Photo: Paul Vettoretti.

Birds have a fascination for many people. From the majestic soaring of a Harrier high over the farmland to the antics of some garden species many people derive great pleasure from birds. But there are other sides to them and Rural Living considers three species and their effects on our country – one is endemic, the other a native, and the third a very obvious example of an introduced species turned pest.

Paradise shelduck

The paradise shelduck has been one endemic beneficiary of European settlement in New Zealand.

The Maori nurtured the rather uncommon shelduck by hunting them only outside the breeding season.

This conserved their numbers as a food source, but as the nation changed from forest to pasture, numbers of shelduck increased rapidly.

Like most things in nature they will go for ‘a free lunch’ and the abundance of grass and weeds suited them admirably.

During their moulting season particularly, they will raid crops, and farmers have grown less fond of them.

In some areas they have had a significant impact on pasture production, and have been found to graze white clover for preference.

During a recent study it was estimated that a single shelduck would consume around 100gm per day of dry matter on pasture.

It may not sound a huge volume, but multiplied by an autumn flock on a freshly sown paddock, you can understand farmers’ dim view.

In certain areas in the past shelduck have been hunted almost to extinction.

There is little threat to them today, but if they are perceived as a general agricultural pest, that could change.

Inevitably birds are prime carriers of disease, either biologically or mechanically and some farmers do believe that shelduck are a source of salmonella, and are responsible for greater fouling of waterways than livestock.

Being large, noisy and visible birds they are easily blamed for possible waterway pollution or disease, but faecal sampling has largely been inconclusive in proving cross-contamination.

As with most threats, a greater density of population will increase the likelihood of disease spreading.

However one pair of shelduck on a farm hardly represents a threat, but a couple of hundred could well allow enough faecal-born pathogen material to survive and be transmitted.

Australasian Harrier

Undisturbed, nature has a wonderful way of cleaning up after itself.

We are very short of raptors in New Zealand, but the Australasian harrier is a good example of a raptor-turned “vulture”.

Classified as native, it is believed that the bird has been present here even before Maori settlement, though not in huge numbers.

Normally they hunt for mammals – rabbits, rats, possums etc, but the abundance of carrion such as road-kill possums have provided them with a steady food supply.

One source suggests their choice of prey is seasonal, but in the age-old tradition of “the free lunch” a harrier with a nest of hungry chicks is not going to expend energy hunting when a vehicle has already done the hard work.

Open country is the birds’ preferred habitat, meaning they too have benefitted greatly from agricultural practices.

Although their numbers may have declined after the 1950s when rabbit control took effect, their population seems to be pretty stable at present.

Sparrow

The cheeky sparrow.

Last but not least, we come to the humble sparrow.

Interestingly this familiar little brown bird has apparently been in major decline in London in particular, but is a good example of a species taking full advantage of all human-kind has to offer.

In the Reader’s Digest Complete book of NZ Birds, the legend under the picture of the sparrow reads “....possibly New Zealand’s greatest bird nuisance”.

They were introduced in around 1867 to combat insects, by then munching their way through the colonist’s crops, but in an over-familiar story of what goes wrong with avian introductions settled down to eat the crops themselves.

By 1908 the Injurious Birds Act had them included as a most  troublesome species. Like mynas and other species capable of rapid adaptation, the sparrow has gone from strength to strength and will produce at least three broods a season.

Their habits, in entering buildings in pursuit of a very wide diet mean they are a prime source of disease and potential infection. During winter in particular they flock round chook-runs and take full advantage of all that expensive mash and wheat you were hoping to turn into fresh eggs!