This is one "duck" that definitely doesn't need to be thrown any bread.

A Mandurah woman's post this week on a popular Perth Facebook page has drawn widespread interest - and no shortage of hilarity - after she thought she'd spotted a "black duck" on a grassed area near a lake.

That's not a duck sunning itself by the water in Mandurah. Credit:Facebook

On closer inspection it turned out to be a large sex toy.

WAtoday is unaware if the woman used the type of abductive reasoning made famous by American poet James Whitcomb Riley to determine it wasn't a duck: "When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck."