You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
Department of Conservation contractor Paul Van Klink and his conservation dog Hoki surveyed the Route Burn last weekend and found six adults and 10 juvenile birds, which was on a par with previous years, he said.
Whio are one of only four duck species in the world which live all year round on fast-flowing rivers.
"If the ducklings are big enough, the parents can take them higher up to a side creek, but real heavy water can wash away nests and even kill adults."
Mr Van Klink said it was not known what would be the impact on whio of more frequent and heavy rain events because of climate change but Doc rangers had observed whio feeding from water ponding beside a track.
Mr Van Klink this week gave a Doc-sponsored talk on whio and his search dog Hoki, who is retiring at the end of this season.