I bought two muscovy hens. One is blue pied and one is silver. I asked the seller if they were pure muscovy and he said yes. However, I went outside yesterday and the guinea was chasing them (mean guinea for another post- I would re-home him if I could catch him). Anyhow, they quacked!! They don't quack other times, but I thought they never quacked. Does this mean they are mules? (It's the two on the left in this picture.) Any thoughts?