We couldn't really find any way to confirm our findings without observation of males and females, but we used this question as a great way to research a subject we could not observe. My computer says very few males mate with the same females. Usually robins mate with one female a year. Robins mate with one, I checked on Grollier computer.
Robins mate almost with one girl.
I learned that from my teacher WE used Computers, interviews and bird books to fin our answers. We have lots of puddles between huge areas of snow and mud but no worms.