Does anyone have any ideas why a duck stops eating or drinking? He is my Runner drake, about 7 mos. old and just started this yesterday. He runs with 4 pekins girls (3 now) but day bef. yesterday I found one of the Pekins dead in the pen from something grabbed her by the neck. I'm sure it was the bobcat back but it never got her out of the pen as my livestock guard dog showed up and ran it off. (he was a little late on that one). I checked all the other ducks and everyone was fine. I noticed my drake was acting quiet so thought he was grieving over the lost duck but now I don't know. I've checked him all over for bite marks, etc., find nothing. He walks up to the water bowl and just stares at it, same with the food. No runny nose, watery eyes, coughing, nothing. Just won't eat or drink. He follows his girls around the pen while they eat and drink and runs from me when I try to catch him but somethings wrong. I added organic applecider vinegar to their water in case its a sore crop. His crop feels okay, not full or anything. Poops, but very little, green with white, looks normal. Any suggestions? Should I add an antibiotic to the water? If so, what kind? Thanks. Sharon