Paradise shelducks are causing headaches for farmers in Northland by chomping their way through their crops.
But Fish & Game is advising farmers to get a head start and invest in bird-scaring devices to discourage them.
Northland officer Nathan Burkepile says the birds are becoming a real nuisance.
"This time of the year, with the dry weather, the chicory crops have not come in completely yet and when they're just coming out, the paradise shelducks tend to eat the new sprouts and pretty much they can eat out a full paddock of chicory," Mr Burkepile says.
"So we're trying to assist farmers in reducing that damage."
Bird-scaring cannons are the most effective method, if farmers get on to it before it becomes a problem, he says. They can be rented from Northland Fish & Game, or bought for about $600.
It's also important farmers keep the ducks off any reservoirs on their property before they begin to moult in January and can't be moved on, Mr Burkepile says.