was good past doubting; but that one exception--if it was a logcock--would still over-turn the whole theory; and the very facts that we relied upon to strengthen us--its resemblance in size, habits, shape, and color to the ivory-billed woodpecker--have been the strongest possible means of totally demolishing our fine theory. We have learned, if nothing more, that all the facts must be examined and accounted for before an explanation is accepted as indisputable.

XIII

THE WOODPECKER'S TOOLS: HIS TAIL

If we study the woodpecker's anatomy and observe his broad, strong, highly-arched hip-bones and the heavy, triangular "ploughshare" bone in which the tail feathers are planted, as well as the stiffness and strength of the tail itself, we must conclude that it is not by accident that he uses his tail as a prop. The whole structure shows that the bird was intended "to lean on his tail." What we wish to discover is how good a tail it is to lean on.

Our first impression is that the woodpecker's tail might be improved. Why are not the tips of the feathers stiffer? Why is it so rounded? Most of the work seems to fall on the middle feathers, and in some species, as the downy and the hairy woodpeckers, these end in decurved tips so soft and unresisting that they seem quite unfit to give any support. Would it not be better if the woodpecker's tail had been cut square across and made of feathers equally rigid and ending in short stiff spines? For we see that the woodpecker's tail is not only weak in its inner feathers, but weaker still in its outer ones, and it is stiff, in most species, only in the upper three fourths of its length.