The importance of bird life: a popular account of its economic significance and conservation

Preface

Coal- and iron-mines are largely responsible for rapid development of the United States. From California, Nevada, Alaska, and elsewhere vast deposits of gold, silver, copper, lead, a multitude of metals, some precious and others base though valuable, have presented enormous wealth to our country. Our great subterranean lakes of oil have made possible the expansion of the gas-engine and the automobile to their present state of efficiency. For centuries the banks of Newfoundland have filled our markets with fish. To the forests of Maine, Michigan, Wisconsin, and Oregon we owe a debt for timber which can never be repaid. From Alaska come sealskins, fertilizer from the phosphatic accumulations of the Carolinas and Florida, wild hay from the prairies, and so on through the mile-long list. The resources of America are immeasurable.

But, while we prick up our ears upon being informed that this fishery produces so many tons of fish worth so much, or that from that oyster-bed may annually be taken ten million oysters, or that so-and-so’s manganese-mine accounted for a hundred car-loads of ore last year, we show little

PREFACE interest when we are told that a sparrow hawk captures ten score field-mice a year and innumerable grasshoppers. Yet those very sparrow hawks save the American farmer considerably more than the combined worth of the fishery, the oyster-bed, and the manganese-mine together.

A large amount of valuable matter has been written on the economic relations of birds to agriculture, their relation to man as game birds, domesticated fowl, producers of guano, ornamental plumage bearers, cage birds, and food. But each of these is a specialized field and has been treated separately as such. One to obtain information concerning the agricultural value of birds is compelled to turn to a treatise on economic ornithology; for their domestication you must pursue a poultry book; other volumes deal with game-birds and game-laws, with cage birds or ornamental plumes.

In the following pages the author has endeavored to discuss the importance of bird life to mankind in all its economic phases. Owing to lack of space, he has not laid particular stress either upon its effect on agriculture or upon the domestication of the fowl. These are admittedly the most important functions of bird life from man’s point of view and have been largely dealt with in other volumes. The author contents himself with rather a brief résumé of these functions and passes on to less notable, though highly important, fields.

PREFACE

In collecting material for this volume the author _. acknowledges special indebtedness for the publica- _ tions of the State Conservation Commission of _ New York, the Board of Game Commissioners of the Commonwealth of Pennsylvania, the Department of Agriculture of the Commonwealth of Massachusetts, and the United States Department of Agriculture. He here desires to thank Dr. William T. Hornaday, director of the New York Zoological Park, and Lee S. Crandal, curator of birds at the same institution, for their personal interest and aid in his work.

G. Inness Hartuey.

Southampton, Long Island, July 1, 1922.

Contents

CHAPTER PAGE

INDEX .

LIST OF ILLUSTRATIONS

Chapter I

1. Population. 2. Natural Enemies. 3. Destruction of Insects. 4. Effect on Vegetation. 5. Destruction of Vertebrates. 6. Minor Relations. 7. Summary.

bs Population

Quite the most obvious of all the laws of nature is the one that requires all living organisms to consume food in one form or another to enable them to survive and multiply. This food as a general rule consists of other living organisms. Plant life alone is able to obtain sustenance directly from the chemical elements of the soil.

Deer, for instance, relish as food the blades of grass; but the wolf and certain other carnivorous beasts equally relish the flesh of the deer. And it is fortunate for the welfare of the grazing race that thisis so. Without a host of deadly enemies, 3

—including disease, climatical alterations, and the elements, as well as living creatures,—deer theoretically would multiply at such a rapid rate that the North American continent would be overrun within a few decades. The soil could not produce sufficient fodder for their needs; the verdure would be grazed to death. As a result, the deer would starve: the species would die out, exterminated by its own prolificacy.

One of the chief instruments chosen by nature to combat this excessive production is the earnivore; and the deer, however paradoxical it may sound, is really saved by its most feared and deadly enemies. The Balance of Nature is maintained, and it is this Balance which permits the world to carry on where otherwise it would choke itself to death.

Like the deer, birds, if permitted to multiply unmolested, would increase at an appalling rate, four or five times faster than the animals. The avian class by so much the sooner would become extinct through overpopulation. Fortunately for the world in general, unless man is the exterminator, such a catastrophe cannot overtake us. The natural enemies of birds are far too numerous to permit of so rapid an expansion.

