Native Water Birds Return to Christchurch

Forest and Bird, Issue 307, 1 February 2003, Page 10

Native Water Birds Return to Christchurch

LYNETTE HARTLEY

quiet revolution is A csnsin the wildlife on Christchurch’s waterways. No longer the sole domain of bread-guzzling mallard ducks, the streams and ponds are filling with scaup and other native birds. More than 4000 of New Zealand’s population of approximately 20,000 scaup now live in Christchurch city, up from less than 100 in 1985. At least 20 other native birds are also increasing in numbers in the city including paradise shelduck, pied shag, little shag, shoveler, grey teal, coot and variable oystercatcher. At first glance Christchurch, the most English of New Zealand’s cities, is an unlikely site for a scaup comeback. For a start, scaup are traditionally believed to prefer pristine lakes well away from people. Christchurch’s waterways, although extensive, are anything but natural. They are also home to mallards — about 20,000 at last count — and it has long been believed mallards outcompete native ducks, particularly in modified habitats. In the early 1980s a handful of scaup nested on water-filled shingle pits to the northwest of Christchurch. Individuals started showing up in the city and in 1991 a single pair nested on the Bromley oxidation ponds, adjacent to the Sumner Estuary. In mid-1996 the council started controlling predators around the ponds. "We created a "mini-mainland island" for the birds, with maximum food and minimum predation, according to Andrew Crossland, ranger and wildlife management specialist with the parks and waterways unit of the Christchurch City Council. By 1999 there were 129 pairs of scaup nesting at the ponds producing around 600 young a year. These young started dispersing around the city.

In the late 1980s the council also changed the way it managed the vegetation along the city’s waterways. It no longer mows grassy banks right to the water’s edge and encourages planting of native plants. Andrew Crossland believes the taller, thicker vegetation gave the young scaup the break they needed to move into the rest of the city and compete with the mallards. The thicker vegetation gave them places to

hide and nest and encouraged more invertebrates for feed. ‘The ponds were pumping out young. That was the engine driving the population increase in the rest of Christchurch, says Andrew Crossland. The council’s policy is to back winners — the scaup were already moving back into the city and the council initiatives gave them a helping hand. Other native birds are benefiting as well. Paradise shelducks, for example, are

increasing but are about five years behind the scaup while little shags are starting to breed in the centre of the city. ‘The city is reintegrating back into the Canterbury region. It’s not a sink for wildlife any more. With the estuary on one side, and Lake Ellesmere on the other, Christchurch can become a hotspot for native birdlife just like it was for thousands of years before people arrived; Mr Crossland says.