We have just added a male and female duck to our yard of chickens. They seem happy after only 2 weeks on the land, and just two days ago the female started laying. I am a bit worried, the male duck has started twitching his wing and opening his mouth most times. It's like he has something stuck in his throat. He is drinking from the pond and eating OK.. Can anyone suggest what may be the problem or is this what ducks do?