West Yorkshire Police are appealing for anyone with any information on the crime to come forward.
Two men, both in their early 20s, were involved in the incident, which took place to the rear of Blenheim Way, Castleford at around 7pm on Saturday, May 11.
The pair lured the ducks across a pond before attacking and killing the animals with a catapult.
In a post to Facebook, the West Yorkshire Police Wildlife and Rural Crime Team said: "Suspects both white males early twenties one wearing a gillet.
"One had bright ginger hair and facial hair.
"Second male dark haired clean shaven."
Anyone with any information on the incident is asked to contact West Yorkshire Police on 101, referencing crime number 13190244808.