why is is that occasionally i find an egg in the box and the day after i find that it is have eaten

sometimes you get a bird that are egg eaters and i dont think there is any thing you can do about this,sometimes if the hen refuses to come out of the nest box to breed the **** bird attempts to mate with her in the box and the egg gets smashed once smashed it is chewed to dust so it looks like it was eaten it is normally the **** bird that does this

mine sometimes just throw the egg out of the nesting box