Despite these enemies, birds survive in untold multitudes. It is due to their superior mode of travel that they are so universally scattered over

Z 7 the land surfaces of the earth. There exists _ scarcely a single sea-swept rock, sand spit, or coral _-key which is not the home of some form of feathered life. The north and south polar regions, _ during their respective summer seasons, are overrun with countless hordes of geese and penguins. The mountain tops have special species of their own. The Sahara Desert is populated with a few small birds and a multitude of vultures. Even the oceans boast of a winged fauna of albatrosses, _ phalaropes, gulls, and petrels.

Not only have birds world-wide distribution, but their species are the most numerous of all vertebrated animals. Insects and mollusks, alone of all the animal kingdom, surpass them in this respect. To-day there are known to exist about 19,000 species and subspecies of birds, and numerous newly described forms are annually being

_ added to the list. Against these may be named in the scientific calendar something more than 15,000 species of fish, about 1000 of amphibians, roughly 3500 of reptiles, and of mammals, the class which we commonly associate with the greatest number of forms of all, only 4500!

Of the now existing continents, South America, with its gigantic rain forest, contains the most varied bird fauna. Upward of 5000 racial forms have thus far been described from there, and probably when the entire region has been exploited several thousand more will be added. In North America there are about 1200 forms listed. Europe, Asia, Africa, and Australia are rich in forms, but a combined census—minus a thousand or two island subspecies—shows them to contain altogether scarcely more than the two continents of the Western Hemisphere.

Although fish lead in actual total number, birds make not a bad second when compared with the comparatively meager numerical strength of the remaining vertebrates. We know that seventy years ago hundreds of thousands of bison roamed the plains of the West in herds so vast that they extended beyond the horizon. Within the present generation, even to-day, fifty and seventy thousand caribou may constitute a single herd on the frozen prairies of northern Canada and Alaska. Audubon, however, in 1813, observed a flock of passenger pigeons which took three days to fly past a certain point!

There were more than two and a quarter billion pigeons in that one drove. ‘‘The air was literally filled with Pigeons, the light of noonday was obscured as by an eclipse... .’’ Stefansson, the arctic explorer, tells of Banks Island and neighboring lands several hundred miles north

1 Racial forms as opposed to species are geographical subdivisions of the latter, generally diverging from the type in color, size, or both. Thus, for example, there are described twenty-two races, or subspecies, of the common song sparrow. (Melospiza m. melodia), all found in North America.

of the arctic circle as being ‘‘white with millions of wavy geese’’ (perhaps snow-geese) in the

_- breeding season. Good authorities state that nine

- million penguins inhabit Dassen Island off the _ Cape of Good Hope; and R. C. Murphy, of the

_ American Museum, speaks of almost a million cormorants living on a tiny island off the coast of Peru. While it is difficult to visualize these millions without seeing them, they nevertheless react as a vivid contrast to the puny thousands of bison and caribou.

Therefore, because of their almost universal distribution and the incalculable numbers in which we find them, it is not at all surprising that birds play a major part in the really small cosmos of our planet. Theirs is a great mission, a mission which is undertaken with the utmost diligence and courage. Inalarge measure they preserve the Balance of Nature, in that they check the swelling hordes of insects, control the spread of plant life, replant denuded land surfaces, and extirpate or control the small vertebrates that first ravaged the vegetation of the world and then turned their attention te the crops of mankind. They are a powerful factor.

2 Natural Enemies

Among the natural enemies of birds disease probably holds a far more important position than

= = is generally supposed. Social species, those that live in flocks, are particularly subject to its ravages. Thousands of crows die each year in a single roost from the effects of a virulent throat and nostril malady which may possibly wipe out the entire community. There is a ‘‘grouse disease’? in Great Britain which has accounted for tens of thousands of game-birds. Others are attacked by a form of tuberculosis, and great numbers of sandpipers each spring are left behind on their northerly migration from South America because of diseased sexual organs.

