Increasing numbers of Canadian geese are potentially adding to the Christchurch City Council's woes.

The council has voted to accept the sculptural gift "Diminish and Ascend" in the Botanic Gardens by Auckland artist David McCracken, which costs up to $760 a month to maintain.

Citizens and community staff member Brent Smith says the money goes toward keeping the sculpture clean, as birds cause significant deposits.

But Councillor Tim Scandrett voted against the gift, saying council needs to take a realistic look at ongoing maintenance costs.

"We do have the Canadian geese expanding, so the mess they leave is considerably more than ducks, so just be aware it's coming, so it will probably blow out that budget too."