THE PRESS FEATURE Survey squashes belief that ducks come to town for shooting season

Press, 13 May 1981, Page 21

THE PRESS FEATURE Survey squashes belief that ducks come to town for shooting season

By

DERRICK ROONEY

The thousands of ducks which congregate on the Avon River in May — to escape, many city people believe, from the shotguns of hunters — would probably be there even if there were never a shot fired at them. This is one of the surprising preliminary conclusions that have emerged from a privately-sponsored survey of duck populations and behaviour in central Christchurch by the Canterbury Museum’s zoologist, Mr Geof Tunnicliffe, and the Botanic

Gardens park ranger, Mr Jim Baggstrom., The two men have spent many hours of their spare time in the last couple of years locating and observing nests, banding selected birds (with bands they paid for out of their own pockets), and patrolling the riverbanks to make counts. The survey was motivated partly by concern for the welfare of the birds, and partly by the handy opportunity afforded by the park for a wildlife survey. For Mr Baggstrom, who is noted for his work in treating injured ducks, it was an opportunity also to supplement the general survey of wildlife- in the gardens that has been made over several years by himself and the gardens education officer, Mr Jeremy Rolfe. . Some 200 nests have been

included in the study, and these are estimated 'to be two-thirds of the nests in the area. One of the first conclusions to emerge was that the native grey duck is now very rare — at least in this part of the country. The overwhelming majority of ducks seen during the survey have been the introduced mallards, or mallard-grey hybrids. The reasons for these feathery mixed marriages are not clear yet. Though many people believe that the mallard is taking over because it is a more aggressive bird than the grey, the observations of Messrs Tunnicliffe and Baggstrom indicate no basis for this belief. What they have seen indicates that grey drakes are well able to hold their own in a squabble with mallards.

A surprising observation is that many of the. drakes remain near the hens during the nesting period, and on one occasion a drake was seen actually sitting on a nest. There is some evidence, too, that mallard and grey ducks, contrary to popular belief,- often mate for life; it is well known that the native paradise ducks form permanent attachments but the others are widely believed to be more casual. A staggering conclusion drawn from the survey is that despite the abundance of cover in the Botanic Gardens and on the riverbanks, and the apparent lack of predators, the Hagley Park reaches of the Avon River

are an insecure and unsuccessful nesting ground.

The survival rate of Avon ducklings is close to zero, despite the romantic notions held by many people about the Avon as a breeding ground, and the hardy-annual photographs in the city’s newspapers of cars on riverside roads stopping for cross‘ing ducks. The observations made by the two men have shown conclusively that the city has .no self-supporting colony of ducks. The population on the Avon is maintained solely by newcomers which come in from other districts every year.

Even if the people of Christchurch do not recognise this, the ducks do, because it is during the nesting season in early summer, when the Avon’s duck population reaches its lowest ebb. The huge flocks that winter on the river go elsewhere to propagate themselves. The reasons for this can be summed up in a single word: predators. Water-rats and eels take a few ducklings, but the major predators are humans, or associated with humans.

Children have been seen attacking ducklings with stones or sticks; adults have been seen doing the same, or shooting ducklings with air rifles; and ducks have been found with nasty stab wounds. Mr Baggstrom found one unfortunate bird impaled

on a stake and left to die slowly.

Canoeists on the river also have to shoulder some of the blame for duck deaths, according to Mr Tunnicliffe, who says he has seen canoeists pursuing broods of ducklings up and down the river until the birds were so exhausted that they were unable to climb out on to the bank.

In many cases the canc ists were well meaning — they believed they were herding the ducklings back to their mums. But good intentions did not make their actions any less fatal. Whether this predation is a major reason for the wholesale move into the trees by the nesting ducks of Hagley Park is a matter for conjecture, but it is quite clear from the survey that the ducks have been going wards; 25 per cent or more of the nests studied’were in trees, not in the traditional sites among tussock, rushes, or flax.

A mystery about the tree nests for which a possible answer has been found is: how do the ducks get their ducklings, unharmed, from a

nest six metres or more up in the air down to the waterside?

The supposition, supported by occasional observations of grey ducks by ornithologists elsewhere in the country (this species does commonly nest in trees), is that the parents simply push their offspring out of the nest, and most of them survive the fall. A few may break their necks, but these losses pale into insignificance alongside the toll exacted later by predators. Duck numbers on the Avon between the boatsheds by the hospital and the Fendalton Road bridge dwindle rapidly at the end of winter, and by September-October the winter population of close to 12,000 is down to 200, sometimes fewer — the lowest count was 175.

The build-up begins in late summer, about January, but the numbers really expand dramatically in late April and May. The migration coincides with . the duck-shooting season, and popular belief has it that the ducks come in to the city to dodge lead poisoning. There may be a bit of truth in this, but it is

not the w-hole truth, because although more years of observation are needed before dogmatic statements can be made, the survey so far indicates that the ducks come in for food first and shelter second. The food is acorns, from the many oak trees planted in Hagley Park and the adjoining Little Hagley. This year the duck-shoot-ing season started early and beat the migration, but in other years covered by the survey the ducks have begun

to come in to the Avon well before any shotguns have been legitimately fired at them. According to Mr Baggstrom, it is possible to determine the rate at which the Avon acorns are ripening by following the ducks.. And he says it may also be no coincidence that the first successful liberation of mallard ducks, after several failures. were made about the same time as the oaks in and around Hagley Park reached maturity.

In spring, when the fruit and nuts of the Botanic Gardens run out and the urge to mate comes upon them, the ducks leave for more congenial nesting sites. Messrs Baggstrom and Tunnicliffe have no hesitation in placing acorns at the top of the ducks’ winter menu. The residents who stay behind in summer subsist during the warmer months largely on bread handed out to them by visitors to the park and gardens.