Duckling housing question :)
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The ONE you get now will have to wait until your spring ducklings are ready to go outside as well. A single duck outside by themselves is a very unhappy duck.
As a single duck, it is going to bond to you.
Depending on where you are when when "spring" is, that rabbit cage could be quickly too small for a growing duckling unless that's just for while you are sleeping. Have you determined what you will need to do in order to keep your single duck happy/content at being a single duck?
I'd suggest getting 2 now or waiting until spring to get the ones you want.