Then there are the unexpected consequences that have afflicted previous attempts to play God with animals. In the 1880s, ferrets and stoats and weasels were released to kill the rabbits that had been released as sport and bred like ... well, rabbits, at ruinous speed.
Contrary to plan, the mustelids stepped foot on this tropical paradise, took one glance at the intimidating big-footed rabbits, and decided fresh bird eggs and chicks were a much tastier - and less strenuous - diet.
They disappeared into the bush and have created mayhem with the bird life ever since.
Cats, which arrived with Captain Cook as onboard rat-catchers, were also tested as rabbit-catchers, but they also preferred rats, mice and birds.
Dr Morgan now wants to extract the cat from this messy and complicated equation.
No one doubts that kitty's menu includes a wide range of his feathered friends. But cats are also a major exterminator of rats and mice, which are also partial to eggs and birds. Removing cats could lead to a population explosion of rats and mice, which won't help bird or man.
The volunteers of Ark in the Park, the 2300ha sanctuary for native bird life in the Waitakere Ranges, appreciate the complexity of restoring lost wild life. After 10 years of laborious pest control, they're now contemplating the reintroduction of kiwi within a few years.
Between 1976 and 1986, several failed attempts were made by the Auckland Regional Authority and volunteers to reintroduce weka, North Island brown kiwi and red-crowned parakeet in the ranges.
In 1990, ecologist B.W. MacMillan concluded that the attempts had apparently failed. He didn't identify a cause of death for the kiwi, apart from the release area being too small.
He wrote that "residents' dogs and other predators near the release site at Huia probably killed most of the weka ... [while] cats and ground predators ... probably took many of the red-crowned parakeets."
Ark in the Park is trying to avoid these pitfalls, with a large territory, a comprehensive pest control programme and buy-in from neighbours. The reward has been an increase in native bird numbers, including reintroduced kokako and North Island robins. Now they're talking of kiwi.
The Companion Animal Council claims New Zealand has 1.4 million pet cats, about twice the number of pet dogs. As I discovered last year, suggesting stricter controls over either triggers the sort of hysteria President Obama sparked when he called for tighter gun regulations.
Yet in Australia, companion animal controls are much stronger than ours. In Queensland and New South Wales, for example, cats and dogs have to be registered, and identification chips implanted. The fee for desexed animals is a fraction of the price for entire animals.
It seems a good first step in dissuading cat - and dog - ownership. Rather more likely to succeed than lining moggies up against the wall for $5 a shot.
Meanwhile, Dr Morgan might like to fund free trips for Aucklanders out to the pest-free bird sanctuaries popping up in the Hauraki Gulf. It might be enough to persuade us of the merits of a cat-free environment.
