Bold geese invading city
Contraception and ‘‘don’t feed the geese’’ signs are among suggested ways of tackling a fast-growing Canada goose problem in Christchurch.
A recent population explosion means as many as 5000 of the introduced species could be on and around the city’s waterways this winter, triggering concern about disease, fouling, and risks to biosecurity and aviation.
The city council’s head of parks, Andrew Rutledge, said numbers increasing year-on-year were causing concern.
Council was ‘‘keeping a close eye on the matter, as well as what is being done overseas to manage the issue,’’ Rutledge said.
Council ecologist and ornithologist Andrew Crossland said in a series of internal reports that the increase was not a blip and ‘‘we appear to be looking at some problematic new trends’’.
The unprotected birds were partly attracted to the central city and Botanic Gardens by people feeding them, and the quiet of the lockdown may have ‘‘emboldened’’ the geese, Crossland says.
After arriving from the high country and Banks Peninsula, the birds have spread across city waterways including the newly built stormwater storage basins around the upper Heathcote River.
Crossland’s reports say while they do not want high goose numbers at busy areas like the central city and Nga¯ Puna Wai sports hub, council’s ability to use methods like shooting or poisoning was ‘‘clearly very limited’’. The reports suggest erecting ‘‘please don’t feed the geese’’ signs and having council rangers patrol parklands and talk to the public.
Last month
residents
complained of goose guano badly fouling the new $2 million Avon Loop walkway, nicknaming it the ‘‘poop loop’’. Despite council contractor CityCare cleaning the area, the mess returned within days.
Some residents have suggested the rising goose population is scaring off native ducks, including the small diving scaup. There are also concerns that the cleaning washes bird droppings back into the water, increasing contamination.
The population problem is also boosting the bird strike risk at Christchurch Airport, which must pay for bird scaring and habitat control near runways.
Professor Jim Briskie, a behavioural ecologist at Canterbury University, said while overpopulation already existed because of lack of predators, redzoning and dairying had likely worsened the problem.
Canada geese were introduced to New Zealand by hunters over 100 years ago and numbers in Christchurch have been monitored since the 1980s.
Briskie said redzoning had flanked the Avon with undisturbed green lawns in the city, while dairying had created lush pastures in rural areas. Both habitats were attractive to geese, he said.
While the geese could be shot year round in rural areas, tracking had shown the city birds stayed local ‘‘which is a problem’’, he said. Briskie, himself a Canadian, said the geese and eggs in their natural North American habitat were eaten by foxes, coyotes, wolves, bears, racoons and skunks.
At a meeting called by Environment Canterbury (ECan) in 2015 with Christchurch, Selwyn and Waimakariri councils, Ngai Tahu, and Christchurch airport, all the parties agreed to pursue a plan to manage the growing Canada goose population.