Importance of Birds to Agriculture and Forestry in New Zealand

Forest and Bird, Issue 88, 1 May 1948, Page 7

Importance of Birds to Agriculture and Forestry in New Zealand

By

L. W. McCASKILL,

M.Agr.Sc.

WHEN trying to assess the economic value of birds and balance the good they do to man against the harm done we are inclined to forget something about birds which cannot be measured in bushels of grain or in pounds, shillings and pnece. That something can be summed up in two lines of Emerson: “If eyes were made for seeing - Then Beauty is its own excuse for being/’ Birds have been the inspiration of much that is fine in our art, poetry and song and even if they had no economic value whatever they would still deserve our study, encouragement and. protection. Agriculture is unnatural. . In primeval times, when man was a nomad, there had developed a balance between the wild plants, the insects which fed on the plants and the birds which fed on both plants and insects. When man first scratched the soil with a stick and sowed wild, seed in the furrow he unwittingly embarked on an enterprise contrary to all the rules of nature. As a farmer he concentrated innumerable individuals of the same kind of plant in orderly rows as against nature’s method of dividing up the space amongst numerous competing kinds. He provided not merely an opportunity but an open invitation to vegetable feeding animals such as insects. Right through the ages insects have been responsible for more damage to farm and orchard crops than all other known organisms but it has taken man a very long time to learn that this damage would be very much greater if it were not for the insectivorous birds. There have, of course, been many spectacular examples of birds joining to the rescue of man

when his crops have been attacked by plagues of locusts or caterpillars. The one which received tangible recognition in the seagull monument in Salt Lake City, Utah, is perhaps best known but we are inclined to forget in New Zealand that it was the introduction of English birds in the sixties and seventies to deal with the plagues of caterpillars here which made agriculture possible in this country. But the destruction of suddenly arising insect swarms is not the chief function of birds as far as agriculture is concerned. Their mission is rather to exert a steady pressure on insects as a whole. Unfortunately the harm birds do is more obvious than the good. We always know when birds steal grain, rob poultry, eat fruit and seedlings. We do not find it easy to measure the amount of good they do by eating harmful insects. Our scientific research into this matter is very much behind that of other countries, especially the United States and until we have an organisation set up to give us accurate information, we would be unwise to enter on any campaign of wholesale destruction of allegedly harmful birds. No matter what we may think about certain introduced, species such as the sparrow and the blackbird we should realise that the native species found on our farmlands are entirely useful, and with only one or two exceptions are absolutely protected. As regards birds and forests in New Zealand we have very little room for doubt. WITHOUT OUR FOREST BIRDS OUR FORESTS SIMPLY COULD NOT EXIST. If you make careful observations of these bush birds and study their habits and methods of feeding you will find that their useful work for the forests can be divided into three sections, the checking

of insect pests, the pollination of flowers and the distribution of the seeds of trees and shrubs.

Of the 36 kinds of our birds which are predominantly forest dwellers, 28 subsist either wholly or in part on insects. Careful study shows that all the available habitats of insects have been carefully parcelled out among the various groups of birds. Thus the forest floor is the hunting ground for the kiwi, the weka, the robin and the tomtit; on the trunks and larger branches you will find the wrens, especially the rifleman, and the saddleback and kaka; the twigs and leaves are carefully searched by the brown creeper, the bush canaries and the warbler; while the air is left to the black and pied fantails. 7

Most of our trees and shrubs are pollinated by the wind or by insects but some important trees need birds to perform this function. Among them are the northern and southern ratas, pohutukawa, puriri, rewarewa, fuchsia and kowhai. Some of the birds involved are the tui, bellbird, kaka, parrakeet and silver-eye. Nearly 65 per cent, of our forest plants have succulent fruits attractive to birds. Of the important trees only the kauri, cedars and beeches do not rely on the birds for seed distribution. Several birds perform this function, the most important being the pigeon, not only on account

of its varied tastes and. voracious appetite but also by virtue of its size, which enables it to swallow the largest fruits. The little silver-eye, on account of its large numbers, is also an important factor in seed distribution. Anyone prepared to feed these birds during the winter can find out for himself just what kinds of berries they feed on. When living near a patch of bush I set up a bird table on which I fed silver-eyes on sugar and water from April to August. The ground beneath the bird table was left undisturbed except to remove any weeds. The following April the following plants were lifted from an area of three square feet: 85 pittosporums (kohuhu and tarata), 18 large-leaved coprosmas (karamu), 19 smallleaved coprosmas, 5 lancewoods, 3 ivy trees (orihou), 10 marble leaf (putaputaweta) and 4 whiteywood (mahoe or hinahina).

If these forest inhabiting birds are so useful we cannot quarrel with the law which gives them, with the exception of the silver-eye, absolute protection. But something more than a law is required.. To give the birds active assistance we need to practise forest protection in the form of . fire control and the destruction of opossums and deer. . We need, too, to develop an active campaign against those direct enemies of bird life such as the wild cat, the rat, the stoat and the weasel.