Kōwhiowhio/blue duck are river specialists, one of the few waterfowl worldwide that live year-round on fast-flowing rivers. In the North Island they’re known as whio.
DOC Biodiversity Ranger Antje Wahlberg said the five-yearly census, carried out in each of the whio security sites around the country, is important for gauging numbers of the threatened-nationally vulnerable bird.
“The best time for doing kōwhiowhio surveys is either early morning or late evening when they’re more active and feeding on the river. Whio dogs, trained through our Conservation Dogs Programme, are crucial for the search.
“When it’s hotter during the middle of the day kōwhiowhio spend a lot of time roosting under large boulders so it’s easy to walk past without realising they’re there. The dogs really come into their own then as they can smell hidden birds and indicate to their handler that birds are nearby. A quick search with a headtorch under some boulders usually shows kōwhiowhio roosting in the dark.”
Dog handler teams checked the Styx, Arahura and Kawhaka river valleys as well as the Mingha in Arthur’s Pass, she says.
“The Arahura and Styx have had large floods and slips over the past four years so we were worried that pair numbers could be down significantly. However, we saw plenty of kōwhiowhio.
“In the Styx, seven confirmed pairs were found with several single birds seen too. Towards the end of the breeding season kōwhiowhio are less territorial so partners can be seen further apart from each other than earlier in summer. Several of the single birds seen were only a few hundred metres apart meaning another two to three pairs could be present in the area.”
Results in the Arahura were also similar to past years. Six pairs were confirmed between Harman Hut in the upper valley and the Cesspool near Milltown. Several single birds were also seen, representing a possible further three pairs.
Four to five pairs were seen on the Kawhaka River along the West Coast Wilderness Cycle Trail. One pair was spotted in the section of the Mingha that was checked. When the full Mingha was checked at the last census two pairs were found.
Three of the four dog handlers working on the census were DOC rangers, the other a private contractor experienced in whio survey work.
The census was supported by the Genesis Whio Forever programme.
DOC partners nationally with Genesis in Whio Forever. Since the partnership began in 2011 the number of whio pairs nationwide has increased from 298 to over 860.
Genesis’ General Manager Sustainability, Kate van Praagh, said it was great news the 2023 whio census had been such a success.
“Genesis relies on waterways to generate electricity through our hydro power schemes, and healthy whio populations are an indicator of healthy rivers.
“We’re proud to support DOC’s work in growing and tracking whio numbers.”
Whio Forever is encouraging people to look out for whio this year. This could include spotting them in their natural habitat or helping with trapping or volunteering near known whio locations.