Are ducks affected by chlorine in a swimming pool?

No, but if they swim in your pool a lot, the duck poop is going to make the water murky.

Ducks and Swimming Pools are not a good combination. Pool sanitisers such as chlorine have no ill affect on the bird. Ducks like the pool environment as it is often a safe haven with clear water and unobtrusive surrounds.

The duck droppings do have a negative effect on the pool water balance and will eventually clog the filter with the creamy white paste.