The America's Cup has forced a colony of threatened red-billed seagulls to up sticks and find a new home on Auckland's waterfront.

The birds had been breeding at an old boatyard which is being turned into a new ferry terminal to make space for the Cup challengers.

Environmental consultant Paul Kennedy set about using eight 3D-printed decoys to get the roughly 1000 birds to nest in a new spot, and said the birds appeared to have taken the hint by late August last year.

The decoys had been set in concrete into a freshly cleaned metre-wide ledge on Wynyard.

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A red-billed gull colony at Wynyard Wharf that has been turned into a new nesting sites using 3D printed gulls. Photo / supplied
A red-billed gull colony at Wynyard Wharf that has been turned into a new nesting sites using 3D printed gulls. Photo / supplied

"One of the people in the office next door on the site looked out and the first gulls had actually sat down right next to the decoys and so from there, the number just grew as the breeding season went on," Kennedy said.

By early December there were 942 adults, 97 recent chicks known as fluffies, and 508 fledglings - good news considering the birds' "threatened" status with a national count of about 28,000 pairs.

Auckland Council senior regional advisor Tim Lovegrove said the birds' decline was starkly illustrated by what he used to see on Cuvier Island, off the east coast of the Coromandel Peninsula.

"You'd stand up on top of Cuvier and you'd look out to the horizon and see the boil ups of the big trevally schools, driving the shrimps to the surface and the gulls would be streaming out from the colony, out towards the horizon and feeding on the shrimps.

"Around the nest sites within the colony the ground was just pink with the remains of these shrimps."

"You don't see the big boil ups like you used to and we just wonder, could this be a bit of a canary in the coalmine telling us something about our fisheries.

"We fish these stocks down to a certain level but as far as seabirds go, that level could be far too low for them to survive."

Kennedy said that was one reason why having an active colony in the middle of the country's biggest city was so special.

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"To be able to try and manage and keep natural New Zealand fauna and flora here is quite important. To be able to do this is just one element of knowing that you don't have to step out of Auckland to see some of New Zealand's coastal species, I think it's quite neat."

Kennedy and Lovegrove hoped the red-billed gulls would become a valued attraction as the development of Wynyard Point continued ahead of the Cup races in March 2021.