My 2 month olds and my 3 month old ducklings in one big flock. These are Cayuga Swedish mixed ducklings. I incubated one group and mama duck hatched the others. She abandoned the ducklings' so I raised them. Now they are all independent and going to the big pond. A few will be going to a new home this week.
My veterinarian wanted to raise some ducks for his pond. So I am giving him 4-5 from this flock.
This year I stopped incubating eggs by August. It is just too hard for me to raise baby poultry in the winter. So much easier when the weather is warmer. Some of my hens do go broody in the winter, and I have to watch them on hatching days. I isolate the mama's and babies in a separate coop when this happens. That way mama can do her job and keep her weight in the winter.