Lori,
Can you put your ducks in a safe place until you catch the killer? you could set a live animal trap, or put a chicken or duck in a wire cage and circle it with traps. hamburger with poison or glass works too, as long as a neighbor dog can't get it. I know it may be cruel, but I have had coyotes wipe out my entire flock before I set up the aviary. This is the time of year they take more farm animals to bring back to their babies. Once a predator finds a good flock, they will keep coming back, until the have all of them.
These are solutions that I know, maybe you might think one that is more humane. That is why I spent the money on a predator proof aviary, I could not even kill a darn Coyote! What a sap I am!
Anyway I will have a good hatch in 2 weeks, you can pick the ducklings you like, and I can ship them to you. I have been getting nice magpies and spotted. Mary is just getting the perfect round spots now. She will be beautiful. Any ducklings you choose will be free to my mentor of course.
The two ducklings due on Wednesday were not loosing water like they should. I put them in a dry incubator, and they seem just right now. They are in lock down at 30 humidity. do you think this is ok? I can't wait so switch to my new incubator, it is very accurate at keeping the temp. and humidity just where you want it. no need to fiddle with it when indor temps fluctuate.
I just don't see calls flying away. My Mandarins flew off, but came right back when they discovered that there is no duck food or fresh vegetables served outside the aviary.
Peach I will start collecting eggs for you when you are ready to hatch again. My ducks are laying like crazy. I had to get a big cabinet incubator to keep up with them. It has gravity circulation. is that ok for ducks? it also puts in fresh air every 4 hours. It keeps the temp. right where you want it.
hope you find the culprit! 
