Fish & Game's 16th annual nationwide count of the Australasian shoveler duck, known as spoonies for their distinctive flat bill, is under way.
Matthew McDougall from Fish & Game said the ducks were a prized game bird but it was not known exactly how many there were in New Zealand.
He said today's survey would be done with the help of volunteers, including Ornithological Society members in about 260 sites around the country.
Mr McDougall spoke with RNZ from Rotorua today where he was helping with the survey. He said estimates from last year's count put the population at about 14,000 but shoveler ducks were "very mobile" which made them difficult to count. Banding has shown they can travel large distances.
He said the largest estimated population last year was about 3000 of the birds recorded at Lake Poukawa in Hawke's Bay.
"These counts just tell us whether the population at the sites where we're counting are going up or down. The idea is that we count enough ponds to give us some sort of gut feeling, or surety that the population isn't being decimated or anything like that," he said.
Mr McDougall said the survey was done on the same day to avoid any double-counting, and an index was being built to gauge shifts in numbers over time. They were counted at this time of year following the hunting season when they are starting to "mob up" as part of their breeding behaviour.
He said the counting methods used were "pretty simple".
"We go out in vehicles or even in boats and kayaks armed with binoculars to spot the birds.
"Shoveler like shallow ponds where there are lots of invertebrates to feed on, using their shovel-like bills to sift the aquatic insects from the water."
In the South Island, shoveler are a common sight in the central South Island's coastal wetlands but they are also found in the Mackenzie basin high-country, Mr McDougall said.
He said Fish & Game also carried out random surveys of hunters which showed if harvests were sustainable.
"Most Fish & Game regions have a daily bag limit of two or three birds per hunter and while they are plentiful in some areas, most hunters never get near their limit," Mr McDougall said.
Fish & Game said the birds made up a minor part of the annual game bird harvest but were "highly prized".
The shoveler is a native species but is not endemic to New Zealand.