A rarity for my region — a Yellow-Billed Duck

I was taking a walk (as I always do) on Saturday morning around my neighbourhood. There's a couple of ponds around and on the bank of one of those ponds, I saw two strange ducks. Their bright yellow beaks really caught my attention and I took a couple of photos, but I thought they were just strange mallards.

Upon further research once I got home, however, it turned out that these ducks were, in fact, Yellow-Billed Ducks! They are only native to some parts of Africa. Not sure how or why they came here to North-Western Germany! Maybe escaped pets?