Unusual garden birds

The pond in my meadow is just entering its third season.  It was made for wildlife, particularly dragonflies, but this wasn't quite the wildlife I had in mind.  Last week I looked out of the window to see two drake mallards walking along the drive.  I picked up a camera and when I opened the door I could see a female swimming around in the pond.  At first one of the drakes was trying to keep the other one away from her but soon they were all in the water.  The female didn't seem interested in the drakes and was either feeding in the pond or falling asleep.  Here are a few photos.

On balance I don't think the ducks will be good for the pond, so if they return I shall discourage them.