The flight cages are portable in the sense that they do not require foundations or embedded piers etc. You need a flat area (I like 3’ additional all the way around so you can use a ladder anywhere for maintenance, but if limited like I was, you’ll have to do your maintenance from inside the cage) I laid out a 4’wide run of 1/2 x 1/2 hardware cloth around the perimeter (2’ inside the cage and 2’outside) and built the pipework frame on that, prevents anything digging in or out. I have the 30’ cage shown below and a 50’ cage designed in the same fashion but with a double door at each end, available to any non-profit that wants them. Most of the parts (maximum length of 12’) can be transported either trailered (not by me, as I can not back up a trailer even if my life depends on it, or in a U-haul which I have money to rent. There are some 2x4's in 20' lengths for the plywood skirt that can be transported on a lumber rack (which I have) or cut to smaller lengths. I have photos on how to construct and can be available to help but my limit is an 8’ ladder.
10'x30'x12'high flight cage
I also have the pipework for a 12’x20’x15’ high cage available. It’s a little different in that the walls slope and the top of the cage is 1’ smaller all the way around. I was not going to use it again as the 15’ height was not fun for maintenance but if that isn’t an issue for you, it did make a nice holding cage if my other flight cages were occupied. It could be rebuilt as is or modified with additional pipe and I’m happy to talk options.
8'x16'x8'high all metal cage
4’x8’ panels made of 1x1 tube steel for the framework w/ 16ga1/2x1/2” hardware cloth on the outside and pet screen zip-tied on the inside which could be removed if you wanted to use it for mammals, w/ plywood shelters at opposite ends, hardware cloth under entire cage and double door w/ padlock (not shown)