Forest and Bird's Bird of the Year competition is often heated and fraught with controversy and just three days in, this year is no different.

While people are only allowed one vote in the competition and must choose their favourite of New Zealand's natives, one Christchurch citizen decided that didn't apply to them.

They cast more than 100 fraudulent votes for the white-faced heron, Bird of the Year co-ordinator Kimberley Collins has confirmed.

"We're not mad, just impressed that someone cares enough about New Zealand's native birds to rig the competition," she said.

One batch of the illegal votes were cast in the dead of the night, between midnight and 1am on Monday. A second set came at around 11am on Tuesday.

The fraud was uncovered by Yvan Richard, a scientist at Dragonfly Data Science in Wellington.

He said he was tracking the votes with a computer programme he also used in the US, UK and New Zealand elections.

"So I thought why not do it for Bird of the Year? It's really exciting to see the votes coming in at real-time," he said.

"I noticed there was a big spike for the white-faced heron at about midnight on the first day of voting, so I let Forest and Bird know."

Ms Collins said they've taken security precautions to make sure this doesn't happen again.

"We suspect their plan was to sneakily increase the heron's numbers by a few hundred each night while we were all sleeping. Thank goodness Yvan was watching."

It's not the first time the competition has been plagued by fraud. In 2015, hundreds of fraudulent votes were cast for the kokako by two overenthusiastic voters.

The competition aims to raise awareness of New Zealand's unique native birds and the threats they face.

Newshub.