One of Lake Wanaka's top, free tourist attractions has left for the winter.
A growing population of endangered and unusual-looking great crested grebes has been a point of difference for the Wanaka Marina, in Roys Bay, during the breeding season.
They have featured on various tourism and bird-watching websites.
But now, 12 parent birds and their 31 new chicks have gone, probably to warmer lakes in Canterbury, leaving just one pair.
Lake Wanaka Guardian John Darby has been providing the birds with floating platforms on which to build their nests.
In previous seasons, when there were no nesting platforms, the birds did not breed in Lake Wanaka.
Mr Darby told the Otago Daily Times yesterday his plan was to encourage the remaining pair to stay around over the winter and act as decoys for birds looking for somewhere to nest in the spring.
That had proven successful last year and the decoy pair even produced a clutch of eggs in midwinter.
Mr Darby said one of the difficulties of studying the migratory habits of grebes was how to mark individual birds.
Because they spent almost their entire lives in the water, and could barely walk, it was unrealistic to use leg bands, which would seldom be visible, Mr Darby said.
''It's been suggested the grebes are the most aquatic of all birds.
''Essentially, the only time they ever get out of the water is when they're laying and incubating eggs.
''Otherwise they never come on land.''
Mr Darby said he had been providing the Department of Conservation in other locations with information about how to build floating platforms for grebe nests.
He is also regularly visiting Lake Hayes, near Queenstown, to study grebe numbers there.
Those birds have yet to fly north for the winter.
There are estimated to be between 300 and 400 grebes left in the South Island.
They are fully protected.
Asked about the risks to grebes during the duck-shooting season, Mr Darby said: ''I'm always very apprehensive about that.''
