New Zealand has the second-highest number of introduced bird species of any country. Many became pests, damaging agricultural crops or threatening native birds. In situations where native bird species have declined, some introduced birds play a valuable role in pollinating flowers or dispersing native plant seeds.
Numbers
One hundred and thirty bird species were brought to New Zealand. A few were kept as caged or domestic birds, but most were deliberately set free to live in the wild.
Forty-one species successfully established wild populations. They included 16 passerines (perching or song birds), three pigeons and an owl – nearly all from Europe. From Australia there was the magpie, the kookaburra and three species of parrot. There are also 16 introduced waterfowl and game birds.
Successes and failures
Some species were introduced several times before becoming established, while others were ultimately unsuccessful.
For successful establishment, the habitat and climate had to be suitable, and the birds adaptable. Most successes were in land cleared for farming, which was similar to the British countryside from which many species came.
Some, such as the house sparrow, bred prolifically and quickly reached high numbers. Others, such as the cirl bunting, remain rare.
The many species that were introduced but failed to become established include the English robin, the nightingale, the emu and the Solomons cassowary.
Why introduce birds to a new land?
Sentimental reasons
To settlers from Great Britain, familiar birds were a sentimental reminder of ‘home’. They missed the well-known tunes of British songbirds, especially since land cleared for farming was unsuitable habitat for most native species.
Stopped in their tracks
In the 1860s armyworm caterpillars reached such great numbers that trains sometimes came to a standstill, wheels spinning, because the tracks were made greasy by their crushed bodies. In one account from Rangitīkei, a train was brought to a halt by caterpillars rushing across the rails to reach a nearby field of oats. While the crew cleaned and sanded the rails, the stationary engine and carriages became covered, inside and out, with thousands of caterpillars.
Utilitarian reasons
By the early 1850s crop-damaging moths, caterpillars, beetles and grasshoppers had built up in huge numbers, due to the expansion of agriculture and horticulture. One Hawke’s Bay farmer resorted to driving his sheep across infested pasture to trample the coloured carpet of caterpillars.
While some native birds ate insects, they would only forage in farmland if there was bush nearby. As the bush edge was pushed back for agriculture, they had less effect as pest-controllers.
In the hope they would eat agricultural pests, farmers introduced insect-eating birds such as blackbirds, thrushes, starlings, sparrows and magpies.
Acclimatisation movement
The first introductions were haphazard, private efforts. From the 1860s regional acclimatisation societies began a more coordinated approach.
Promoting acclimatisation
Charles Hursthouse was an early advocate of acclimatisation. In 1857 he wrote that rooks, magpies, starlings, sparrows, thrushes and other small birds should be introduced, as well as game birds for hunting. He also proposed the introduction of rabbits, hares and deer – all of which later became serious pests.
Acquiring birds
Advertisements were placed in English newspapers, offering payment for live birds of the desired species. The species were selected partly on how easily and cheaply ships’ captains could acquire the birds, and their likelihood of surviving the voyage.
Bringing birds to New Zealand on sailing ships was challenging. Voyages from England could take four months, through a range of climates and frequent rough seas. Most birds died en route.
Selecting species
Some acclimatisation societies had criteria for selecting suitable species. For example, as well as eating summer insects, they had to be able to live on other foods – such as fruit, seed or grain – to survive in winter. They had to be non-migratory, so they would stay. And they had to be prolific breeders to have a significant impact on the insect problem.
Crop losses
Hidden in the criteria was a recipe for calamity. Farmers soon discovered that the plagues of insects were replaced by platoons of birds stripping their grain crops and damaging fruit.
Grumbles within the ranks
From the 1860s acclimatisation societies were at the forefront of introducing birds ranging from small birds, such as sparrows, to large game birds, such as pheasants. But it wasn’t long before some of their own members were complaining that small introduced birds had multiplied so rapidly they were competing with the introduced game birds for food.
Plague of small birds
Within 15 years of their introduction, there was a coordinated effort to control small European birds by laying out poisoned grain, paying a bounty on eggs and heads, and shooting them. The little owl was introduced in the early 20th century to prey on small introduced birds.
