I have a total of 17 Muscovy ducks. I got 5 from a place that was very abusive and was able to rehabilitate them and integrate them into my flock. I noticed after they had been with us for 5 or 6 days (in the isolation yard) they would raise their heads and click their beaks. I thought this was strange. They seemed peaceful, showed no signs of distress, discomfort or pain and all in unison would raise their heads and click their beaks at the same time. Then I got another 3 from another abusive farm. It took longer to rehabilitate them. But after about 8 or 9 days they would do the same thing in unison. I finally did some research and found out that they do this when they feel comfort and are happy!! Squeak does it each evening religiously after they all have been put into the duck yard for the night and they are all full. Sometimes 1 or 2 of her original broodmates (she was one of the 5 adoptees) will join in and raise their heads and click their beaks with her. I can see she is peaceful when she does this. I thought I'd post this because I could find no thread here about this subject.