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YES! Drakes are naturally very rough when mating-they tend to take their sweet time and wrestle their partner down, wherever, whenever, whoever. Lot of times they end up putting their female (assuming it's a duck)'s head underwater and have the potential to kill them. I've heard of them injuring chicken hens, and even killing them.
Edited To Add: He only has one mate? If so, perhaps this is his way of telling you that he needs more girls. However, it is possible that no matter how many females you give him, he'll still try to mate the chickens. It's hard to say...