I stopped by the feed store yesterday to pick up some oyster shell for the hens but decided that 50lbs was overkill so I bought this 'Flock Block' instead. it was on sale and they said it had extra calcium in it so hopefully it'll be as good for the girls. The thing looks liek a Giant bird treat, like for a caged bird(canary, etc.). I am wondering if anyone uses these for their ducks? it's the first time i've seen them and figured the chickens would like them but not sure about the ducks.