I don’t think he would kill the ducklings, because he ADORES our chicks and other ducklings(incubator hatched). Taught them how to forage, dust bathe, etc. he may though just because those two would be with them..
I have two broody Muscovy hens in the shed. They’ve got lots of eggs and are somewhat defensive(just warnings, not aggressive). They told my male guinea off once for trying to peck the eggs. Now he is terrorizing them and won’t leave them alone day and night. They refuse to leave the eggs so...