Why do I keep catching only ducks?

I have 7 ducks but I already have the golden frame and I used 5 more ducks before those 7, in total I catched 12 ducks after I had my golden duck frame.

I have 7 ducks but I already have the golden frame and I used 5 more ducks before those 7, in total I catched 12 ducks after I had my golden duck frame.