A lecture, illustrated by lantern slides, on "The Role of Birds in Nature," was delivered before the Stock Inspectors' Conference in the Royal Society's rooms, Elizabeth Street, by Mr. A. G. Hamilton, F.L.S.
The lecturer pointed out that the disturbance of the balance of Nature by the cultivation of the land by man had far reaching effects. Clearing destroyed the natural haunts of insects, which were decreased in numbers, as also were the wild birds that lived upon them, and that again led to an increase of herbage destroying grubs in gardens and cultivation generally. There were no birds entirely obnoxious, nor entirely beneficial, the lecturer explained. Usually their usefulness or the reverse was conditioned by their surroundings. Parrots, for instance, did great harm in orchard and grain-growing areas, but in sheep and cattle country they were not at all harmful.
Birds, on account of their high blood temperature, and their activity in flight ate enormously, and were always on the hunt for food. It had been estimated that in the cultivated areas of the United Kingdom 135,431,328,000 insects were destroyed each year by larks. The total number destroyed by all birds could hardly be imagined, but had been estimated at two quadrillions, weighing 558,035,718,571,428½ tons. Similar calculations had been begun in Australia. It was estimated that the ibis ate 1400 grasshoppers a day.
The curlew was most valuable in the number of pestiferous insects it destroyed. The mopoke, he went on, was useful in destroying stick insects, which sometimes killed gum trees by denuding them of leaves. The peewit, by destroy ing snails that were injurious to sheep, was of great service to farmers. The eagle might or might, not be more valuable in destroying rabbits than harmful in killing lambs, but it was a very fine bird. The black owl and the eagle owl were also known to kill rabbits, and preferred them to native marsupials.
The willy wagtail, Mr, Hamilton said, was almost a stock inspector in himself, and might always be seen hopping about over the back of a horse or cow, searching for vermin on the animals' skins. As showing the bird's lack of fear of domestic animals and even of man, Mr. Hamilton showed a photograph of a wagtail's nest built on the lashings with which a clothes line was bound to a prop. The bird used to sit on the line and watch the housewife hanging out the clothes. The swallow, Mr. Hamilton said, was an indefatigable catcher of flies and beetles, and he had once seen a battle royal between a swallow and a large dragonfly (horse stinger). They appeared very evenly matched, and both were wonderful fliers; but the fly escaped in the end, because of its unique ability to fly backward.
The blue wren, the lecturer went on, did no harm, and, with the silvereye, was a force against the aphis, although the silvereye did a lot of damage to grapes. The "Twelve Apostles," the bird with the greatest number of aliases, and the cuckoo, which is the only bird that will eat hairy caterpillars, were mentioned. The bee-eater, often called in error the kingfisher, was a great insect destroyer, but unfortunately could not distinguish between pests and others. Often it would fly about outside a hive, and snap up every bee that approached, or came out. The emu was not known to be of any use, and had been charged with kicking and killing lambs. Probably the emu's worst feature was the agitation it caused among horses, sometimes rendering them unmanageable.
The sparrow and starling, two imported birds, were mostly pests. The sparrows ate plums, grain, and other things. Attempts to poison them were disastrous, as they preferred to die in a piggery, if one could be reached. Then the pigs ate the sparrows and were in turn poisoned. The starling did good in sheep country by destroying maggots on sheep, but they were unpleasant birds when they nested in a house roof, on account of the way in which they scattered lice. The honey-eaters, such as gill-birds, spine-bills, parakeets, and green lecks were instrumental in pollenating various plants, such as the banksias, grevilias, spider flowers, waratahs, sword lilies, flowering gums, and apple trees.