I am new to this also but I believe the duck would get lonely if the only one. I would say get at least two minimum if you can.I was interested in getting some chickens, and I kinda want a duck too. Would the duck get lonely by itself, or will the chickens be enough company.... Also can the duck eat what the chickens do or do they need a different diet?
I use flock raiser. Can be used with chicks, grown ups, ducks, and chickens. You just have to supplement calcium for layers.
Now, a few days ago I'd say the duck would be perfectly happy with just chickens. Then I saw the cutest thing ever. I had an extra drake and I didn't feel like processing him, so I brought him to this retired guy who just likes to have some backyard poultry to look at. He had a single duck already (a female) in with chickens as companions. I put my duck down next to his duck to see how they would react. Immediately, they both started duck talking to each other so excitedly. They were running around each other and quacking/male duck sounding constantly. It was not aggressive at all. It was what I would call happy and excited. My duck is young and not sexually mature, so it wasn't that either. After they got acquainted for a minute, the female duck kept quacking at him and showing him where all the good weeds were. They did not leave each others side the whole time I was there. I really just about died from cuteness. So I will say two ducks will be happier than one, even if they have chicken companions.