Brian Rudman: Sparrows are around, but flocks thinner

Like the golden weather of childhood summers, flocks of squabbling sparrows are, it seems, a thing of the past. In parts of Auckland anyway. In other suburbs, nothing seems to have changed.

Last week's column about the sudden disappearance of sparrows from my front yard brought a flood of sightings - and explanations.

Road kill was the first suggestion, coming from a colleague who spotted a carcass while wandering up Shortland St.

It will come as no surprise that the Ministry of Agriculture and Forestry's aerial blitz on the painted apple moth was high on many people's list of suspects.

The argument is that the spray killed the bugs that sparrows eat, causing the birds to die of hunger.

The problem with this is that even with spray drift, my home is a good kilometre from the extremities of the killing zone. And it's hard to believe that a starving sparrow would just sit down and fade away.

More likely, it would be tapping on the nearest window asking for bread.

What's more, a colleague in Devonport, which is far from the spraying, reports that not one sparrow turned up to rip into her grass seed when a new lawn was recently sown.

Grass seed starred in several replies. A Glenfield resident recommended I scatter grass seed at my place. That would guarantee they swarmed back for a feed. That's what just happened to him.

Taking it a step further, one finger-pointer claimed it was the city council's fault. It was deliberately using poison-coated grass seed on new grass berms to drive seed-eaters into an early grave.

There's nothing I like more than a good conspiracy theory, but sadly this just didn't fit my case - our berm being many weedy years old. Nor did it fit the facts.

After a gasp and the promise of a full investigation, a council spokesman got back to assure me the seed - a mixture of rye brown and fescue - was not treated in any way with anything.

He wondered, I suspect tongue in cheek, whether the problem might have been that the council's seed was so good and wholesome the birds just over ate, fell down and never got up again.

Another variation on the poison theme was that cafe owners - one was named in particular - put out bait to rid their sugar bowls and outdoor areas of disease-carrying birds.

I suspect this was true, but it hardly seemed the full answer.

The most interesting theory was that the decline of sparrow populations was linked to the fall-off in backyard vegetable gardening.

But it didn't fit the facts around my way either.

There's been little sign of such activity here for years. The only crops I've laboured with over the years have been a few herbs, some frustratingly quick-seeding lettuce and a half-dozen chilli plants each summer in old plastic buckets.

The wax eyes regularly turn up to harvest the aphids and other creepy crawlies, but in the front yard sparrow colony there's been little interest.

Maybe they took one look at my poor imitation of a real garden and gave up, because others tell a different story.

Out Clevedon way, one long-term resident says the spread of lifestyle blocks into the farmland has resulted in a sparrow population explosion. They're attracted by the vegetable gardens of the newcomers.

They've become so virulent - woops, I meant numerous - that since his cat died he's been reduced to building wire-netting shelters for his young crops.

He says the sparrows are not fussy eaters. Baby silver beet, new beetroot leaves, radish leaves, beans. You name it, they'll try it.

His Mt Albert-based father - a keen vegetable gardener - has similar problems.



None of the above satisfactorily explains the sudden die-off of my front-yard colony. And why a correspondent living adjacent to the Grafton Gully motorway can proudly claim a backyard full not only of sparrows but of wax eyes, fantails, kingfishers, blackbirds, doves, tui and thrushes.

The best theory came from a Department of Conservation official. He likened it to what happened in the rabbit population after the introduction of the crippling rabbit calicivirus in 1997.

In the case of the sparrow, the new killer disease was a new strain of salmonella typhimurium infection, called DT160, which emerged in Canterbury in 1998.

It quickly spread through the country, causing severe food poisoning in humans and death among sparrows - the main carriers - and other animals.

In the first wave of infection this included a horse, a kaka, a blackbird, monkey, fantail and cat.

Now endemic in the local sparrow population, DT160 is likely to act like the rabbit calicivirus, flaring up and killing whole colonies, he says, except for a few who are born with or develop immunity. Then the cycle will repeat itself.

Like the golden summers of youth, he suggests the days of great sparrow flocks are gone for good.