One duckling- and very early
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Do you still have eggs to hatch? She'll be happier with friends, close in age to her. If she's the only one to hatch, I'd see if I could locate another duckling or two similar in age so she has somebody to grow up with and not be duck lonely.
A month difference in new ducklings is huge and she'd likely not do so well with the month olds - she's too small for them.