Not sure this is related but I have a duck that had seizure's when she was 1 to 2 months old almost every morning for weeks she would be on her side I would get here warmed back up and she was fine all day... anyway when all the girls started laying she never did. on the 2nd season about once a month or so I would find a egg that was round and the size of a quarter. She is my funnest most special duck "Lucy" but I do believe all the seizures damaged her reproduction organs. The boys usually ignore her and chase around all the other girls for mating. Its like they know something we don't. Her eggs are mostly all thick shell with no yoke. I believe all her eggs were damaged in her first few months. Some reproduction problems can go all the way back to the incubation problems, to hot to cold not enough cool down not enough air. They are born with all the eggs they will lay. Like all animals, they have a set number of potential eggs in their bodies at birth. Ok so its cold out and Im stalling.