Changes of climate and storms also take an appreciable toll It has been said by more than one good authority that an icy winter kills more game-birds than all the human hunters combined. This statement, in the present day of millions of eager gunners, perhaps is stretching the actual facts, but there is no reason to doubt that entire coveys of bob-white quail and other gallinaceous fowl are frozen stiff in cold, sleety weather. Land birds driven to sea by storms during their migrations have been known to succumb in thousands. This is one of the causes, though probably not the true one, given for the sudden disappearance of the passenger pigeon. Still other birds, unable to migrate south in the winter because of disease, injury, or old age, starve to death.

Certain species do not leave the temperate climate in which they are born. In the winter

Courtesy of Dr. R. C. Murphy

A MILLION BIRDS ON ONE ISLAND

Courtesy of Dr. R. C. Murphy

THE ROOKERIES LIE LIKE DARK SHADOWS OF IMMOVABLE CILLOUDS ON THE SLOPING EXPANSES OF ROCK, WHITENED WITH CHALKY GUANO

~ months they become the prey of a host of predaceous creatures. When the soil is frozen and the field-mice are safely burrowed in their warm winter nests, then goshawks, Cooper’s hawks, sharp-

_ shinned hawks, horned owls, and others descend _ upon the weaker members of the bird tribe. An occasional rabbit is added to their menu, but gameand song-birds are their choicest morsels. They take a fair toll in the spring and summer months, but alleviate it somewhat with mice and other small rodents.

Hawks and owls are not the only creatures that prey upon the less ferocious species. Keeping them company are the ‘‘vermin,’’ individually known are weasels, skunks, lizards, snakes, and the like. A fox seeks out a bird as it would the daintiest titbit. Cats of the tabby variety, which have long forgotten the meaning of a home hearth, utilize them as a staple article of diet. Lizards wax fat on their eggs, as do snakes of many varieties.’

Nor are ‘‘vermin”’ and a few species of hawks and owls the only animal enemies of bird kind. To acertain extent the birds war upon themselves. Crows and jays rob a nest of its eggs or young as much to satisfy their marauding instincts as for food, and they are not averse to raiding the home of one of their own species: they do considerable damage. Where there are large colonies of breeding cormorants and other sea-birds, gulls reap a rich harvest of eggs and nestlings. Condors, until driven off by watchmen, created much havoc among the great guano rookeries of Peru. Skuas hold the penguins of anarctic regions in check.

From the foregoing it would seem as if the odds against survival are so overwhelming that birds will soon be but memories of the past. The limiting barrier, however, is not so mighty as it appears. Birds as a whole are extremely prolific. When matured, owing to their power of fight, they are difficult of capture. Finally, they carry on a not ineffective strife with their enemies, inflicting at times as much damage as they receive. Thus, while certain hawks and owls prefer a diet of bird flesh, others, like the red-tailed or so-called ‘‘hen-hawk,’’ the American sparrow-hawk, and the majority of owls, subsist mainly on ‘‘vermin’’ in its varying forms. Some kites and another ‘‘hen-hawk,’’ the red-shouldered species, delight in the flesh of lizards and snakes. Harmful rodents, such as field-mice and rats, all of which will break into a succulent egg with pleasure, are mainly kept within bounds by the birds.

Being thus able to hold their own, birds play no mean part in the economic relations of mankind by limiting the rodent pests which destroy crops; but this is of comparatively small moment in the broader’ field of Nature. Birds have a greater

_ mission: like the weasel and the fox in their own _ world, they are the spoilers of the insect world.

3 Destruction of Insects

Insects are fair game. Finches and game-birds subsist mainly on seeds—weeds, acorns, or grain, as the case may be; robins and catbirds enjoy a juicy cherry or a luscious strawberry; parrots and toucans consume tropical fruit in enormous quantities; but all of them will swallow an insect with avidity, be they song sparrow, partridge, robin, or toucan. A beetle to a bird is like a drop of nectar to a honey-bee, to be consumed immediately without the loss of a second. Certain species survive wholly upon insects; insects are essential to the diet of most others, particularly in ' the nesting season when the young are to be fed. Night-hawks, swifts, and swallows live virtually on them alone. Grasshoppers furnish much of the daily fare of turkeys. The American sparrow-hawk prefers a grasshopper above anything else as food. .A wood-duck will swim far for the larva of a dragon-fly. A hummingbird devours microscopic insects by the hundred at a meal. The importance of insect destruction cannot be overestimated when we stop to consider the potential possibilities of the tiny organisms. Let : it be understood that there are some four hundred thousand species already recognized, and virtually all are capable of multiplying at an appalling rate.

