Emboldened geese invading city centre face population control

Wednesday, 17 June 2020

What can the council do about too much geese poo?

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.

Canada geese numbers are rising fast, and the public may be told not to feed them.

The city council's head of parks, Andrew Rutledge, said numbers increasing year-on-year were causing concern.

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Canada geese on the Avon River in central Christchurch.

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'.

Lake Ellesmere has a large Canada goose population.

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 Ngā 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.

03052020 NEWS Photo: JOSEPH JOHNSON/STUFFCoronavirus COVID-19 Botanic Gardens in Hagley Park covered in leaves with Canadian Geese taking over where the humans used to sit. Day 41 of the Covid-19 pandemic government ordered lockdown operating at Level 3 in New Zealand country wide.

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.

Goose guano makes using the boat ramp by the new Avon Loop riverside pathway a tricky business.

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.

Rutledge said the city council was exploring culling, contraception, non-lethal chemical food pellets, hunting, trapping and relocation, removing sources of human food, managing habitats, and scaring measures such as laser pointing.

As well as the problems of bird strike and fouling, the birds could transmit disease and parasites, and contaminate waterways, he said.

Crossland's reports say almost 4000 birds were counted in the city in May, up from about 3000 in February, a number that could rise to 5000 during winter.

Large numbers of the geese have also been counted on Lake Ellesmere, Lake Forsyth and Akaroa Harbour.

The reports say flocks in the city had 'transitioned from small groups to quite large groups' and 'invaded' more sites.

'Although 'don’t feed the geese' signs are in place in some areas, unfortunately the public are still feeding geese and they’re rapidly habituating to people – meaning they’re no longer shy and will boldly occupy any riverbank or nearby urban park space they have success in finding food,' the reports say.

'That’s a pretty problematic scenario as management options are few.'