Our pond draws all kinds of transient waterfowl. We've had everything from Wood Duck pairs to Blue Herons. Sometimes they stay for a few months, like the Wood Duck pairs and other times it's just a one time thing.
For the last week we've had a young Merganser calling our pond home. I thought it would only be for a day or two, but it appears that my Call ducks don't mind the company and have welcomed the little addition. I imagine at some point she will feel the pull to fly away and look for her own kind. But for now the Calls as well as myself enjoy her company. :)