With this great potentiality for reproduction, then, insects cannot be allowed to go unchecked; otherwise within a short time, the surface of the earth would be a wasted desert. Fortunately nature has provided a multitude of enemies, more, indeed, than birds ever dreamed of having. Thus, the mycelium of certain fungi (the threadlike body of the plants) thrives on the bodies of certain insects; diseases blight them; frost and flood cut short their lives; animals, like the anteater, make of them a sole source of food; parasites flourish and grow fat upon them; they wage continual war among themselves; and birds destroy them—parasites, predaceous forms, and all.

But while this form of destruction is perhaps the greatest mission of birds in nature, it also is of the highest economic importance to agriculture and will be discussed more at length in the next chapter.

Effect on Vegetation

The next great avian function falls under two apparently opposite heads: the limiting of vegetation and the spreading of vegetation.

Limiting of vegetation is confined to the destruction of fruit and seeds. Birds excel in this. Enormous quantities are annually done away with. Much depends upon the type of fruit, whether its mere digestion will serve to kill the enclosed seed, or whether the seed will pass un-

-scathed through the intestines and emerge ready to germinate. If the fruit happens to be unripe the seed naturally seldom survives. Although birds each year consume millions of tons, they do not succeed in rendering all the seeds sterile. A large proportion, especially seeds of berries, live to germinate after they have been evacuated. On the other hand, a great number of weed seeds are destroyed.

It has been determined by experiment that the vegetarians among birds fall into three natural groups. The first is made up of those species which grind and break up the hardest fruits and seeds in their gizzards by the aid of pebbles and gritty sand. Among these are the gallinaceous fowl (e.g., turkeys, grouse, quail, and domestic fowl), pigeons, ducks, titmice, sparrows, and most finches. The smaller birds crush the seeds in their bills before swallowing.

The next group is partly composed of crows, ravens, jackdaws, and jays. Hard-coated berry seeds and cherry-pits pass uninjured through their intestines or may be evicted through the mouth, but soft-skinned seeds are utterly destroyed.

Thrushes form the third group. These do not retain the seeds for long after swallowing the fruit containing them. As quickly as the pulp is disposed of, the seeds are rejected through the mouth before they can pass from the crop to the gizzard. :The small seeds, however, travel through the intestines, with the result that about 80 per cent. are afterward capable of germination. Likewise all hard seeds which pass through members of the second group germinate, but none from the first group. The finches in the United States daily destroy sufficient weed seeds to earn for them the eternal gratitude of the country.

But in the same way, while the finches are destroying their daily millions, more millions are being scattered broadcast by the other groups, to take the place of plants which have succumbed to ~ time or malnutrition. This brings us to birds in their character of planters.

Four-footed animals, the nut-storing squirrels and berry-eating bears for example, play an active part in the spread of plant life, but birds by all odds are primary factors. Crows, jays, and woodpeckers are responsible for far more dispersal of seeds than they are commonly given credit for. They store great heaps of nuts like squirrels; they hide them singly in ecrevx gg NV Aer GE ices of the bark, or collectively under logs; or they drop them miles from the parent tree. The nuts sprout, take root, and perhaps mature in a spot where wooded plants never grew before.

It is not rare to notice an old disused field, forsaken by the farmer because of its barrenness, covered with a scattering of young oaks, hick- - ories, sycamores, and the like. Each year adds to its new flora. Field-mice and other small rodents are responsible for some of this, and the wind has played its part; but birds have been the chief conductors. To them are due the blackberries, the strawberries, and the trailing dewberries. The wind brought the sycamores, the willows, and the maples, but the acorns of the oaks were transported by the birds.

