Philippa Stevenson: In defence of the magpie

Magpies are over-loud, over-abundant, over-territorial and, regretfully, over here.

The Australian immigrants attack people and harass other birds so it's no wonder many people dislike the black and white birds with the distinctive wardle, oodle, ardle song.

Whole careers, many a hobby and plenty of ratepayers' money have been devoted to trapping and killing the swaggering brutes in the hope that the effort would give our native birds a better chance at life and the dwindling bush tucker.

Now, a just completed, four-year, nationwide study of the effectiveness of regional council magpie control programmes has provided some facts about what does and doesn't work on the interlopers first released by acclimatisation societies in 1864 to combat pasture insects.

In combination with the control study, a Waikato University doctorate student, Dai Morgan, has observed and collected reports of magpie attacks on other birds, and documented magpie behaviour in their own social circle.

Such research has never been done before, not even in Australia where, remarkably, magpies are responsible for more attacks on humans than any other wildlife.

That's some record among Australia's legion of ferocious or poisonous creatures, which range from spiders to crocodiles.

Morgan has determined that magpies attack 43 bird species. On top of the hit list are harrier, blackbird, thrush, sparrow, kereru, white-faced heron, skylark, bellbird, tui, pipit and chicken.

More importantly, he discovered that only a few magpie attacks result in death and that mostly they just force birds that like the same food as they do to move on a short distance. Most victims are other introduced species.

Another significant finding is that magpies do not attack and kill birds in their nests - a major cause of native bird loss for which harriers, rats, stoats, weasels and possums are responsible.

Morgan's study of magpie social behaviour is just as revealing. Big flocks of magpies, made up largely of juveniles, tend not to be territorial, so they rarely chase other birds. Mating pairs, which do vigorously patrol their home patch, are the most likely to chase other birds - and people. They are most aggressive in their breeding season between July and December.

Landcare Research scientist John Innes co-ordinated the magpie control study by regional councils in Northland, Bay of Plenty, Waikato, Wellington, and Southland.

Councils trying to reduce magpie numbers can spend up to $21,000 a year, but the study results suggest the effort is doing little to enhance the lot of native birds.

Although a slight recovery of a few native birds were found in some areas after magpie kills, the result could be attributed to a number of other factors. Introduced species - the competitors for magpie food - recovered the most.

Magpies are, Innes said, social climbers with a temperament that "makes every day a bad hair day. They are over the top".

If a territorial pair (the ones that chase other birds) are removed the vacancy is quickly filled by another upwardly mobile couple.

"It's a black hole of effort trying to control magpies. No one is undertaking large-scale eradication. It is too hard. Magpies are here to stay."

It's likely that in time magpie numbers will meet some equilibrium - a balance between them and other species.

Fortunately, the research suggests that will not be greatly at the expense of native birds.

"They don't help native birds but magpies are not the big crims," Innes said. Instead, they have probably got such a bad press because they are big, showy, noisy, and - it must be said - Australian.

Their aerial dogfights in broad daylight may be highly noticeable, as are there attacks on people, but in the main they are harmless.

Meanwhile, out-of-sight and under cover of darkness an underworld of serious killers is taking the heaviest toll on native birds. Adept tree-climbing ship rats, along with stoats, weasels, possums and cats, are getting away with murder.

Innes said if people wanted to ensure native birds could peacefully hang around their gardens then it would be wise to kill "that pesky pair of magpies roosting in the macrocarpa by the tractor shed".

And to kill the next pair that invaded the gap, and the next. The large flocks might as well be left alone.

To make a significant difference to native bird life, local authorities and others should target control efforts at the night time pests - most effectively around birds' nests during their breeding season.

The snap of a rat trap will do most to bring native bird song to our ears.

And we'll just have to get used to it being joined by a harmless bit of wardle, oodle, ardle.

* Email Philippa Stevenson