WAYS OF THE WILD.

Auckland Star, Volume LXVI, Issue 170, 20 July 1935, Page 1 (Supplement)

WAYS OF THE WILD.

SEA BIRDS. THEIR ECONOMIC IMPORTANCE (By A. T. PYCROFT.) First in the economic importance of bird products to man is guano. r Guano is the accumulation of their excrement under certain conditions. The best guano from the islands of the Pacific coast of South America has a nitrogen content thirty-three times that of farmyard manure, and it is much more effective as a fertiliser in agriculture than any synthetic compound that has been devised. The trade in this product has been described by Dr. R. C. Murphy, in his book on the subject, as "the greatest modern industry based upon the conversation of wild animals," and on this account some further reference to it will not be out of place. There is a curious chain of circumstances involved, which illustrates the complexity of the web of life. The west coast of South America is washed by the Humboldt current, a great stream of cold water forming part of the Antarctic drift. For a variety of reasons the waters of this ocean stream are peculiarly favourable for the multiplication of those minute unicellular algae called diatoms. These make possible the existence of immense quantities of fishes, and these in turn form the food of vast numbers of birds. Great nesting colonies of seafowl are thus found on the islands, and as these are barren and unwashed by the rain, the guano accumulates in great deposits. The chief guano producer is the guanav, or white-breasted cormorant, but there are also two species of cooley or gannet, and a pelican. The birds breed in milions and their nests may number three to the square yard. The availability of. this fertilising matter is singularly appropriate, because it is indispensable, together with irrigation, for the cultivation of the desert coastal region of the neighbouring mainland. For this purpose it was used by the Incas before the conquest. They worked the deposits in a conservative manner, and strictly protected the birds. The lesson had to be learnt again, nevertheless, for when the value of guano was realised in Europe in the middle of last century an era of reckless exploitation began. The accumulation of ages was rapidly used up, while at the same time the productive birds became greatly reduced in numbers both through disturbance of their nesting places and by direct destruction. Before it was too late the industry was placed under control by the Peruvian Government, and extraction is now limited in amount and regulated by a system of rotation. With protection against human and natural enemies the birds have rapidly repopulated their colonies and the industry prospers while building up its future as it goes.

Birds Make Human Life Tolerable. The indirect economic importance of birds is enormous. The indirect effect of this influence has for the affairs of mankind an importance -which can scarcely be exaggerated. It may be said that without birds both wild plant life and agriculture would become prac'tically impossible, and human life would in other ways be rendered intolerable. Birds provide the best natural check upon the undue multiplication of insects and, to a lesser extent, a check upon that of small mammals and various other forms of animal life. Insectivorous birds, and the species which subsist wholly or largely upon insects, are legion, are indeed the best friends of man in wild Nature. Aquatic species may levy toll upon fishes which are valued by man -for food or sport, or they may be merely neutral in their action. On the other hand, they may be beneficial to fisheries by killing predacious species of fish or other forms of animal life in the water which prey upon the eggs and young of fishes. In the sea it is open to question whether even those species which take large quantities of useful fishes exert an influence upon fisheries which is serious in proportion to the vast natural resources available and to the drain upon those of man himself. Bird life as a whole is undoubtedly beneficial to human interests in the highest degree. Taking species separately, most are either wholly or largely beneficial or are merely neutral in their influence. Only a very few can be classed as altogether harmful. It is not, moreover, always possible or even easy to pass judgment in any given case. A war of extermination was begun against the cormorants frequenting the Murray River, under the impression that they were spoiling the fishing. The result, as it proved, was that the fishing grew worse instead of better. It was then discovered that the birds fed largely upon crabs, eels and other animals which destroyed the spawn and fry of the desirable fishes. The cormorants were therefore a necessary part of the economy of Nature, even from the human, utilitarian point .of view. They were to be classed as beneficial to man in spite of any toll that they might themselves levy upon the aquatic harvest which they had contributed to keep in existence. Over and over apain in his attempts to interfere with Nature, man has been presented with lessons of this kind.

Man's Interference. Great as are the direct reactions of mankind upon bird life, the indirect influences are undoubtedly still _ more important on the whole. No species, of course, can hold out indefinitely against unremitting persecution. The nl ? serious reactions of mankind upon " ir life are those which are due to the effect of civilisation upon the natural haunts of many species. Building ana cultivation have changed the aspec o some countries. Forests have been cleared, swamps have been drained and open land has been broken up and enclosed. Thus the natural haunts of birds of certain habits have been o a abolished throughout wide regions of the earth's surface. By the destruction or alteration of their proper environment, birds are more certainly exterminated from a given are." than by almost anv other means. The direct actions ot man towards birds tend to affect most seriously those species which are deemed hostile to his interests. Xet with all these actions, direct and indirect, favourable and unfavourable, the power of the hand of man for good or evil must not be exaggerated. Long before the appearance of man upon the earth, species were dying out, while others arose to prosperity in their place, often only to wane again. Long before increased population, improved weapons and the processes of modern civilisation had taken effect, the balance of bird life was in a continual state of flux, always being upset by some new factor and" always in process of adjustment to a new point of equilibrium. Man has violently disturbed the balance by the introduction of important new factors into the scheme of things. But he does not control it, except in relatively minor ways, for the forces of i Nature are still at work.