A "weird puking bird" with a bizarre mating dance has won New Zealand's annual avian beauty contest, triumphing after British comedian John Oliver launched an unlikely global campaign.

The unfancied Australasian crested grebe soared to an unexpected victory in the Bird of the Century ballot on Wednesday, backed by voters from far-flung cities including Tokyo, London, and Paris. 

Oliver used his popular television show to meddle in New Zealand's beloved competition, urging viewers to back the species more commonly known by its Maori name "puteketeke".

Baffled organizers were soon in a flap as tens of thousands of votes poured in from 195 countries, briefly crashing counting systems.

With a striking plumage of black, white and brown, New Zealand's online bird encyclopedia celebrates the water-loving puteketeke as a "majestic and distinctive" species.

Oliver, meanwhile, less charitably dubbed it the "weird puking bird". 

Puteketekes are known for eating their own feathers in an effort to trigger their gag reflex and throw up parasites, said competition organizer Nicola Toki from the conservation group Forest and Bird. 

"Puteketeke began as an outside contender, but was catapulted to the top spot thanks to its unique looks, adorable parenting style — and propensity for puking," Toki said.

They are also known for a strange and elaborate mating ritual which they perform with gusto but limited success — it is believed New Zealand's puteketeke population has dwindled below 1,000. 

It involves enticing a potential mate with weeds dangling from their beaks before chest bumping them and engaging in a chorus of chirps that experts have called the "growling cat display". 

"I have never identified with anything more," Oliver said.

Oliver, the star of US television show Last Week Tonight, hijacked the vote with his self-styled "alarmingly aggressive campaign" after discovering the competition was not restricted to New Zealanders.

He said he erected billboards imploring the people of Mumbai, Tokyo, Paris, and London to have their say.  

Organizers said they ended up tallying over 350,000 votes — smashing the previous record of 56,000 votes cast in 2021. 

But Oliver's meddling and so-called "fowl play" has also upset many in the bird-proud nation, with organizers forced to discard tens of thousands of suspect votes — including 40,000 cast by a single person for a breed of penguin.

Birdwatcher Michael Burton-Smith told local media the overseas votes "ruffled the integrity" of the campaign.

The good-natured competition is never short of controversy, with past polls plagued by suspicious numbers of Russian votes, and accusations that neighboring Australians were trying to rig the competition. 

The kakapo, a chubby flightless parrot resembling a green-feathered bowling ball, was disqualified from last year's competition because it had already won too many times.