I've got a kingfisher at my pond and I really enjoy it. I'm told (this might be wrong) that they are very territorial so it's unlikely that you have more than one - and it's almost certainly a female - that is "ruling" your pond.
So, they can't be eating all that much. And they mostly just eat small fish. Some websites I've looked at say they eat only fish.
Around here, racoons love to dine on crawfish.
But they are part of a parasite cycle (black grubs that appear as black spots) and for that reason I don't want them with my high value fish.
