Cayuga or cross?

[chicky-little]

I just had some ducklings hatch and 2 out of the 6 have these little yellow patches under their beak, but no where else.
We do have a cayuga and a welsh harlequin drake, however the cayuga never allows the WH to breed the ladies from what we have seen and before we got the cayugas we never had any successful fertlization from the WH as the sole drake with our previous ducks.
Could these ones be a cross or is this normal with cayugas?

 

[Cayuga momma]

It sounds like a cross. Even the full black ducklings could be crosses since the extended black gene is dominant.

 

[chickens really]

Crosses I'm thinking...

 

[FluffTheDuck]

I think it’s a Cayuga— when I was little we had cayugas with that patch right there and they turned out to be complete cayugas.