IN ALLIANCE

Nelson Evening Mail, Volume LXIV, 12 January 1931, Page 7

IN ALLIANCE

BIRD AND TREE -r»,' . INSECTS ARE GOOD AND BAD THE NEEDED .CHECK As an agent in pollination and seeddistribution, and as a defender of tree life against insect life, the bird, and particularly the Now Zealand . native forest-dwelling bird, lias a mission ot his own. No birds, no forest. JNo forest, no birds. Forests or plantations are always liable to attack, unless the bird bodyguard is present. Such attacks, (writes Mr W. R. B. Oliver. M.S.C., in “The Timber Growers’ Quarterly Review’ ) came from two main groups, fungi and insects. Boring insects create points of entry for fungi that otherwise would be repelled by the bark. The policemen of the bark are native birds, which also cleanse the branches and hover over the lightest foliage. A FEATHERED INSURANCE Writes Mr Oliver: “Were it not for birds, insects, which multiply at a prodigious rate, would soon get the upper hand in all types of vegetation, but most damage would be done in those plantations or fields where but one kind -of crop is grown, because here the abundance of food of the one kind favours the multiplication of those insects to which that particular ciop is the normal food plant. In a forest it is well known that certain insects destructive to wood, such for instance, as the puriri grub, which is the larva of a large moth (Charagia virescens), prey on only a few species of trees, and consequently have little effect _ on the forest as a whole. However, in a plantation where only one species or a few' distinctly allied species are grown, it would be disastrous were it attacked badly by an iniurious insect. It is essential, therefore, that the risk of such a catastrophe be minimised, and there is no better insurance against disaster than stocking the plantation with birds. Given a variety of forest birds such as can bo provided by the native species almost every kind of insect pest would bo effectively attacked. “The forest insects have been studied from an economic point of view by Dr. David Miller. . Of the indigenous species of insects, over 50 per cent, are, according to Miller, dependent on plant food, and of those which can be classed as injurious, 80 per cent, lire forest dependants. There are, however. in New Zealand more species of exotic than of indigenous injurious insects, the proportion being seven to three; find of the imported species 18 per cent, arc associated with forest trees. INSECT IMMIGRATION CAN’T BE STOPPED “It is practically impossible, to prevent injurious insects being imported into the Dominion. The inspection of fruits and plants has closed the door to a good many, but forests pests do, nevertheless, come in on timber unchallenged. Insect attack all part? of the tree and in various ways. Some feed on the roots, others suck the sap from the leaves, and still others bore into the wood, not excepting some of the hardest timbers, such as the indigenous puriri and- 1 maire. Not only are trees damaged to the extent of rendering them useless for timber, but in cases they may be lulled outright. The fores-; ter has, therefore, a very real enemy in injurious insects. “More than three-fourths of the indigenous forest birds and most of the imported species are insect eaters. Even those species such as the tui. and bellbird, which are furnished with brushlike tongues, especially adapted for sipping nectar, feed on insects all the year round. Fortunately, these species . are common in many localities, and a little patience on the part of the observer will soon be rewarded by the sight, perhaps, of a bellbird diligently searching the crevices of the bark of a tree for insects. Other very careful investigators of the trunks of trees are the little New Zealand tits, while some species, such as the fantails, take their prey op the wing.” 'THE MAGIC OF POLLINATION After pointing out that introduced species like the hedge-sparrow, and even the sparrow, make greater or less raids upon insect life, Mr .Oliver refers to the processes of pollination (transfer of pollen from the male flower to the stigma of the female flower) and seed-distribution. As to the former: “Among certain trees, and especially those 1 belonging to the class, Gymnosperms—which includes all cone-bearing trees, such as pines, cypresses, redwood, and the kauri, as well as certain kinds with fleshy fruits such as rimu, miro. totara, and matai —pollen is produced in vast quantities and is freely distributed by wind. While this is undoubtedly a factor in pollination, it is a wasteful process, as a small proportion only of the pollen produced finds a lodging on the female cone. A far more efficient method is that in which pollen is transferred from plant to plant by insects or birds. Bees and , other nectar-seeking insects assist in this work, but among New Zealand trees arc several-, that are especially adapted to have their pollen carried from flower to flower by birds. Such are the various kinds of rata (including pohutukawa), puriri, fuchsia, kowhai, and rewarewa. “Flowers adopted to have their pollen transferred bv birds are of two main types. In one type, seen in the puriri, kowhai, and rewarewa, the corolla forms a long tube with anthers exposed at its mouth. At the base of the tube is secreted nectar which forms no small part of the food of many species of birds. Insects may be debarred from- obtaining the nectar by a close growth of hairs in the corolla tube, as is seen in the puriri flower, but birds easily push their beaks beyond this obstruction and so reach the sweet nectar. In the second typo of flower the petals are small and inconspicuous hut the stamens are long and numerous, forming a kind of brush as in iho ratas. Within the circle of stamens at their base is secreted the nectar. It is a strange fact that is well worthy of note, that bird-pollinated flowers arc usually red in colour, though in some eases —as, for instance, the kowhai — they are yellow. BADGE OF A FAITHFUL TUI “A bird sipping the nectar from either of tho two types of flowers mentioned must, because of tho nectar being placed right at the base of the corolla or the stamen, brush its forehead against the anthers, and in doing so sonic pollen will collect on tho frontal feathers. As the bird visits different flowers the pollen will be carried from one to another, some of it being deposited and remaining on tho sticky stigmas; and thus cross-pollina-tion will he effected. It is a common tiling to see a tui or bellbird with its forehead covered with yellow pollen derived from the rata or flax, or even of blue pollen front I lic naUvc fichsia. Dandruff is embarrassing. Prevent it with Brice’s Dandruff Prescription.— Necs, Chemists, Hardy street.

This is an absolutely sure sign that it is carrying out a useful and essential work for the forest trees.”

Some insects help the birds to pollinate, but in the distribution of seeds insects tflke no part. Birds eat fruits and transport seeds which are distributed far and wide, unbroken and unharmed, to wait.—perhaps for years—for tlieir germinating opportunity. Thus do forests regenerate. By the action of birds, winds, and streams, distribution is effected of speds capable of remaining viable for a long time. A gap in tlie forest is thus quickly filled by trees, and young ones replace the fallen. Tho native birds can be brought hack by planting more trees (including birdfeeding trees) and by restroying noxious mammals rat, stoat, weasel, deer.