Lonely Rouen duckling

[NeeNeesFarm]

Had a young duck hen abandon her nest forcing us to bring eggs inside to keep in incubator. Only one precious baby hatched.
Now at a month-old it is still far too cold at night to have her sleep outdoors in the hut (we don't use heat lamps) we want to start getting her socialized. When is a good age to start letting her be with the flock without constant supervision and without a divider?

 

[Amiga]

When she is about the same height as the adults - it is still best to go slow. Have a meet-and-greet, but supervised. After a few of those, if it is going well, let them spend longer together till you are sure there will be no rough stuff.