Yes yes yes!!!!!!!!
ALWAYS...no matter what, use bio security!
It doesn't matter if they come from your nicest next door neighbor or from miles away in another state, you need to isolate them from your flock for at least 3 weeks, preferably a month if you can.
No If's, Ands, or Buts!
There are lots of links on here for integrating new ducks/chickens into your flock and many different views but everyone should isolate any new birds for the appropriate time and also make sure to totally sanitize your hands, shoes, clothes after handling them.
Whenever I've gotten new birds or started another flock with new chicks in a coop, I make sure to do my regular flock first and then after washing up and putting new baggies over my shoes I go into the new flock. I totally wash up again and take off the baggies outside, put into garbage and change clothes before doing anything else. I never cross contaminate between flocks.