It's nice to hear that everyone has got a hold of their fly situation. My friends don't put sand on their floor either. They live in the high desert and don't put anything down. There are a few flies but I guess it doesn't bother him too much. He does have a few flay traps hanging around. Maybe...
Have these ducklings been left alone to fend for themselves? The ducks here all have mothers, we don't feed them anything, we let the mother take care of them.
True Grit I also have seen that posted somewhere on another forum. For them it worked, I think it had to do with them being shiny, its the shiny objects that keeps the flies away.
Finding out what kind of fly you have can help with the flies, how to get rid of them. Does it rain a lot where you are? Before I moved here we could always tell when it was going to rain, the flies always went to the ceiling. I read on another forum that a gentleman put out a cup of coffee with...
Thanks for the information WenJ, The chickens I am helping with right now are free range, so we don't have to much of a problem with flies, how to get rid of them. Have you tried fly strips in the run?