I have rescued one lone duckling. I do not know the breed etc. I am just trying to grow it into adulthood when it can then (hopefully!) join my flock of 17 ducks. My only concern is that it is a LONE duckling. I have it in a recycling container with a mirror, towels, food, water, stuffy and a heating pad. I can bring it to work with me (cool right?!?!) so it doesn't have to spend hours alone. It is allowed daily tub swims in a paint tray and I take it outside daily to play in the grass (contained) so it can hear my other ducks. My question is "Do I need to do anything else for the duckling (Peep-Peep, for now)? And When is it old enough to join the rest of the flock?" Thanks! I don't typically "do" ducklings as I have a dog who is quite the hunter, but once the ducks are bigger than she, she doesn't bother them! 
