Here are some of my mobile pens, but admittedly they all have problems and I wouldn't necessarily recommend anyone to replicate them. Maybe in the future we'll design one I have no problems with. Also, they are not predator-proof at all and so would not work for most people and most circumstances.
One is a chain-link dog kennel, about 9' by 8' I think. I couldn't find any pictures I already had of it. I could take one, but anyway, it's nice and sturdy, but not the easiest to move.
Then this is one of the chicken coops:
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Muscovies can handle jumping in and out of it. I've kept ducks in it before, but right now I'm only keeping chickens in it. Also difficult to move.
Then there's this one:
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I like this one. I wish it had some siding, though, because I use it for ducklings and chicks a lot, but they need a windbreak, and there's no shade in the mornings and evenings. It's fairly light, but adding siding would make it a lot heavier. So we just lean pieces of wood against it.
Then these two:
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These are super light! However, the tarps already need replaced despite only having been in use for 3-4 months. I used them for CX broilers, for a broody with ducklings, and now they're in one of our far pastures as a night pen for some new ducks that are in quarantine. My main issue with them is that they're very small and can only hold a few ducks.
I also have one other PVC hoop pen that's similar to this but quite a bit larger and with a PVC base frame instead of wood.