Its funny you ask this because just an hour ago I took a picture of the flock sharing a food dish at dinner time and I marveled at how well they are getting along. See picture below.
So, I had chickens for about 1.5 years (4 hens, 1 rooster) and then hatched 3 chicks in ealry April. Then in late May I got 2 2.5 week old ducklings. My coops are Eglu, meaning that the birds only sleep and lay eggs in there. I have a fenced and netted in corner of the yard for them to play in all day. They free range around the yard, i.e., outside the enclosure, every day for some time, and my hope was that ultimately everyone would get along and even sleep in the same coop, leaving one for "emergency quarantines" and stuff. One coop can house around 10 chickens and the other 4. It worked out.and is working but not exactly as planned...
The first night I had the ducklings, I put the chicks to sleep outside in the smaller coop while the adults were in the larger one. Mornings, I took the chicks out of the coop and they had breakfast in the yard and free ranged all day. The adults stayed in the enclosure unless it was free ranging time or someone escaped..they are crafty. When it started getting warmer, I had ducklings outside in a large cage but where everyone could see eachother. Eventually, I opened the door to the cage and let them decide when they wanted to explore and make friends with the chicks. Yours are already friends, right? The ducklings would retreat to the cage if the chicks were overly rambunctious. Also, the ducklings werent out every day due to weather and also in the evenings. It got chilly (no feathers yet) and I brought them in to the brooder. But, I let the adults out to free range with the chicks in the evening.
I noticed that during the day when the ducks were out (which became more frequent and longer as the summer set in), the ducklings rarely were in the cage and preferred a covered spot next to the fence where the adult chickens were. This was their nap and preening space and they appeared to want to be near the rest of the flock. They didnt love the chicks coming and eating their pellets all day, but they were rather chill and tolerated it. I just kept adding more food as they ate considerably more than the chicks. And they got the extra vitamin B supplements, which then everyone benefited from I guess. They didnt let the chicks push them around. In the evenings, they followed the rooster around and mingled with the hens, but primarily just watched them from a safe distance. Their shear size helped them in integrating. As Muscovy, they were at least as large as all the hens, even as ducklings. During free range times, which were also sometimes during they day, I let everyone mix..also the dog and cat were always roaming around, kids might have been on the trampoline, etc.
My approach was probably one of familiarity and safety. All birds could see eachother, even when separated, and I made sure that everyone got enough to eat. Also, I didnt leave anything to chance for a few weeks. I was around doing yard work inconspicuously when they were out together to make sure the rooster and hens werent too agressive with anyone and that no one fell in the pool, stuff like that. The ducks tend to do their own thing. They swim, nap together, forage, eat, and repeat. Recently, if the ducks feel the chickens are too close for comfort, a peck in the butt clears things up. I felt that this separation early on, having the ducklings in the house and the chicks in the yard and in a different coop than adults at night, helped me see if the ducklings brought any sicknesses in and if everyone was healthy. I was always paying attention to poop and looking for sneezing. Its been a few weeks now since all, the adults, the ducks, and the pullets, are roaming around outside all day and sleeping outside. The sleeping outside part was where reality diverged from plan.
First, ducks have different feet and I think prefer to sleep on flat surfaces in a nest. The chicks easily chose to sleep in the big coop and their transition from the small to big coop was rather painless.The roosting bars of the small coop had to be covered to make it easy and comfortable for the ducks and they sleep on a bunch of straw because...
Second, ducks are a mess. Their poop shoots out like a water gun, and is far more liquidy than chicken poop.
Third, my ducks are currently heavier than any chicken I have and are still growing. I could probably get them to be willing to sleep in the same coop as chickens but they take up so much more space than simply adding 2 more hens (or roosters for that matter).
So all in all, the ducks are far bigger and there is limited sleeping space, they require different bedding, have poop that doesnt dry up nicely on woodshavings under roosting bars (seemed like more frequent coop cleaning), and need a roosting bar cover...it was more than three strikes against my plans for them to sleep in the same coop. The nail in the coffin for this idea was also finding out that ducks often like to sleep outside. I cant leave the coop door open and risk losing all birds..so, my final arrangement is....
I changed the fence of the enclosure to beta fence or metal cloth (was recommended here for ducks) to give the ducks more protection if they want to sleep outside but still in the enclosure. I have a table so that they can be out of the rain, or I might keep the small coop door open. This should probably be decided on based on predators. We have very few.
The ducks are in the smaller coop with a plastic desktop protection mat hiding the rooster bars, which is covered in hay. Due to the poop, I have to add or exhange hay once a week, hosing it down. I didnt have time this weekend and adding abunch of hay was good enough. I keep the door open all day to help things/poop dry a bit.
Currently, I wake up the ducks first, and they eat breakfast in the yard. Then I prepare chickens food.and water and close up the enclosure. Then, I let the chickens out. The coop door can be opened from outside the enclosure. The chicks are safe and happy with the adult birds in the enclosure. Sometimes the chicks visit the duck coop during the day and look around but they dont linger. As the ducks get older the poop freuency appears slightly reduced but the "quality" is still the same. Its like poop straw mudpies in there if Im not careful! Anyway, the ducks free range all day because that is where the kiddie pool is and frankly, they still sleep a lot of the day. Their poop has the advantage that is dissolves quickly in rain or with a brief squirt of the hose, unlike chicken poop in grass. They also dont commandeer my potted plants for dust baths. So, Im fine with this arrangement that the ducks free range alone all day until the chickens join them. The ducks go into their coop wilingly like clockwork at 9pm.
@WannaBeHillBilly wrote that ducks can be mildly trained which Ive found to be true.
The chickens burn the last seconds of daylight (sunset post 9.30pm) and go to bed much later. Even if the ducks go to bed later as they get older, being in different coops allows the ducks to avoid being disturbed by the nightly chicken pecking order ritual of finding the best sleeping spot in the coop.
Im still deveoping and I hope that this long winded answer is helpful in some way. I found familiarty (boundaries that still allow everyone to see eachother) and gradual increasingly longer time together worked best for us. If you have ideas, Id love to hear what works for you when you try it.
Here they are, relaxed at dinner time.
