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.