Although, as has been stated, a certain number _ of seeds are expelled from the mouth, the gener- ' ality pass through the intestines before evacuation. Seeds may thus be distributed abroad as the bird flies, or when it perches. The presence of a large number of hedge-rows is due to the latter event. The American farmer does not make a common practice of planting hedges between fields. He is constrained to erect a fence, post and rail, stone, or wire, as he sees fit or the resources of the locality allow. His live stock have to be kept within bounds; a hedge is ineffective for this purpose.

Unless, however, the farmer maintains a cony tinual guard with brier hook and scythe, a hedge invariably does spring into being along the fence line. Almost before he realizes it, there will arise a well defined row of junipers, chokecherries, sassafras, a conglomeration of a dozen species perhaps, and banked by dense growth of blackberries, wild raspberries, or sumacs. As none of these spring from wind-blown seeds, birds must be the carrying agents, or, if it be a stone fence, chipmunks, perhaps, and birds.

Again, certain plants owe their very existence to the agency of birds. To the fruit-pigeons is attributed the spread of wild nutmegs over New Guinea and the surrounding islands. The pigeons swallow the fruit for the sake of the red ‘‘mace’’ which covers the seed, and later throw out the hard pellet through the mouth as robins do cherry-pits, or expel it with their feces.

A more striking example of entire dependence is the case of the mistletoe. Living only as a parasite on trees, the seed must be deposited in a crevice of bark before the plant can develop. The white viscous berries are eaten only by birds, who later evacuate the seeds freed of pulp. If this occurs while the bird is perched in a tree, the excrement runs down over the branch and the seeds find a lodgment for later germination.

Further distribution of plant life may occur from the mud which sometimes adheres to the feet. Such an eventuality is particularly prevalent among species like the woodcock and marsh birds which live in muddy areas. Darwin was able to rear eighty-two plants from a single ball of earth

_ adhering to the foot of a partridge. The rough- _ ened shank of the large tinamou of South America carries an appreciable amount of earthy material lodged in the crevices of its rear scales. This forest mold ordinarily contains seeds.

Birds are beneficial to vegetation in other ways. The hummingbird, for instance, aids in the cross-

_ pollination of blossoms by carrying pollen in its feathers from one flower to another. This holds true for other species, but as the work would be carried on by insects if birds were not present their efforts cannot be assumed to play an essential part in cross-pollination. On the other hand, ripened seeds like beggar’s-lice and cockles are specially constructed to adhere to feathers and

' fur, and may be carried a long distance before their hosts can free themselves.

Once more, considerable dispersal of vegetation is due to birds of prey. The osprey when it plunges after carp or perch often clutches a talonful of water-weeds as well as its intended quarry. These are sometimes transported to a tree that overhangs another body of water. There, while the osprey consumes its catch, the weeds drop down into the new water. At the same time the contents of the fish’s stomach drip into the lake, carrying great numbers of minute aquatic plants and often seeds. Similarily, when a Cooper’s hawk devours a granivorous bird, the material in the crop of the victim is _ scattered upon the ground, or is expelled later in the feces of its slayer.

5 Destruction of Vertebrates

Having touched slightly upon insects and discussed the subject of limitation of vegetation, we now arrive at the third mission in which birds hold a trump ecard. This is the suppression of vertebrates.

Although the destruction of rodents properly falls in the field of economics and will be discussed at greater length in the next chapter, birds have an effect on other vertebrates which warrants a place here. Large hawks, eagles, and owls exert considerable influence over the home life of many medium-sized animals. The hawkeagles of South America subsist almost wholly upon monkeys and other mammals that inhabit the roof of the jungle. In other parts of the world eagles capture fawn, young antelope, sheep, goats, and even young wild pigs. Nor are reptiles exempt. The secretary-bird of South Africa is closely protected by law because of its fondness for poisonous snakes. In our country,

~ besides several hawks that prey upon snakes and lizards, the turkey-vulture exhibits a fondness for the eggs of alligators, a habit which serves in some measure to hold those reptiles within proper bounds.

Sea-birds are harbingers of destruction to the fish group. Most of them live entirely upon fish. Gulls, albatrosses, and fliers of that type annually devour millions of tons. Other than these, there exist numerous colonies of fish-eating cormorants, boobies, and pelicans, to say nothing of penguins, auks, and sea-ducks. A single colony sometimes consists of hundreds of thousands of individuals, even of millions. So plentiful are the cormorants and other water-fowl of the St. Lawrence Gulf that they darken the face of cliffs already whitened with their exereta. And the St. Lawrence is only one of . many similarily infested regions of the earth.

