August 27, 2016 at 9:00 pm #1770narenaParticipant
It has long been said that homesick settlers introduced birds into New Zealand for purely sentimental reasons. Sentimentality was indeed a factor with such birds as the skylark but the main reason for their introduction was far more practical.
With the wholesale destruction of the bush to make farmland, New Zealand’s ecology was so disrupted that the country was overwhelmed by plagues of insects which, to use the words in an old agricultural bulletin, (1)“crawled over the land in vast hordes. They came not in regiments and battalions but in mighty armies, devouring crops as they passed along and leaving fields as bare as if seed had not been sown”. One of the few weapons the farmers had was to drive flocks of sheep over the armies of caterpillars. It was for this reason that the settlers turned their attention to introducing birds. The issue was considered carefully, utilising the best scientific advice of the day. They were the bio agents of the day.
Most of these birds were introduced during the 1860s and 1870s so they have now been here for around 150 years. As birds in the northern hemisphere continue their preciptous decline, these populations may well become important. Just as an introduced species of bumblebee was taken from NZ to repopulate the United Kingdom where it had become extinct, so birds may in future be required to do a similar job.
Recently a birder from the United Kingdom was asking birders here if they had noticed any evolutionary changes to the birds introduced from Europe, considering how long they have now been here. It is the classic Darwinian scenario, following the story of the finches on the Galapagos Islands which were so instrumental in formulating Darwin’s theory of evolution. A very small number of birds, carrying just a portion of the species genetic potential will over time change and radiate to fill the ecological niches which are on offer. Isolated from their parent birds, unlike Australian introduced birds whose genetics may be boosted by birds continuing to come across the Tasman, these birds will in time become truly our own and probably quite different from their European counterparts.
Certainly there is no need to denigrate these birds, and certainly not to persecute as has been the case with the rook, corvus frujilegis. Rooks are a minor agricultural pest, certainly no worse than say yellowhammers or sparrows. The efforts of Regional Councils under the aegis of the Biosecurity Ac have now probably exterminated the rook in New Zealand. At what cost? Persusing the online data of the Wellington Regional Council, $60,000/year has been proposed over a period of twenty years 2002-2022 at a cost of $60,000 a year to eradicate the rook. Extrapolating from this, it is costing councils around the country many millions to eradicate the rook, money which could have been spent on our precious endemic birds.
Are there plans to target other introduced birds?
1.Our Feathered Immigrants, James Drummond, 1907.
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