How to determine who is laying?

[Mamahen2104]

Hello again I'm back at it with my wacky questions!
So I have 4 ducks, a runner, silver appleyard, muscovy, and magpie/pekin (we think?), how can I tell who is laying based on behavior or looks rather than picking them up and feeling pelvic bones? I don't like to have to chase after them and pick them up because it probably stresses them out. They're all about 6-8 months old and I know my silver appleyard is laying but I got a mystery slightly green smaller duck egg. I think it's my runner but I'm not sure

 

[Texag87]

I have never done it but people have said to put food coloring on the vent. Different colors for different ducks .

 

[Mamahen2104]

I've never heard of that! Is that safe for them?

 

[WannaBeHillBilly]

Slightly greenish!? - That sounds like a Runner Duck's egg.
My Fawn & White Runners lay faint greenish eggs.

 

[Ratchnick]

Food coloring is ok but you still have to catch the duck.