Wildlife man’s bid to save Ashley’s endangered birds

Press, 5 December 1985, Page 21

Wildlife man’s bid to save Ashley’s endangered birds

By

MARGARET BAKER

Black stilts, wrybills, and blackfronted terns may soon be able to wander the expanse of the Ashley riverbed without fear of their nests being destroyed by the effects of gravel extraction, motor-cycles, exotic vegetation, and river and flood control works.

This is the hope of a Wildlife Service officer, Ken Hughey, who has proposed to the North Canterbury Catchment Board that a scientific reserve be established on the Ashley River. Ifl it is accepted, the Ashley would become the first river and its habitat in New Zealand to be protected by such a reserve status. “Part of the Ashley is of outstanding value to wildlife/’ Ken Hughey says. “A reserve would mean protection for birds which are fast becoming endangered species.” Braided rivers in New Zealand support a specialised bird assemblage, including the wrybill, black stilt and black-fronted tern, which are regarded as endangered species by the Wildlife Service. These bird communities exist primarily along the eastern South

Island, and the Ashley carries a breeding stock of all the main riverbed bird species.

A recent study by Mr Hughey found the skm section of the river west of the Rangiora traffic bridge to the Okuku river confluence to be the most critical nesting area for the birds. He has proposed that this be the area of the reserve.

“Bird densities there are very high, birds coming back year after year to nest in exactly the same place,” he says. “Now, some of the birds are being frightened off by the intrusion of vegetation, trailbikes, and a changing riverbed due to mechanical works. The birds’ range for nesting is shrinking.” The. nesting season begins in September and continues through to about the end of December, and this is the period Mr Hughey is

particularly concerned about. “Some of the birds are so few in numbers that once one pair has been frightened off their chances of survival become very small.” Birds that nest within the skm area also include the banded dotterel, pied stilt, South Island pied oyster-catcher, black-billed gull, pipit, Caspian tern, black shag, kingfisher, black-backed gull, welcome swallow, Australasian harrier, paradise shelduck, white-faced heron, and spur-winged plover.

Mr Hughey, who has colourbanded many of the birds, found that all the known wrybills (six pairs) on the Ashley nest within this area, and it also houses the only black-billed gull colony on the river.

The major threats to the birds’ survival and nesting habits are the effects of gravel extraction, recreation, and encroachment of exotic vegetation. If gravel extraction is left uncontrolled, as it was in 1983, it can have a severe impact on birds, especially colonial breeders, says Mr Hughey. During that season a black-fronted tern colony and a black-billed gull sub-colony deserted the area because of gravel works during breeding. The works can disrupt the natural riverbed and nesting areas and frighten the birds off.

By creating shallow pools with gently sloping banks, and clearing vegetation from islands, carefully managed work can enhance feeding and nesting habitat of birds. Mr

Hughey says that restricting the period of shingle extraction to January through to August would cut down the impact on breeding birds.

Recreation could also be minimised during the nesting period, he adds. The area he has proposed for reserve status is used by many people for trail-biking and fourwheel driving, walking and running dogs, shooting, fishing, swimming, picnicking, and bird watching.

Each has caused disturbance to birds and nests, and some have caused chick deaths.

Trail-bike riding is the biggest problem. Fishing and shooting has had isolated impacts, although in 1983 shooters were caught killing protected black-billed gulls in the area. Swimming and picnicking in general do not conflict with bird habitat use, as they are most prevalent from December onwards. “Good public relations and a continuing educational process are needed for these impacts to be minimised and successfully managed,” says Mr Hughey. “People often don’t realise the effect their activities may have on the birds; it’s something we have to make them aware of. It’s possible to organise things so nobody will miss out on their fun.”

The third major threat to the birds is the encroachment of exotic vegetation. Most of the birds prefer to nest on an area of bare shingle, with little or no vegetation present, but lupin, broom, gorse, and willow are slowly invading the riverbed and reducing the available nesting areas. Vegetation also harbours predators, such as rabbits and ferrets, who prey on eggs and

chicks. Spraying and clearing would reduce the vegetation and increase the area of prime nesting habitat, as well as promote Catchment Board aims of keeping a clear flood-way between river control lines, says Mr Hughey. River control and flood protection works also interfere with the birds’ nesting habits. The area is suited to the birds because of the wide riverbed and large number of small braids, but downstream of the railway bridge the riverbed has been reduced in width by flood control works.

Mr Hughey says that as yet the works had not greatly modified the proposed reserve area, and provided further work was concentrated on existing sites there was little likelihood of major impact to the birds.

The proposed reserve land tenure is controlled by the Catchment Board, which also manages the water resources of the Ashley river. The Wildlife Service has responsibility for the conservation of endemic bird fauna.

Mr Hughey suggests a joint committee of Catchment Board and Wildlife Service staff be formed to draft a management plan for the area before the reserve was proposed to the public and submitted to the Minister of Lands. A committee including three from each organisation and a board member to chair the committee would be appropriate, and would leave the casting vote with the Catchment Board.

He proposes that the reserve be given a scientific designation, which offers considerable scope for wildlife habitat in the area, without compromising Catchment Board aims.

“And, hopefully, the birds will keep coming back.”