If you have other ducks you do not necessarily need a friend. A friend does make your life easier though. I have had a couple single ducklings as I tried hatching Dutch Hookbill’s for the first time. I kept my last duckling in a large aquarium (75 gallon) in my house. He had a big mirror, toys l, and a stuffed duck to snuggle with. I gave him lots of swim time in the bathtub or a busboy tub (started out slowly at first), to make sure he got enough exercise. Single ducklings tend to be couch potatoes and develop leg issues and angle wing as a result. I fed mine Mazuri waterfowl which floats so he would swim for it.
I took him to school with me every week day in a canvas bag with a plastic tub inside lined with a puppy pad (shelf liner too when he was young). Eventually his head stuck out the top and everyone called him my bag duck.
Even from a young age we visited the big ducks. In your ducklings mind, you are mom and you are introducing him to the flock. I would just sit cross-legged and he sat in my lap. Eventually, I had him stay in a crate by the big ducks for longer and longer amounts of time. Eventually, he wanted to stay with them at night also. He is now, a year later, the head drake of my flock of eight. He has not suffered any social issues. I will mention that he was the only drake with 6 girls when he joined the flock.
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