The only problem I have had with ducks and chickens together was when I had too many drakes.  They would go after the chickens and they are not anatomically compatible to breed.  If you have males and females make sure it is only 1 drake or just go withh females.

My muscovy are scared of the chickens, the chickens were first.

Yes you can keep them together. They should get along just fine. I actually new someone who had turkeys (4), ducks (4), and chickens (2-3 dozen) all living together with no problem. I've had ducks (10) and chickens (2), lie together also. Here's a picture, (this is when most of my ducks were ducklings, but they still get along fine)

Here are some more recent ones.

My Ducky LOVES his chickie babies

This was when they were young:

This was how they spent christmas day 2010 (it was stormy here in australia):

Snuggles!!!

Ducky is bigger and so little chickies love to snuggle so they hired him for protection as their bodyguard.

He watches out for other birds and runs for cover and chickies dont really know what is going on but if he is running they run too!

He stopped a neighbors cat in our garden because the cat was like *** is that big thing making weird noises?! 

He scared my little dogs because the dogs were like *** is that big thing making weird noises?! lol

Little chickies never go out of his sight; if they do he quacks coz this scares him.

Also the hen HONKS I think that, she thinks, she is a duck!  Its so cute and funny

Good day.

My flock is comprised of 50-some chickens of all breeds and sizes, 4 Cayuga drakes, 4 Cayuga ducks, 1 call drake, and a pair of Toulouse geese.  They all share the same coop (it's a converted garage) and range freely together.  I do have to keep one large waterer for chickens up higher so the waterfowl won't foul it.  The ducks and geese just gotta play in the water!

Oh good, I was just wondering about this. I have 2 Pekin Ducklings and will be picking up some chicks tomorrow.

Thanks a lot for the info!

-Lute

Yeah chicken and duck poo is great for the garden!

I empty the duck 'pond' - one of those plastic half shell pool thingys in pic above^, over the roses and WOW they have done so well.

Ducks require plenty of water so I have a cat litter box that I fill up and he even jumps in that and tries to splash.

lol It real funny to see coz he is too big and his bum hangs out. I will have to try and get a photo. 

I have a water feeder that I change mornings and evenings so its fresh and clean for them; but both chickens and ducky prefer to drink out of the duck poopie pond water EVERY TIME!!!

Silly things