Is the welsh harlequin bill sexing method 100% accurate?

[BackyardAnimalsDucks]

I have two welsh harlequins and I was wonder if the bill method is correct. I looked and they are apparently both females. Is that true? Also when do male ducks reach sexual maturity?

 

[Miss Lydia]

@MagpieDucks

 

[cheezenkwackers]

It worked for the two I raised but I read that it depends on who you get them from. I believe male ducks start mating at four months but aren’t fertile until a few months after that.

 

[Duckworth]

My harlequins all turned out to be the gender that I expected based on bill color. Sexing by bill color is only reliable for the first few days from hatch.