In all centres of settlement the animal life is almost as much due to foreign immigration as the people are; but observers cannot tell this fact without some assistance, and one of the difficulties with which all embryo naturalists are met is to know which plants and animals are native and which are introduced. Let me illustrate this.
Living as I do in a suburb of Dunedin, just outside the Town Belt, I observe in my walks that in this neighbourhood certain species of birds are very common. They are house-sparrows, blackbirds, thrushes, starlings, and hedge-sparrows. These are all forms which have been introduced from Great Britain. Almost as abundant, but more erratic in their occurrence, are wax-eyes (or twinkies) and goldfinches--the former a somewhat recent immigrant, apparently from Australia, and the latter introduced from Britain. Less abundant in varying degree are grey warblers, tomtits, fan-tailed flycatchers, chaffinches, greenfinches, an occasional yellowhammer, and a little brown owl. The first three are natives, the rest are introduced. The native bell-bird (or korimako) visits the gardens from time to time, especially when the trees are in flower; while occasionally in the outlying districts one hears or sees a tui or a morepork: these are all natives. In the more open country introduced skylarks are common, as are the native ground-larks, or pipits. On the seashore are numerous species of birds, but these are all indigenous species. On still nights one often hears the black swans flying overhead in their migrations from one sheet of water to another: these were introduced from Western Australia.
About the house are occasionally a few mice, and in town brown rats are common. These are not kept in check by the dogs and cats which are common in many houses. During the nights hedgehogs roam about the gardens, and are far more common than unobservant people have any notion of. All these and the other mammals met with, such as horses and cattle, sheep, goats, pigs, and rabbits, were originally introduced, mostly from Britain.
When I go to work in the garden I turn up numerous earthworms, nearly all belonging to introduced species--unless I start to trench in new ground, when I come on native species. The wood-lice are introduced; so are the earwigs, which are so common in the north end of Dunedin; so are all the slugs and snails. The bees and humble-bees are introduced, as are the large drone-flies which visit so many of our flowers in autumn and early winter. Nearly all the plants in our fields, orchards, and gardens, cultivated ones and weeds alike, are of foreign origin; so are the aphides and scale insects which infest them. The flies which infest our houses and carry dirt and disease in all directions are foreigners; so are the borers which destroy our houses and furniture; and so also are bugs, fleas, and lice, which are harboured in dirty surroundings.