That is the sound of ducks.
Are you picturing these birds fishing or floating on a nice lake somewhere?
A normal reaction to be sure -- but these ducks are different.
They live on a grape grower's land in South Africa.
The Vergenoegd LowWine Estate is in Stellenbosch.
And the ducks are employees of the winemaker.
About 500 white, black and brown Indian runner ducks make their home on the grounds.
They hunt and eat insects and other animals that can damage grape vines.
The birds help protect the plants naturally.
This saves the winemaker from having to use poisonous chemicals against such pests in his vineyard.
Corius Visser runs the land.
"We call them the soldiers of the vineyards.
They eat all the small insects so we don't have to spray for any pests in the vineyards.
They keep them pest-free. They are the caretakers."
The ducks are tall, which means they can reach up and eat insects on the vines above the ground.
In addition, the people who run the vineyard use the waste from the ducks to make fertilizer, which helps the grapes grow.
Merle Holdsworth was visiting the vineyard and saw the ducks.
She praised their orderliness.
"It's amazing how they behave themselves, walk in a row, and it's like they're in the army," she said.
The ducks get up in the morning and go to the vines to eat the insects.
At the end of the day, they go back to their home and eat some bird food provided by the winemaker.
Yodell Scholtz works in the vineyard and takes care of the ducks.
"It's almost like raising your own children, so I enjoy it a lot," he said.
I'm Dan Friedell.