A watch is being kept on Lake Wanaka for a great crested grebe with a plastic ring around its neck.
A photograph of the grebe was posted on a social media pageby John Wattie on New Year's Eve.
Mr Wattie wrote the ring could mean the grebe was "doomed to starvation''.
"The poor grebe became frantic trying to get rid of the ring, swam in high-speed bursts, jumped right out of the water, but nothing it could do would displace the ring so it could pull it over its head.''
Lake Wanaka Guardian John Darby, who has been leading an effort to encourage more grebe to nest and mate around the Wanaka marina, said the bird's plight had only been brought to his attention in the past few days.
However, volunteers were now keeping a lookout for it.
Mr Darby had seen the bird while doing his regular checks of grebe nesting sites.
The ring was well down the bird's neck, at water level, and largely obscured by feathers, he said.
While he could not see it clearly, it did not appear to be causing the bird immediate problems.
Mr Darby said he could not be sure what the plastic ring was but he had picked up a bangle from Eely Point that was of a similar size and shape.
If the bird returned to the nest it was building at the marina, an effort would be made to catch it, Mr Darby said.
"I think we will need to call on a lot of resources to do that, but it is possible.''
Grebes in New Zealand are "nationally vulnerable''.
The numbers nesting and breeding on Lake Wanaka have risen substantially since Mr Darby began his conservation efforts a few years ago.
Great crested grebe
Podiceps cristatus australis
• Fully protected.
• A 2004 survey found no more than 350 adult birds in New Zealand, mainly on Lake Heron, Canterbury, and Lake Hayes, near Queenstown.
• Also known as Australasian crested grebe, southern crested grebe, puteketeke and kamana.
• Freshwater diving bird.
• Adults 50cm long and 1.1kg.
• Legs set far back are efficient for swimming but awkward for walking on land.
• Can dive for up to a minute.
• Feeds and sleeps on water and builds floating nests.
• Elaborate courtship rituals.
• Carry their chicks on their backs.
• Can fly long distances, mostly at night, on small wings.
• Predated by dogs, stoats and other swimming predators.
Sources: wikipedia, Department of Conservation, http://notornis.osnz.org.nz and nzbirdsonline.org.nz