Parts of the antarctic continent form another area with its millions, as do the coasts of Alaska, Labrador, and Peru, and every one of the aquatic birds that live there is a fish-eater. Allowing one pound of fish a day to a cormorant,—a low estimate,—we can reckon that a small colony of 100,000 birds will consume fifty tons, or virtually two full carloads, every twenty-four hours. With the million upon million individuals of this single family in existence, and other millions of their kindred with even more voracious appetites, it is evident that their combined daily toll is enormous.

When compared to that of aquatic birds, the damage done to the fish tribe by such species as the osprey and the kingfisher is slight. It is appreciable, however, when we remember that they confine their operations to small bodies of water which of necessity must have a limited aquatic population. Thus, kingfishers carry havoe among the minnows and small fry of lesser waterways and ponds, and therefore no longer receive protection from the law. But, despite their depredations, their part in the great balance is as much to spread life as to curtail it. Barren pools are stocked with fish by kingfishers. Although a fish normally will seldom escape an osprey when once gripped in its talons, under sudden stress the hawk will drop it; if, for instance, he is beset by a swarm of crows or martins, he may be forced to drop his load in order by flight to save himself from persecution. Many isolated ponds and lakes have been stocked by the agency of these birds.

6 Minor Relations

Although disease sometimes sweeps through a colony of birds, exterminating it to the last member, it is doubtful if they can communicate the disease to another species. Hvidence on this

- score is meager and wholly unconvincing. It is possible, however, for them to carry the germs of a disease, with which they are not themselves impregnated, from one animal to another. The most outstanding case of this kind is that of the turkey-vulture and the pig. The vulture is a scavenger, pure and simple, and feeds wherever it can find carrion. To one of these birds a pig which has recently succumbed to cholera is as succulent a morsel as one which has died of old age. The vulture can see no difference. Consequently, upon leaving the skeleton, it carries off upon its body and feathers a multitude of deadly germs. 4 . The result is easy to follow. Upon alighting in a piggery, perhaps miles distant from its recent activities, the vulture unwittingly scatters the germs broadcast, either through excretion or by coming into contact with an object to which they will adhere. If pigs are present they will become inoculated. The remedy of course lies with the farmer; he should bury his dead stock. It has more than once been claimed that birds are partly responsible for the spread of the chestnut blight which of recent years has devastated the chestnut forests of the United States. This is not at all improbable. The blight is a fungus disease which works on the inner, or cambium, layer of bark. The spores are exceedingly minute and may be wafted long distances by the wind. Great numbers may also be transported from grove to grove and forest to forest hidden in the feathers of birds, just as the humming-bird carries pollen.

- Among other minor relationships which may have a bearing on the general balance is the continual association of some species with large four-footed beasts. For example, we have in America the cowbird which has contracted a habit of following a herd of cattle about a pasture to feed upon the flies attracted by the animals. The cowbird, however, seldom or never alights upon the cattle themselves as does that strange black cuckoo of South America, the ani, and the starling-like rhinoceros-bird of Africa. These have an especial fondness for ticks and other body parasites which abound on all beasts free from the curry-comb, and they take a small but valuable part in the life history of the animals they attend. Unfortunately, the rhinoceros-bird, with the coming of domestic cattle into South Africa, has fallen into disgrace. In tearing a tick from its hold on the back of its host, the bird generally causes a small wound in the tender hide, which soon grows infected. The rhinoceros-bird of late years has also become endowed with a taste for blood, and now inflicts wounds where there are no ticks at all.

t Summary

To summarize briefly: The greatest function of birds in nature is the utilization of their vast numbers to aid in the maintenance of the great Balance. Their chief mission is to check the spread of insects. They help to hold within bounds the spread of vegetation and at the same time oversee the establishment of plant life in localities where it has been uprooted or is absent. Through their efforts the enormous shoals of fish are limited, and barren pools are stocked. They reduce the number of crop-destroying rodents. They act as food for the support and growth of other animals.